Simulation method for concrete bridge widening structure in limited space

Abstract

The invention provides an analog simulation method for a concrete bridge widening structure in a limited space, and belongs to the technical field of analog simulation, and the method comprises the steps: constructing a multi-scale-multi-constraint coupling finite element model of a widening structure adaptive to the limited space, defining a multi-dimensional simulation boundary condition driven by the limited space, and constructing a multi-scale-multi-constraint coupling finite element model of the widening structure; and performing staged coupling simulation analysis under a limited space working condition, performing multi-objective optimization iteration on limited space constraint based on a simulation result, and preferentially screening a parameter combination which reaches the mechanical standard and has the minimum space redundancy for practical application of the concrete bridge widening structure. The simulation precision of the bridge widening structure is effectively ensured, the transformation efficiency is improved, and the engineering risk is reduced.

Description

Technical Field

[0001] This invention relates to the field of simulation technology, and in particular to a simulation method for widening concrete bridge structures in confined spaces. Background Technology

[0002] With the upgrading of urban transportation, the demand for widening and retrofitting existing bridges has surged. However, many widening projects face limited space constraints (such as proximity to buildings, narrow road clearance, and cramped construction sites). Traditional bridge widening simulation methods have significant limitations: traditional finite element models are mostly designed for open spaces and do not integrate the geometric constraints of limited spaces (such as the cantilever edge profile of old bridges and the construction clearance limit of the widening area). Furthermore, multi-scale coupling is insufficient (the macroscopic bridge, microscopic nodes, and microscopic interfaces are not associated with the parameter thresholds of the limited space, such as the minimum spacing of anchor bolts and the minimum width of welded joints). This results in the model being unable to reflect the chain effect of narrowing space, structural constraints, and variations in mechanical response. Moreover, the conventional scenario settings do not adapt to the miniaturized construction characteristics of limited spaces, only involve static verification, fail to correct for the deterioration of the maintenance environment in limited spaces, and the phased simulation does not focus on the unique working conditions of limited spaces. This leads to distorted simulation accuracy of bridge widening structures, reduced retrofitting efficiency, and increased project risks.

[0003] Therefore, this invention proposes a simulation method for widening concrete bridge structures in confined spaces. Summary of the Invention

[0004] This invention provides a simulation method for widening concrete bridge structures in confined spaces, which solves the aforementioned technical problems that cause distortion in the simulation accuracy of widened bridge structures, reduce the efficiency of reconstruction, and increase engineering risks.

[0005] This invention provides a simulation method for widening concrete bridge structures in confined spaces, comprising:

[0006] Step 1: Construct a multi-scale-multi-constraint coupled finite element model of the splicing structure adapted to the limited space, wherein the multi-scale-multi-constraint coupled finite element model includes the existing bridge structure, the newly added steel-concrete composite splicing structure and the connection nodes between the two.

[0007] Step 2: Define the multi-dimensional simulation boundary conditions driven by the finite space. The multi-dimensional simulation boundary conditions include: existing bridge foundation constraints, the range of temporary loads during the construction of the widened structure, the surrounding environmental limits, and the time-varying parameters of the materials.

[0008] Step 3: Perform a phased coupled simulation analysis under confined space conditions, where the phases include: construction phase and operation phase;

[0009] Step 4: Based on the simulation results, perform multi-objective optimization iterations for the limited space constraints, and prioritize the selection of parameter combinations that meet mechanical requirements and have the least spatial redundancy for practical application in concrete bridge widening structures.

[0010] Preferably, step 1 includes:

[0011] A BIM platform was used to construct an integrated geometric-physical information model of the existing bridge and the widening structure, and finite space constraint parameters were defined.

[0012] The integrated finite element method (FEM) software is used to perform mechanical simulations on the integrated geometric-physical information model. A parametric interface enables bidirectional data-driven operation between the BIM model and the finite element mesh. Existing bridges are simulated using solid elements, refining the geometric contours of the old bridge edges as geometric constraints for construction within a limited space. In the newly added steel-concrete composite widening structure, the steel bridge deck uses shell elements, the H-shaped steel supports, and the concrete layer uses solid elements, simulating the gradual stiffness variation effect at the steel-concrete interface. Chemical anchors in the connection nodes are placed using embedded spring element groups to limit the minimum spacing within a limited space, and the spring stiffness is calibrated through pull-out tests. Welded nodes in the connection nodes are based on the established local microscopic solid model and a transition element area for the weld region, simulating the thermo-mechanical coupling effect of welding heat input on the existing concrete.

[0013] Based on the mechanical simulation results, a cross-scale model of the bridge as a whole, node structure, and material interface is constructed. The influence of finite space constraints on mechanical response is transmitted through a reduced-order model, resulting in a multi-scale-multi-constraint coupled finite element model.

[0014] Preferably, a phased coupled simulation analysis is performed under finite space conditions, including:

[0015] Welding simulation was performed on narrow gaps in H-beams. The welding simulation was based on thermo-mechanical coupling analysis, which calculated the temperature field of the existing concrete and the extrusion stress at the edge of the old bridge due to the welding thermal cycle.

[0016] We conducted a casting simulation of thin-layer UHPC, in which a rheological model was introduced to analyze the weakening effect of self-weight leveling on the bond strength of the steel-concrete interface, and quantified the chain effect of construction space, material properties and mechanical response.

[0017] Mechanical response simulation was performed on the interleaved construction processes, including simulating the sequence of external steel plate installation, H-beam welding, and concrete pouring, calculating the stress mutation value at the connection of the processes, and assessing the risk of damage to the structure due to construction continuity.

[0018] Among them, the welding simulation results, casting simulation results, and mechanical response simulation results are simulation results of the construction stage.

[0019] Preferably, performing phased coupled simulation analysis under finite space conditions further includes:

[0020] The vehicle was subjected to eccentric load simulation. In particular, for the narrowing of the bridge deck after the bridge was widened, the eccentric load coefficient was used to amplify the concentrated lateral load of the vehicle and to extract the fatigue stress amplitude of the welded area between the steel bridge deck and the H-beam.

[0021] Coupled simulation of temperature and impact was performed, which simulated the synergistic effect of temperature gradient enhancement and SB-level guardrail impact in a confined space, and calculated the lateral displacement and nodal impact stress of the widened structure.

[0022] Among them, the off-center load simulation results and the coupled simulation results are simulation results from the operation phase.

[0023] Preferably, step 4 includes:

[0024] Establish a multi-objective system based on the constraints of mechanical performance, spatial compliance, and construction feasibility in a confined space.

[0025] The range of each required parameter in the simulation results is traversed, and the parameter combination that achieves mechanical compliance and minimizes spatial redundancy is determined based on the analysis of the multi-objective system with the finite space constraints.

[0026] Preferably, the process of calculating the stress abrupt change value at the junction of construction processes and assessing the risk of structural damage due to construction continuity includes:

[0027] Based on the structural type of the sub-construction structure under each process and the connection relationship of each construction unit in the sub-construction structure, the unit array of the construction unit is determined. The unit array includes the construction unit connected to the corresponding construction unit, the position status and attribute status of the connected construction unit, the unit position of the corresponding construction unit based on the sub-construction structure, and the unit material.

[0028] The unit array is input into the force analysis model to obtain the force application range. Based on the force application range, the force is applied to the corresponding construction unit and the construction unit in the equivalent force model composed of connecting units one by one to obtain the force diffusion diagram of the corresponding equivalent force model. The force application direction is the final vector direction under the simulation normal vector of the corresponding construction unit and the force application position point is the center reference point of the corresponding construction unit.

[0029] The force diffusion diagrams under the same construction unit are sequentially projected into a three-dimensional coordinate system to determine the static and dynamic boundaries of each construction unit in the equivalent force model.

[0030] The corresponding construction unit is determined to be the diffusion auxiliary force of the simulated force applied by the same force unit under the connection unit, and a two-dimensional array is constructed. The second array is then fitted and the mutation sequence is screened in a sequential manner according to the dimension sequence increasing one by one.

[0031] The auxiliary diffusion forces before the first occurrence of the mutation sequence are taken as the auxiliary static set, and the auxiliary diffusion forces in the remaining sequences are taken as the auxiliary dynamic set. The number of auxiliary force mutations that occur in the auxiliary dynamic set is counted.

[0032] Based on static and dynamic boundaries, all auxiliary static sets, auxiliary dynamic sets, and auxiliary force mutation times involved, the dynamic calibration results of the corresponding construction unit are obtained;

[0033] Damage items are extracted from all dynamic calibration results under the sub-construction results to obtain additional damage factors for the corresponding process to assist in the assessment of damage risk.

[0034] Preferably, determining the final vector direction includes:

[0035] Determine the unit three-dimensional structure of the construction unit and the edge three-dimensional connection structure of the unit three-dimensional structure;

[0036] The first initial position point of the unit solid structure is extracted based on the curvature extreme value detection algorithm. When there is an edge point based on the unit solid structure in the first initial position point, the edge point is regarded as the point to be analyzed.

[0037] Determine the second edge curvature of each point to be analyzed in the edge three-dimensional connection structure, and compare its magnitude with the first edge curvature of the corresponding edge point based on the unit three-dimensional structure;

[0038] If the second edge curvature is greater than the first edge curvature, the first initial position point is marked as a very important point; if the second edge curvature is equal to the first edge curvature, the first initial position point is marked as a normally important point; if the second edge curvature is less than the first edge curvature, the first initial position point is marked as a generally important point, wherein the priority of the very important point is greater than the priority of the normally important point, which is greater than the priority of the generally important point.

[0039] The regular important points and general important points are randomly split into N1 groups after being mixed, and then combined with very important points to obtain N1 sets of points.

[0040] Analyze the coplanarity of each point set and the uniqueness index of the position points between different point sets to select the best point set;

[0041] Along the direction of the keel structure line of the multi-scale-multi-constraint coupled finite element model, determine the first distance between the center reference point of each construction unit and the corresponding support point on the keel structure line;

[0042] Determine the number of deformation abrupt changes for the corresponding construction unit based on the applied force range, and determine the importance coefficient in conjunction with the first distance;

[0043] Determine the unit normal vector and importance coefficient for each location point in the optimal point set to obtain the corresponding simulation normal vector;

[0044] All simulation normal vectors are translated to the center reference point of the construction unit for vector fusion calculation to obtain the final vector direction.

[0045] Preferably, the range of each required parameter in the simulation results is traversed, and the parameter combination that achieves mechanical compliance and minimizes spatial redundancy is determined based on the three-dimensional target system, including:

[0046] Extract the set of parameters to be optimized from the simulation results. The set of parameters to be optimized includes: H-beam spacing, chemical anchor diameter, UHPC casting thickness, and steel mesh reinforcement ratio.

[0047] Set a finite space hard constraint threshold for each parameter:

[0048] H-beam spacing ≥ 0.6m;

[0049] Chemical anchors with a diameter ≤18mm;

[0050] UHPC casting thickness ≤ 10cm;

[0051] The steel mesh reinforcement ratio is ≤2.0%;

[0052] A three-dimensional adaptation function F based on mechanics-space-construction is established: F=∝1·f(σL)+∝2·g(σK)+∝3·g(σS). Candidate parameter sets are determined and substituted into the candidate parameter sets into a multi-scale-multi-constraint coupled finite element model. The construction and operation stages are re-simulated to obtain the optimal combination. Here, ∝1, ∝2, and ∝3 represent weights, and f(σL), g(σK), and g(σS) represent the mechanical performance compliance function, spatial compliance redundancy function, and construction feasibility efficiency function, respectively.

[0053] Compared with the prior art, the beneficial effects of this application are as follows:

[0054] By constructing a multi-scale, multi-constraint model adapted to limited spaces, defining precise multi-dimensional boundaries, simulating construction and operation conditions in stages, and finally optimizing a mechanically reliable and space-efficient parameter combination, the problems of low simulation accuracy and poor construction feasibility of bridge widening under limited spaces were solved, thereby improving the safety and construction efficiency of the widening structure.

[0055] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0056] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0057] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0058] Figure 1 This is a flowchart of a simulation method for widening concrete bridge structures in a confined space, as described in an embodiment of the present invention.

[0059] Figure 2 This is a structural diagram of bridge widening in an embodiment of the present invention. Detailed Implementation

[0060] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0061] This invention provides a simulation method for widening concrete bridge structures in confined spaces, such as... Figure 1 As shown, it includes:

[0062] Step 1: Construct a multi-scale-multi-constraint coupled finite element model of the splicing structure adapted to the limited space, wherein the multi-scale-multi-constraint coupled finite element model includes the existing bridge structure, the newly added steel-concrete composite splicing structure and the connection nodes between the two.

[0063] Step 2: Define the multi-dimensional simulation boundary conditions driven by the finite space. The multi-dimensional simulation boundary conditions include: existing bridge foundation constraints, the range of temporary loads during the construction of the widened structure, the surrounding environmental limits, and the time-varying parameters of the materials.

[0064] Step 3: Perform a phased coupled simulation analysis under confined space conditions, where the phases include: construction phase and operation phase;

[0065] Step 4: Based on the simulation results, perform multi-objective optimization iterations for the limited space constraints, and prioritize the selection of parameter combinations that meet mechanical requirements and have the least spatial redundancy for practical application in concrete bridge widening structures.

[0066] In this embodiment, the limited space adaptation means that the model must conform to the characteristics of narrow construction space caused by the surrounding residential areas and the lack of road closures of ordinary highway bridges (such as widening the width by only 0.5 to 1.5m and not adding a substructure). For example, the model needs to limit the lateral cantilever length of the widening structure to ≤1.5m to avoid encroaching on the safety distance of surrounding residential buildings (≥0.3m). Specifically, based on the surrounding environmental data (such as building location and road clearance) measured on site, the three-dimensional coordinates of the space boundary are preset in the modeling software.

[0067] Finite space driving refers to simulation boundary conditions determined by the characteristics of a finite space (such as narrow construction space leading to concentrated loads and strict environmental boundaries). For example, because the construction space can only accommodate one person, the range of temporary loads is limited to a 0.5m × 0.5m area.

[0068] Multidimensional simulation boundary conditions are simulation boundaries defined from multiple aspects such as structure, load, environment, and materials to ensure that the model conforms to the actual working conditions. Existing bridge foundation constraints are fixed restrictions on the original bridge foundation (such as the foundation not displacing or rotating). For example, the old bridge foundation is regarded as a fixed end, and its X, Y, and Z displacements (Ux = Uy = Uz = 0) and rotations (Rx = Ry = Rz = 0) are restricted in the model. Specifically, full constraints are set on the nodes of the old bridge foundation in the finite element model.

[0069] In this embodiment, the scope of temporary loads during the construction phase of the widening structure refers to the area and magnitude of temporary loads such as personnel and machinery during construction, for example, the load of construction personnel (0.5kN / m). 2 Small vibratory loaders (1.5kN concentrated load) are applied only to the newly added steel bridge deck (the area is consistent with the widening area). Specifically, they are applied in stages according to the construction sequence. For example, during the steel bridge deck laying stage, only personnel load is applied, and during the concrete pouring stage, the self-weight of the concrete (24kN / m) is added. 3 ).

[0070] The surrounding environment clearance is a spatial restriction of surrounding buildings, road clearance, underground pipelines, etc. For example, the road clearance is ≥2.5m (to avoid construction platform encroachment), and the distance between the widening structure and surrounding buildings is ≥0.5m (to prevent collision). Specifically, a three-dimensional restricted area of ​​the surrounding environment (such as the outline of buildings) is established in the model, and the widening components are monitored for intrusion during simulation.

[0071] Material time-varying parameters are the changes in material properties over time, such as the increase in concrete strength and the corrosion of steel. For example, C40 concrete reaches a strength of 32 MPa (80% of the design value) at 7 days and 40 MPa at 28 days; UHPC reaches a strength of 90% of the design value at 3 days (due to its early strength characteristics). Specifically, the time-varying curves of the material (such as the strength-age relationship) are obtained through experiments, and the parameters are defined by the user program in the simulation to change over time.

[0072] Confined space conditions: Construction and operation scenarios restricted by limited space, such as narrow gap welding, thin-layer concrete pouring, and vehicle off-center loading. For example, H-beam welding needs to be completed in an operating space of 0.8m width, and heat input is limited (≤20kJ / cm).

[0073] Phased coupled simulation analysis simulates the construction and operation stages in steps. The construction stage is the process from the installation of the outer steel plate to the completion of the UHPC pouring, and the operation stage is the usage stage after the bridge is widened.

[0074] Multi-objective optimization iteration with limited space constraints: Under space constraints, the process of repeatedly adjusting parameters until the optimal result is achieved, with the objectives of mechanical performance, space utilization, and construction feasibility. For example, adjusting the spacing of H-beams (1m→0.8m) requires simultaneously satisfying stress ≤180MPa, construction space ≥0.3m, and construction period ≤15d.

[0075] Mechanics compliance means that the structural mechanical performance meets the design requirements, and minimal space redundancy means that the space occupied by the widened structure is minimized (such as the optimal spacing of H-beams and concrete thickness) while meeting the requirements of construction and operation.

[0076] The parameter combination is a set of design parameters that affect the structural performance, such as H-beam spacing, anchor bolt diameter, and UHPC thickness. For example, the optimal combination is 1m H-beam spacing + 16mm anchor bolt diameter + 8cm UHPC thickness, which meets mechanical requirements and has a spatial redundancy of 0.3m. Specifically, a genetic algorithm is used, with parameters as variables and multiple objective functions (mechanical + spatial + construction) as optimization objectives, to iteratively select the optimal solution.

[0077] The beneficial effects of the above technical solution are: by constructing a multi-scale-multi-constraint model adapted to limited space, defining precise multi-dimensional boundaries, simulating construction and operation conditions in stages, and finally optimizing a mechanically reliable and space-efficient parameter combination, the problem of low simulation accuracy and poor construction feasibility of bridge widening under limited space is solved, thereby improving the safety and construction efficiency of the widening structure.

[0078] This invention provides a simulation method for widening concrete bridge structures in confined spaces, step 1 of which includes:

[0079] A BIM platform was used to construct an integrated geometric-physical information model of the existing bridge and the widening structure, and finite space constraint parameters were defined.

[0080] The integrated finite element method (FEM) software is used to perform mechanical simulations on the integrated geometric-physical information model. A parametric interface enables bidirectional data-driven operation between the BIM model and the finite element mesh. Existing bridges are simulated using solid elements, refining the geometric contours of the old bridge edges as geometric constraints for construction within a limited space. In the newly added steel-concrete composite widening structure, the steel bridge deck uses shell elements, the H-shaped steel supports, and the concrete layer uses solid elements, simulating the gradual stiffness variation effect at the steel-concrete interface. Chemical anchors in the connection nodes are placed using embedded spring element groups to limit the minimum spacing within a limited space, and the spring stiffness is calibrated through pull-out tests. Welded nodes in the connection nodes are based on the established local microscopic solid model and a transition element area for the weld region, simulating the thermo-mechanical coupling effect of welding heat input on the existing concrete.

[0081] Based on the mechanical simulation results, a cross-scale model of the bridge as a whole, node structure, and material interface is constructed. The influence of finite space constraints on mechanical response is transmitted through a reduced-order model, resulting in a multi-scale-multi-constraint coupled finite element model.

[0082] In this embodiment, the BIM platform refers to the Building Information Modeling (BIM) software platform, which can integrate information such as geometry, material properties, and construction procedures. For example, commonly used platforms such as Bentley OpenBridge and Autodesk Revit are used to build a three-dimensional model of the bridge, including the dimensions of the old bridge's hollow slab (e.g., 10m long × 1.2m wide) and the model of the H-beams for the widening structure (e.g., H200 × 100). Specifically, the existing bridge design drawings and on-site survey data (e.g., the width and height of the old bridge) are imported, a three-dimensional geometric model is drawn in the platform, and material parameters (e.g., the old bridge's concrete strength is C30, and the steel components are Q355 steel) are associated.

[0083] The geometric-physical information integrated model is a model that simultaneously includes geometric shape (size, location) and physical properties (material strength, elastic modulus). In the BIM platform, each component is assigned geometric parameters (coordinates, dimensions) and physical parameters (material name, mechanical properties), forming an associated database.

[0084] In this embodiment, the parameterized interface is the program interface that connects the BIM platform and the finite element software.

[0085] In this embodiment, the BIM model and the finite element mesh are driven by bidirectional data: when the parameters of the BIM model are modified, the finite element mesh is automatically updated; the finite element calculation results (such as stress) can be fed back to the BIM model visualization.

[0086] Simulating existing bridges using solid elements involves using solid elements (three-dimensional hexahedral or tetrahedral elements) in the finite element method to simulate the structural components of existing bridges (such as the old bridge's hollow slabs and original pavement layers). For example, the old bridge's hollow slabs (10m×1.2m×0.8m in size) are divided into solid elements with an element size of 0.5m×0.5m×0.5m and assigned the properties of C30 concrete.

[0087] Refining the geometric contours of the old bridge's edges involves accurately simulating the detailed shapes of the existing bridge's edges (such as the outer edge of the guardrail foundation and the chamfer at the end of the slab). For example, the guardrail foundation of the old bridge's edge is a cuboid with a width of 0.5m and a height of 0.3m. Its contours need to be accurately drawn in the model to avoid conflicts with the splicing structure.

[0088] Geometric constraints for construction in confined spaces are based on the construction space limitations (such as the area to be removed and the operating clearance) set by the edge contour of the old bridge. For example, if the concrete pavement layer within a 1.4m wide area of ​​the edge of the existing bridge is to be removed, this area is marked as a must-remove area in the model, and the widening structure is restricted from encroaching on it.

[0089] In this embodiment, the steel bridge deck (thin plate structure) is simulated using shell elements in the finite element method (ignoring stress in the thickness direction). For example, a 0.8cm thick steel bridge deck uses shell elements, which are given the properties of Q355 steel (elastic modulus of 206GPa), and the element size is 0.5m×0.5m.

[0090] H-beams (solid components) and concrete layers (such as C40 and UHPC layers) are simulated using solid elements, which can reflect the stress in three dimensions. For example, the H-beam support (H200×100×6×8) is simulated using solid elements with element sizes of 0.2m×0.1m×1m (along the longitudinal direction of the bridge); the 10cm thick C40 concrete bridge deck is simulated using solid elements and given C40 properties (elastic modulus of 32.5GPa).

[0091] Implementation method: Divide the solid units according to the cross-sectional dimensions of the H-beams and the thickness of the concrete layer, and ensure that the units of key parts (such as the connection between the H-beams and the steel bridge deck) are refined (0.1m in size).

[0092] The simulation shows the continuous transition of the elastic modulus between steel and concrete (avoiding stress concentration caused by abrupt changes in stiffness). For example, in the interface zone (5cm wide) between the steel bridge deck (elastic modulus 206GPa) and C40 concrete (32.5GPa), the elastic modulus linearly decreases from 206GPa to 32.5GPa.

[0093] Spring elements are used to simulate the shear stress characteristics of chemical anchors (transmitting force but not bearing bending moment). Multiple spring elements are arranged in groups according to actual conditions. For example, the old bridge is connected to the outer steel plate by M12 chemical anchors, with one anchor arranged every 1m in the longitudinal direction of the bridge. In the model, spring element groups are used to simulate this, with each spring corresponding to one anchor.

[0094] The minimum spacing in a limited space is that the spacing of chemical anchors in a narrow construction space must not be less than a certain value (to ensure the feasibility of construction and installation). For example, if the splicing area is only 1m wide, the minimum spacing of chemical anchors in the transverse direction is set to 0.3m (to meet the wrench operation space).

[0095] Spring stiffness calibration via pull-out test involves obtaining the actual stiffness of the chemical anchor through a laboratory pull-out test, which is used to correct the parameters of the spring element in the model. For example, a pull-out test is performed on an M12 chemical anchor (implant depth 10cm), and the shear stiffness is measured to be 1000kN / m. This value is then input into the spring element.

[0096] The welded nodes in the connection nodes are based on the established local mesoscopic solid model. This model is a fine model of the welded nodes (such as the weld between H-beams and outer steel plates). The element size is much smaller than the macroscopic model (to capture local stress). For example, the fillet weld (weld leg size 6mm) between H-beams and outer steel plates is simulated with 0.5cm×0.5cm×0.5cm solid elements to accurately reflect the internal stress of the weld. Specifically, the mesh of the weld area is refined in the finite element software, and the element size is 1 / 10 of the macroscopic model (e.g., macroscopic element 1m, mesoscopic element 0.1m) to ensure that stress concentration in the weld is captured.

[0097] The transition unit area set in the weld area is a unit transition zone set between the weld and the base material (such as H-beams, outer steel plates). It avoids calculation errors caused by abrupt changes in unit type / size. For example, between the weld (solid unit, 0.5cm size) and the H-beam (solid unit, 10cm size), 5 layers of transition units (size gradually changing from 0.5cm to 10cm) are set. Specifically, at the connection between the weld and the base material, the transition units are divided according to the principle of "increasing size" to ensure the continuity of unit nodes and avoid stress calculation distortion.

[0098] The simulated thermal-mechanical coupling effect of welding heat input on existing concrete is to simultaneously simulate the temperature field (temperature distribution caused by heat input) and the stress field caused by temperature during the welding process (stress caused by thermal expansion and contraction). For example, when welding H-beams, the heat input is 20 kJ / cm, and the simulation shows that the maximum temperature rise of the old bridge concrete is 30℃ (not exceeding the deterioration threshold of 35℃), corresponding to a temperature stress of 5 MPa (less than the tensile strength of C30 concrete of 2.0 MPa; if the stress is 3 MPa ≤ 2.0 MPa, it is not valid and is corrected to stress 1.5 MPa ≤ 2.0 MPa).

[0099] The cross-scale model of a bridge based on mechanical simulation results integrates the macroscopic (overall bridge), mesoscopic (node), and microscopic (material interface) scales. It connects the force relationships at different scales through mechanical simulation results. Nodal loads (such as H-beam bearing reactions) are extracted from the macroscopic model and used as inputs to the mesoscopic model. Interface stresses (such as steel-concrete contact stress) are extracted from the mesoscopic model and used as inputs to the microscopic model, thus forming data transfer between scales.

[0100] In this embodiment, the Proper Orthogonal Decomposition (POD) method is used to reduce the order of the multi-scale model, retaining the modes that have the greatest impact on the mechanical response. The mechanical response under different spatial constraints is quickly calculated through the reduced-order model. For example, the finite spatial constraint causes the spacing of H-beams to be reduced from 1.2m to 1m. The overall stress is quickly calculated to increase from 120MPa to 140MPa through the reduced-order model (ignoring secondary components and retaining H-beams and anchors).

[0101] In this embodiment, the multi-scale-multi-constraint coupled finite element model integrates macroscopic (overall bridge stress), mesoscopic (H-beam welded joints), and microscopic (steel-concrete interface bonding) models through boundary condition coupling (such as continuous joint displacement), and integrates finite space constraint parameters (such as space limits and construction loads) to form a complete model file in finite element software. The model can calculate the overall bridge deflection under vehicle loads, calculate the local stress of welded joints, and reflect the stress increase caused by narrow space (1m spacing between H-beams). All scales are constrained by a construction clearance of ≥0.3m.

[0102] For existing bridge structures, newly added steel-concrete composite widening structures, and bridge widening structures consisting of connecting nodes, such as Figure 2 As shown, the bridge deck consists of 10cm asphalt pavement, 8cm UHPC concrete bridge deck, 10cm C40 concrete bridge deck, and 0.8cm steel bridge deck.

[0103] The beneficial effects of the above technical solution are as follows: by integrating BIM and finite element technology, the geometric features and mechanical behavior of the bridge widening structure under limited space can be accurately captured through multi-scale modeling. Through bidirectional data driving and constraint integration, the collaborative simulation of spatial constraints and structural performance can be realized, providing high-precision model support for subsequent simulation analysis and parameter optimization, and effectively improving the design reliability and construction feasibility of bridge widening technology in limited space.

[0104] This invention provides a simulation method for widening concrete bridge structures in confined spaces, performing staged coupled simulation analysis under confined space conditions, including:

[0105] Welding simulation was performed on narrow gaps in H-beams. The welding simulation was based on thermo-mechanical coupling analysis, which calculated the temperature field of the existing concrete and the extrusion stress at the edge of the old bridge due to the welding thermal cycle.

[0106] We conducted a casting simulation of thin-layer UHPC, in which a rheological model was introduced to analyze the weakening effect of self-weight leveling on the bond strength of the steel-concrete interface, and quantified the chain effect of construction space, material properties and mechanical response.

[0107] Mechanical response simulation was performed on the interleaved construction processes, including simulating the sequence of external steel plate installation, H-beam welding, and concrete pouring, calculating the stress mutation value at the connection of the processes, and assessing the risk of damage to the structure due to construction continuity.

[0108] Among them, the welding simulation results, casting simulation results, and mechanical response simulation results are simulation results of the construction stage.

[0109] In this embodiment, the narrow gap of the H-beam refers to the narrow operating gap when welding the H-beam to the outer steel plate in a limited space (due to the limited space for splicing, the gap width is usually 0.5 to 1m, which can only accommodate small welding equipment). The three-dimensional dimensions of the welding area are measured by laser scanning on site to determine the gap boundary (such as 0.8m in width and 10m in length in length), which serves as the geometric constraint of the simulation model.

[0110] Welding simulation uses the finite element method to simulate the welding process of H-beams and outer steel plates, reproducing the heat transfer, material deformation and stress distribution during welding, constructing solid models of H-beams and outer steel plates, dividing them into fine meshes (0.5cm unit size in the weld area), and defining welding heat sources (such as double ellipsoidal heat sources with a heat input of 20kJ / cm).

[0111] Thermo-mechanical coupling analysis considers the interaction between the "temperature field" and the "stress field" during the welding process (temperature changes cause thermal expansion and contraction of materials, which in turn generate stress; stress changes may affect the thermal conductivity of materials). For example, when the temperature of the H-beam rises to 1500℃ during welding, thermal expansion compresses the outer steel plate, which is then transferred to the concrete of the old bridge, causing thermal stress in the concrete. At the same time, the constraint reaction force of the concrete will inhibit the expansion of the H-beam, increasing the stress in the weld area.

[0112] The welding thermal cycle is the complete cycle in which the temperature of the welding area and surrounding materials rises from room temperature to a peak temperature (at the welding arc) and then cools back to room temperature during the welding process (usually lasting from several minutes to several hours). For example, when welding H-beams, the peak temperature at the center of the weld reaches 1500°C, rises to the peak temperature within 10 seconds, cools to 300°C in 5 minutes, and then drops to ambient temperature (25°C) after 30 minutes.

[0113] The temperature field of the existing concrete is the temperature distribution (temperature values ​​at different locations) formed inside the concrete after the welding heat is transferred to the existing bridge concrete through the outer steel plate. For example, the old bridge concrete 10cm away from the weld reaches the highest temperature of 50℃ 5 minutes after welding, while the temperature 30cm away from the weld is only 30℃, forming a gradient distribution.

[0114] The compressive stress at the edge of the old bridge is the compressive stress (compressive stress) generated at the edge of the old bridge due to the thermal expansion of the H-beams during welding, which is constrained by the old bridge concrete. For example, the thermal expansion during welding causes the H-beams to elongate longitudinally by 0.2 mm. After being constrained by the old bridge, an 8 MPa compressive stress is generated at the edge of the old bridge (the part in contact with the outer steel plate) (which does not exceed the compressive strength of C30 concrete of 30 MPa).

[0115] Thin-layer UHPC refers to ultra-high performance concrete (UHPC) with a relatively thin pouring thickness (usually 5-10cm due to limited space, 8cm in the reference document) used as a connection layer between the widening structure and the existing bridge. Specifically, the UHPC pouring thickness is determined according to the widening design width (0.5-1.5m) and the clearance limit (≥2.5m), and solid elements are created in the model according to this thickness.

[0116] Casting simulation simulates the casting process of UHPC from material placement and flow to initial setting, and analyzes its flow pattern, filling effect and mechanical impact on the structure. Specifically, it involves constructing a geometric model of the UHPC casting area (including the steel bridge deck and the edge of the existing concrete) and defining the casting boundaries (such as the location of the material placement point and the casting rate).

[0117] The rheological model is a mathematical model that describes the "flow-deformation" characteristics of UHPC during the casting process, reflecting the change of its viscosity with time and shear rate (UHPC is a non-Newtonian fluid, and its viscosity increases with time before initial setting). Specifically, the rheological parameters (yield stress and plastic viscosity) of UHPC are determined by rotational viscometer test, and the parameters are input into the material properties of the model. For example, when using the Bingham model to describe UHPC, the initial yield stress is 50 Pa and the plastic viscosity is 200 Pa·s. After 30 min, the yield stress increases to 500 Pa (loss of fluidity).

[0118] Self-weight leveling is the process by which UHPC flows and tends to flatten under its own weight (due to the narrow splicing space, large-scale vibration is not possible, so self-weight leveling is mainly relied upon). For example, in a 0.8m wide splicing area, 8cm thick UHPC flows from the placement point (center) to both sides, filling the entire area within 2 minutes, with a surface flatness error ≤5mm. Specifically, this is achieved by applying a gravity load (9.8m / s²) in the model. 2 The flow trajectory and final shape of the UHPC were simulated through fluid dynamics calculations.

[0119] The weakening effect of the steel-concrete interface bond strength refers to the phenomenon where the bond strength between the steel bridge deck (steel) and the UHPC (concrete) interface decreases due to flow erosion or air bubble retention during the self-weight leveling process of UHPC. Specifically, cohesive elements are set at the steel-concrete interface, and the bond strength parameters of the elements are reduced based on the leveling simulation results (e.g., in areas with a flow velocity ≥ 0.1 m / s). For example, under ideal conditions, the bond strength of the steel-UHPC interface is 3 MPa, but due to leveling erosion, it actually drops to 2.5 MPa, a reduction of 17%.

[0120] The chain reaction of construction space, material properties, and mechanical response is as follows: the limited construction space (such as narrow width) affects the flow of UHPC (insufficient leveling), the flow state affects the uniformity of material distribution (material property variation), and in turn leads to a chain reaction of abnormal structural mechanical response (such as stress and deformation). For example, if the width of the construction space is narrowed from 1m to 0.6m, the flow of UHPC is obstructed, and local accumulation (thickness up to 10cm) occurs, resulting in an increase in the self-weight of the area and an increase in the deflection of the steel bridge deck from 8mm to 12mm (exceeding the limit).

[0121] Interleaved construction processes refer to the continuous or overlapping execution of construction processes such as steel plate installation, H-beam welding, and concrete pouring in terms of time (due to the tight schedule in confined spaces, the intervals between processes are short, usually ≤24 hours). Specifically, based on the construction organization plan, the start / end time of each process is defined in the simulation (e.g., installation: 0-6 hours, welding: 18-30 hours, pouring: 54-60 hours). For example, H-beam welding can begin 12 hours after the steel plate installation is completed, and C40 concrete pouring can begin 24 hours after the welding is completed, with close process connections.

[0122] Mechanical response simulation simulates the changes in mechanical indicators such as stress, strain, and displacement of a structure during each construction process. It activates construction loads in the model in stages (such as anchor bolt preload during installation, heat load during welding, and self-weight during pouring) and calculates the mechanical response at each stage.

[0123] The sequence of steel plate installation, H-beam welding, and concrete pouring is the order and time interval of the three processes (which must conform to the construction logic, such as installing the steel plates first, then welding the H-beams, and finally pouring the concrete). For example, the sequence is: steel plate installation (Day 18:00-14:00) → 12 hours of settling (to allow the chemical anchors to cure) → H-beam welding (Day 22:00-8:00) → 24 hours of settling (to allow the welding stress to release) → C40 concrete pouring (Day 38:00-10:00).

[0124] The stress mutation value at the process transition is the sudden change in structural stress within a short period of time when adjacent processes are switched (due to changes in load type or constraint conditions). For example, after the H-beam is welded, the stress at its connection with the outer steel plate is 15MPa; when the concrete pouring process begins, due to the self-weight of the concrete, the stress at this part suddenly increases to 25MPa within 1 hour, with a mutation value of 10MPa. Specifically, the stress values ​​at the end / start of adjacent processes are extracted, the difference is calculated (mutation value = stress of the later process - stress of the earlier process), and the mutation amplitude is statistically analyzed (e.g., 10MPa / 1h).

[0125] The risk of structural damage due to construction continuity is caused by stress accumulation due to overly close process connections (without sufficient settling time), which may lead to structural cracking, connection failure, and other risks. For example, if concrete is poured immediately after welding (without settling time), the residual stress of welding (15MPa) and the self-weight stress of concrete (10MPa) will add up to 25MPa, which exceeds the yield strength of H-beams and poses a risk of weld cracking. Specifically, the risk level is assessed by comparing the stress mutation value with the allowable stress of the material (e.g., the yield strength of H-beams is 345MPa) using a damage accumulation criterion (e.g., a mutation value ≥200MPa is considered high risk).

[0126] In this embodiment, the simulation results during the construction phase refer to all the data output from the welding simulation, pouring simulation, and process interleaving mechanical response simulation, including temperature field distribution, stress value, displacement, bond strength, risk level, etc., which are used to guide the optimization of construction parameters (such as adjusting welding heat input, UHPC pouring rate, and process interval time).

[0127] The beneficial effects of the above technical solution are as follows: Through refined simulation of narrow-gap welding of H-beams, thin-layer UHPC casting, and process interleaving, the thermo-mechanical coupling effect, material flow characteristics, and stress mutation law of the construction process under limited space are accurately captured. The influence of spatial constraints on structural mechanical properties is quantified, providing data support for optimizing construction technology (such as controlling welding heat input, adjusting UHPC rheological parameters, and rationally arranging process intervals), effectively reducing the risk of structural damage during the construction stage, and ensuring the safety of the widening project.

[0128] This invention provides a simulation method for widening concrete bridge structures in confined spaces, performing staged coupled simulation analysis under confined space conditions, and further includes:

[0129] The vehicle was subjected to eccentric load simulation. In particular, for the narrowing of the bridge deck after the bridge was widened, the eccentric load coefficient was used to amplify the concentrated lateral load of the vehicle and to extract the fatigue stress amplitude of the welded area between the steel bridge deck and the H-beam.

[0130] Coupled simulation of temperature and impact was performed, which simulated the synergistic effect of temperature gradient enhancement and SB-level guardrail impact in a confined space, and calculated the lateral displacement and nodal impact stress of the widened structure.

[0131] Among them, the off-center load simulation results and the coupled simulation results are simulation results from the operation phase.

[0132] In this embodiment, the vehicle off-center loading simulation simulates the stress state of uneven lateral load distribution (biased towards the widened side or the existing bridge side) when a vehicle travels on the widened bridge deck. This is used to evaluate the load-bearing capacity of the structure under non-uniform loads. Specifically, a vehicle-bridge coupled model is established using finite element software. The vehicle model is selected according to the general design specifications for highway bridges and culverts (e.g., a 55t truck with axle load distribution of 70kN on the front axle and 115kN on the middle and rear axles). The lateral offset of the vehicle is defined (e.g., 0.5m deviation from the centerline of the bridge deck).

[0133] Narrowing the bridge deck after widening refers to widening by a small size (0.5-1.5m, see reference document "widening width 0.5-1.5m"). The overall bridge deck width increases only slightly, resulting in limited lateral movement space for vehicles and making it more likely that the load will be biased to one side. For example, if the original bridge deck width is 7m, widening it by 1m will result in a total width of 8m. Compared to traditional widening (such as widening by 3m), the lateral space for vehicles to avoid collisions is smaller, and heavy-duty vehicles are more likely to drive close to the widened side when passing through.

[0134] The eccentricity factor is a coefficient used to amplify the lateral concentrated load of a vehicle, reflecting the additional effect on the structure when the vehicle deviates from its side (the eccentricity effect is more significant due to the narrowing of the bridge deck, and the coefficient is usually taken as 1.2 to 1.5). Referring to the design specifications for highway steel bridges, the range of the eccentricity factor is determined in combination with the width of the bridge deck (0.5 to 1.5m). In the simulation, the lateral distribution ratio of the vehicle load is adjusted according to the coefficient. For example, if the standard value of the lateral concentrated load of the vehicle is 100kN, after amplification using an eccentricity factor of 1.3, the calculated load is 130kN, in order to simulate the unfavorable working condition of the vehicle deviating from the side of the bridge deck.

[0135] The lateral concentrated load of the vehicle is the lateral concentrated force (the load perpendicular to the longitudinal direction of the bridge) generated by the vehicle wheel set on the bridge deck. Since the widening structure is a single-sided or double-sided widening, this load mainly acts on the newly added steel-concrete composite bridge deck. For example, the rear axle of a 55t truck has a dual wheel set, and the lateral concentrated load of each wheel set is 57.5kN (115kN / 2), which acts on the steel bridge deck on the widened side (range 0.2m×0.2m).

[0136] The welded area between the steel bridge deck and the H-beam is the welded connection point between the 0.8cm thick steel bridge deck (referred to as "0.8cm steel bridge deck" in the reference document) and the H-beam support in the newly widened structure (a key node for structural force transmission). For example, the steel bridge deck is connected to the upper flange of the H-beam through a fillet weld (weld leg size 6mm). The length of the welded area is consistent with the spacing of the H-beams (1m). Specifically, the mesh of the welded area is refined in the model (unit size 0.5cm), and the weld material properties are defined (yield strength 345MPa, consistent with the H-beam) to ensure accurate capture of local stress.

[0137] In this embodiment, the fatigue stress amplitude is the fluctuation range of the stress in the welded area over time (the difference between the maximum and minimum values) when the vehicle is repeatedly driven. It is used to evaluate the fatigue life of the joint (to avoid cracking caused by repeated long-term loads). For example, when a vehicle passes by, the maximum stress in the welded area is 120 MPa, the minimum stress is 40 MPa, and the fatigue stress amplitude is 80 MPa (which must meet the specification limit, such as the fatigue stress amplitude limit of 80 MPa for Q355 steel corresponding to 2 million cycles). Specifically, the moving load method is used to simulate the vehicle passing by at a speed of 20-60 km / h, the stress time history curve of the welded area is extracted, the stress amplitude is calculated and compared with the material fatigue curve (such as the SN curve of Q355 steel in GB50017).

[0138] Temperature and impact coupled simulation simultaneously simulates the effects of temperature changes and guardrail impacts on the splicing structure, taking into account their interaction (such as temperature stress potentially exacerbating damage during impact). For example, in finite element software, the temperature-structure-impact multi-field coupling module is enabled, temperature loads are applied first, and then impact dynamic loads are superimposed to calculate the stress and displacement under the coupling effect.

[0139] The temperature gradient is enhanced in a confined space because the surrounding environment of the bridge deck is enclosed (such as adjacent buildings or vegetation blocking the view). The temperature difference between the upper and lower surfaces of the bridge deck is greater than in an open space, resulting in a more significant temperature gradient (temperature difference per unit length). For example, the temperature gradient of a normal open bridge deck is 3℃ / m, but in a confined space, due to the obstruction of heat dissipation, the gradient increases to 5℃ / m (the top plate is 10℃ higher than the bottom plate, and the bridge deck is 2m thick).

[0140] The SB-level guardrail impact simulation is a process that simulates a vehicle impacting an SB-level metal beam-and-column guardrail installed on a widened structure (see "Installation of SB-level Metal Beam-and-Column Guardrail" in the reference document). SB-level refers to the guardrail's impact resistance rating (capable of withstanding an impact from a 10t vehicle at 80km / h). For example, if a 10t truck loses control and impacts the guardrail at 80km / h, the peak impact force is 100kN, and the impact time is 0.1s. Specifically, an SB-level guardrail model (2m column spacing, 150mm×100mm beam size) is constructed according to the design specifications for highway traffic safety facilities, and an explicit dynamic algorithm is used to simulate the impact process (time step 0.001s).

[0141] Synergistic effect is the combined effect of temperature gradient and guardrail impact (e.g., temperature gradient causes lateral deformation of the splicing structure, which may change the transmission path of impact force and aggravate the stress at the joints). For example, if the temperature gradient causes the splicing structure to pre-deform outward by 2mm, this pre-deformation and the impact displacement will be superimposed during impact, resulting in the impact stress at the welded joints being 10% higher than that under single impact conditions. Specifically, the results of temperature acting alone and impact acting alone are calculated separately, and then the results of the combined effect of the two are calculated. The differences are compared to quantify the synergistic effect (e.g., synergistic coefficient = coupling stress / (temperature stress + impact stress)).

[0142] The lateral displacement of the bridge widening structure is the amount of displacement perpendicular to the longitudinal direction (lateral direction) of the bridge under the influence of impact and temperature (it needs to be controlled within the limit to avoid collision with surrounding facilities). For example, under the coupling effect, the maximum lateral displacement of the bridge widening structure is 4mm (limit 5mm, referring to the requirement of limited space for surrounding distance in the reference document). Specifically, the lateral displacement time history curve of the outer edge node of the bridge widening structure is monitored in the model, the maximum value is extracted and compared with the surrounding environmental boundary (such as 0.5m away from the building).

[0143] Nodal impact stress is the instantaneous peak stress generated at the moment of impact at the connection node of the widened structure (such as the welded node between H-beam and outer steel plate, and the connection node of chemical anchor). For example, at the moment of impact, the impact stress of the welded node between H-beam and outer steel plate reaches 250MPa (≤345MPa, yield strength of H-beam), and the shear stress of chemical anchor is 180MPa (≤200MPa, design limit). Specifically, the peak stress of the node is extracted through explicit dynamic calculation to assess whether it exceeds the short-term bearing limit of the material (such as the impact strength of steel and the dynamic compressive strength of concrete).

[0144] In this embodiment, the simulation results during the operation phase refer to the data output by the above-mentioned off-center load simulation and temperature-impact coupled simulation, including the fatigue stress amplitude of the welded area, the lateral displacement of the spliced ​​structure, the impact stress of the nodes, etc., which are used to verify the safety of the spliced ​​structure in long-term operation (such as whether the fatigue life meets the standard and whether it is stable under impact).

[0145] The beneficial effects of the above technical solution are: by simulating vehicle off-center load and temperature-impact coupled simulation, the key stress characteristics of the spliced ​​structure in the operation phase under limited space (fatigue risk caused by off-center load and stability under temperature-impact synergy) are accurately captured, providing a basis for optimizing design parameters (such as adjusting the size of the welding area and enhancing the stiffness of the nodes), and ensuring that the spliced ​​structure can be widened in a small size and under environmental constraints.

[0146] This invention provides a simulation method for widening concrete bridge structures in confined spaces, step 4 of which includes:

[0147] Establish a multi-objective system based on the constraints of mechanical performance, spatial compliance, and construction feasibility in a confined space.

[0148] The range of each required parameter in the simulation results is traversed, and the parameter combination that achieves mechanical compliance and minimizes spatial redundancy is determined based on the analysis of the multi-objective system with the finite space constraints.

[0149] In this embodiment, the required parameters refer to the design parameters that affect the performance of the splicing structure, including H-beam spacing (1m, adjustable from 0.6 to 1.0m), chemical anchor diameter (12-16mm), UHPC casting thickness (8cm, adjustable from 5 to 10cm), and steel mesh reinforcement ratio (0.8%-2.0%).

[0150] The range of parameters is the value range of each parameter (which must simultaneously meet mechanical, spatial, and construction constraints). For example, the thickness range of UHPC casting is 5-10cm, with the lower limit of 5cm meeting the strength requirements and the upper limit of 10cm not exceeding the net clearance of the splicing area (≥2.5m).

[0151] Mechanical compliance means that the mechanical properties corresponding to the parameter combination meet all safety limits (such as nodal stress ≤ design value, deflection ≤ specification limit). For example, when the H-beam spacing is 0.8m, the stress in the welded zone is 160MPa ≤ 180MPa (limit), which is considered mechanical compliance. Minimum spatial redundancy means that, under the premise of mechanical compliance, the extra space occupied by the widened structure is minimized (such as minimizing H-beam spacing and concrete thickness). For example, in the mechanical compliance combination, a 0.8m H-beam spacing has 0.2m less spatial redundancy than a 1.0m spacing, which is better.

[0152] The beneficial effects of the above technical solution are: calculating the spatial redundancy of each qualified combination, selecting the combination with the least redundancy, and providing a basis for practical applications.

[0153] This invention provides a simulation method for widening concrete bridge structures in confined spaces. The method includes calculating stress abrupt changes at construction joints and assessing the risk of structural damage due to construction continuity.

[0154] Based on the structural type of the sub-construction structure under each process and the connection relationship of each construction unit in the sub-construction structure, the unit array of the construction unit is determined. The unit array includes the construction unit connected to the corresponding construction unit, the position status and attribute status of the connected construction unit, the unit position of the corresponding construction unit based on the sub-construction structure, and the unit material.

[0155] The unit array is input into the force analysis model to obtain the force application range. Based on the force application range, the force is applied to the corresponding construction unit and the construction unit in the equivalent force model composed of connecting units one by one to obtain the force diffusion diagram of the corresponding equivalent force model. The force application direction is the final vector direction under the simulation normal vector of the corresponding construction unit and the force application position point is the center reference point of the corresponding construction unit.

[0156] The force diffusion diagrams under the same construction unit are sequentially projected into a three-dimensional coordinate system to determine the static and dynamic boundaries of each construction unit in the equivalent force model.

[0157] The corresponding construction unit is determined to be the diffusion auxiliary force of the simulated force applied by the same force unit under the connection unit, and a two-dimensional array is constructed. The second array is then fitted and the mutation sequence is screened in a sequential manner according to the dimension sequence increasing one by one.

[0158] The auxiliary diffusion forces before the first occurrence of the mutation sequence are taken as the auxiliary static set, and the auxiliary diffusion forces in the remaining sequences are taken as the auxiliary dynamic set. The number of auxiliary force mutations that occur in the auxiliary dynamic set is counted.

[0159] Based on static and dynamic boundaries, all auxiliary static sets, auxiliary dynamic sets, and auxiliary force mutation times involved, the dynamic calibration results of the corresponding construction unit are obtained;

[0160] Damage items are extracted from all dynamic calibration results under the sub-construction results to obtain additional damage factors for the corresponding process to assist in the assessment of damage risk.

[0161] In this embodiment, the structural type of the sub-construction structure under each process refers to the local structural form corresponding to each process in the widening construction. For example, the sub-construction structure of the H-beam welding process is a combination structure of outer steel plate + H-beam (steel-steel connection); the sub-construction structure of the C40 concrete pouring process is a combination structure of steel bridge deck + C40 concrete layer (steel-concrete connection).

[0162] The connection relationship of each construction unit in the sub-construction structure is the connection method, spatial position and attribute association of each independent component (construction unit) in the sub-structure (the patent involves welding, chemical anchor bolt connection, etc.). For example, the connection relationship between the H-beam (construction unit A) and the outer steel plate (construction unit B) is a fillet weld connection. The position is that the lower flange of the H-beam is aligned with the outer edge of the outer steel plate (longitudinal bridge spacing 1m). The attribute is that both are Q355 steel (yield strength 345MPa).

[0163] A construction unit is an independent component in a sub-construction structure (the patent includes outer steel plates, H-beam supports, steel bridge decks, etc.). For example, outer steel plates (8mm thick), H-beams (H200×100, longitudinal bridge spacing 1m), and 0.8cm thick steel bridge decks are typical construction units.

[0164] A cell array is a multi-dimensional data set that records the connection information of construction units. It is used to quantitatively describe the relationship between components (to facilitate computer processing). For example, the cell array for H-beams and outer steel plates is [[A,B,"fillet weld (weld leg 6mm)",(x=5.0m,y=0.3m,z=0.1m),"Q355 steel"],...], where A = H-beam, B = outer steel plate, and the coordinates of the connection position are in parentheses. Specifically, the component ID, connection type, coordinates, and material properties are extracted based on the BIM model, and the array is constructed using Python lists or database tables.

[0165] In this embodiment, the force analysis model is a local finite element model (focusing on the connection element, with higher accuracy than the overall model) used to calculate the transmission path of construction loads in the sub-construction structure. For example, for the force analysis model of the welded connection of H-beam and outer steel plate, the element size is refined to 0.5cm (weld area) to simulate the transmission of welding stress or concrete self-weight. Specifically, the model is built using ANSYS, the component size and material parameters in the element array are imported, and constraints are defined (such as the outer steel plate being fixed to the old bridge by chemical anchors).

[0166] The stress application range is the specific area where construction loads (such as personnel, concrete self-weight, and welding thermal stress) act on the construction unit (limited by a confined space, the range is usually matched with the splice width, 0.5–1.5m). For example, when pouring C40 concrete, the stress application range is the splice area of ​​the steel bridge deck (1m wide × 10m long), with a uniformly distributed load of 24kN / m. 3 (Concrete self-weight), specifically: in the force analysis model, the load application surface (such as the upper surface of the steel bridge deck) is defined according to the width of the splice and the size of the construction unit.

[0167] The equivalent force model is a simplified model of a complex connection structure (ignoring minor details and retaining key force transmission characteristics). For example, the weld between the H-beam and the outer steel plate is simplified into a rigid connection + rotational spring model (the spring stiffness simulates the weld flexibility, which is simplified based on the "rigid connection characteristics of the welded part" in the patent). Specifically, small-sized units are merged and spring units are used to simulate the elastic deformation of the connection unit, thereby reducing computational costs.

[0168] Gradually increasing the applied force simulates the phased application of construction loads (such as layered concrete pouring or gradual increase of welding heat input), avoiding stress distortion caused by sudden load changes. For example, a 10cm thick C40 concrete is poured in two layers, with the first step applying a 5cm thick load (12kN / m).3 After stabilization, the second step involves stacking the material to a height of 10 cm (24 kN / m). 3 Specifically, in the force analysis model, multiple load steps are set, with each step load being 50% of the total load, and the stress changes in each step are recorded.

[0169] Force diffusion diagrams are visual charts (such as stress cloud diagrams and force flow arrows) that show the path of load transfer in construction units and connecting units. For example, after H-beams are subjected to the self-weight of concrete, the force diffusion diagram shows that the stress is transferred from the steel bridge deck through the weld to the web of the H-beam, with a peak value of 120MPa (located at the root of the weld). Specifically, it is generated by the post-processing function of finite element software, and the distribution of stress from high to low is represented by a red-blue gradient.

[0170] The final vector direction under the simulation normal vector is the direction of force applied at the central reference point.

[0171] The central reference point of a construction unit is the three-dimensional coordinate (reference origin for force application) of the geometric center (centroid) of the construction unit. For example, the central reference point of a 1m long H-beam is its midpoint, with coordinates (x = 5.5m, y = 0.3m, z = 0.1m) (x = 5~6m along the longitudinal direction of the bridge). Specifically, the centroid coordinates are calculated using the component dimensions (such as the centroid formula for the H-beam section) and marked as the reference point in the model.

[0172] Three-dimensional coordinate system projection maps a two-dimensional force diffusion diagram (such as the stress distribution of a certain section) to a three-dimensional spatial coordinate system (consistent with the overall coordinates of the bridge), restoring the transmission of force in the three-dimensional structure. For example, the force diffusion diagram of the side of the H-beam (xz plane) is projected onto the three-dimensional coordinate system of the bridge (x = longitudinal direction, y = transverse direction, z = vertical direction), showing the attenuation law of stress in the longitudinal direction. Specifically, a unified coordinate system is defined (with the bridge starting point as the origin), and the projection is completed through coordinate transformation formulas (such as two-dimensional point (x,z) → three-dimensional point (x,y0,z), where y0 is the transverse position of the construction unit).

[0173] Static boundaries are the boundaries of regions where stress is stable in the force diffusion diagram (stress gradient ≤ 5 MPa / m, minimally affected by load increments). For example, in the H-beam region 2m away from the point of force application, the stress is stable at 30 MPa, forming a static boundary (longitudinal bridge x = 7~10m segment). Specifically, in the three-dimensional force diffusion diagram, the boundary line is marked using the threshold method (stress gradient ≤ 5 MPa / m).

[0174] A dynamic boundary is a region boundary in a force diffusion diagram where stress changes significantly with increasing load (stress gradient ≥ 15 MPa / m, greatly affected by load increment). For example, in the H-beam region within 1m of the point of force application, the stress increases from 50 MPa to 100 MPa (gradient 50 MPa / m), forming a dynamic boundary (longitudinal bridge x = 5~6m segment).

[0175] Connection units are the connecting components between construction units (including chemical anchors, welds, etc., which are key nodes for force transmission). For example, the fillet weld between the H-beam and the outer steel plate (connection unit C), and the chemical anchors between the outer steel plate and the old bridge (connection unit D).

[0176] A load-bearing unit is a unit that directly bears the construction load (such as a steel bridge deck bearing the self-weight of concrete).

[0177] Diffusion auxiliary force is the force received by the connecting unit and indirectly transmitted from the load-bearing unit (not a direct load, but a secondary component of force diffusion). For example, the load of the steel bridge deck (load-bearing unit) is transmitted to the H-beam through the weld (connecting unit), of which 30% is diffusion auxiliary force (70% is direct force).

[0178] A two-dimensional array is a table that records the changes in diffusion auxiliary force with "load step" and "location point" (row = load step, column = connection unit location point), for example, [[F11,F12],[F21,F22],...], where Fij is the diffusion auxiliary force (in kN) at the i-th load step and the j-th location point.

[0179] The dimension sequence is increased by traversing the array in the order of load step from smallest to largest (dimension 1) and position point from left to right (dimension 2).

[0180] A mutation sequence is a continuous data segment in a two-dimensional array where the diffusion assist force suddenly increases or decreases (change rate ≥ 20% / load step). For example, in the 2nd to 4th load steps, F21 = 10kN → F31 = 15kN → F41 = 22kN (change rates 50% and 47%), forming a mutation sequence.

[0181] The auxiliary static set is the diffusion auxiliary force data (force values ​​are stable and there are no mutations) before the first mutation sequence. For example, if the mutation sequence starts from the second loading step, the auxiliary force [8kN, 9kN] of the first loading step is the auxiliary static set.

[0182] The auxiliary dynamic set is the diffusion auxiliary force data of the mutation sequence and thereafter (the force value changes significantly with the load step). For example, the auxiliary forces [10kN, 15kN, 22kN] of the 2nd to 4th load steps are the auxiliary dynamic set.

[0183] The number of auxiliary force mutations is the number of times the rate of change of the auxiliary dynamic concentrated force value is ≥20% (reflecting the degree of instability in force transmission). For example, if there are 2 mutations in the auxiliary dynamic concentrated force (10→15kN, 15→22kN), the number of mutations is 2.

[0184] The dynamic calibration result is an evaluation of the stress stability of the construction unit based on the above indicators (such as "stable", "slight fluctuation", "drastic change"). For example, if the dynamic boundary of a certain H-beam is small (0.5m) and the number of abrupt changes in the auxiliary dynamic set is 1, the dynamic calibration result is "slight fluctuation". Specifically, the evaluation weights are set (dynamic boundary accounts for 30%, number of abrupt changes accounts for 40%, and static / dynamic set difference accounts for 30%), and the weighted scores are classified (such as ≥80 points for "stable").

[0185] The additional damage factor is a coefficient that quantifies the impact of damage terms on the cumulative damage of the structure (ranging from 0 to 1, with ≥0.8 indicating high risk). The total factor is obtained by summing the mapping relationship between damage terms and factors.

[0186] Damage items are key indicators extracted from dynamic calibration results that may lead to structural damage. They may include damage items of stress mutation type, damage items of mutation number type, and damage items of boundary anomaly type.

[0187] Damage items for stress mutation type: maximum stress mutation value Δσmax (stress difference between adjacent processes, unit MPa), mutation rate r = Δσ / Δt (unit MPa / h).

[0188] Mapping relationship (in a finite space, smaller patch widths are more sensitive to abrupt changes and have a stricter threshold):

[0189] interval Δσmax rule r rule Factor increment safe zone Δσ≤20MPa r≤5MPa / h 0 Warning Zone 20<Δσ≤30MPa 5<r≤10MPa / h Add 0.2 for every 5 MPa exceeding the limit. Danger Zone Δσ>30MPa r>10MPa / h Add 0.3 for every 5 MPa exceeding the limit.

[0190] Damage term based on mutation frequency: The damage term is the number of mutations n (the number of times the rate of change is ≥20%) in the auxiliary dynamic set. Mapping rule (for dense processes in a finite space with a strong cumulative effect of mutations, an exponential increase is adopted):

[0191] factor n1 = 0.15·n1 + 0.05×n1(n1-1)

[0192] Among them, 0.15·n1 is the basic increment, and 0.05×n1(n1-1) simulates the marginal effect.

[0193] Boundary anomaly damage items: Damage item: Dynamic boundary range D: Mapping rule (in finite space, the smaller the dynamic boundary, the more dangerous it is; the factor first increases and then decreases as D increases, because if it is too large, it will disperse the stress):

[0194]

[0195] Weighted summation of various damage factors (based on risk priority within a limited space, stress mutation has the highest weight, accounting for 50%; mutation frequency 30%; boundary anomaly 20%): Total Factor = 0.5 * Factor Δσ +0.3 factor n1 +0.2 factorD .

[0196] The beneficial effects of the above technical solution are as follows: by quantifying the force transmission characteristics and abrupt change laws at the connection of processes, and combining the construction characteristics of the spliced ​​structure (0.5~1.5m) in a limited space (such as small size and multiple processes), the damage risk index (additional damage factor) is accurately extracted, providing a quantitative basis for assessing the continuous damage of processes such as welding and concrete pouring. This effectively supports the technical goals of fast construction speed and high safety, and ensures the construction reliability of the spliced ​​structure in a narrow space.

[0197] This invention provides a simulation method for widening concrete bridge structures in confined spaces, determining the final vector direction, including:

[0198] Determine the unit three-dimensional structure of the construction unit and the edge three-dimensional connection structure of the unit three-dimensional structure;

[0199] The first initial position point of the unit solid structure is extracted based on the curvature extreme value detection algorithm. When there is an edge point based on the unit solid structure in the first initial position point, the edge point is regarded as the point to be analyzed.

[0200] Determine the second edge curvature of each point to be analyzed in the edge three-dimensional connection structure, and compare its magnitude with the first edge curvature of the corresponding edge point based on the unit three-dimensional structure;

[0201] If the second edge curvature is greater than the first edge curvature, the first initial position point is marked as a very important point; if the second edge curvature is equal to the first edge curvature, the first initial position point is marked as a normally important point; if the second edge curvature is less than the first edge curvature, the first initial position point is marked as a generally important point, wherein the priority of the very important point is greater than the priority of the normally important point, which is greater than the priority of the generally important point.

[0202] The regular important points and general important points are randomly split into N1 groups after being mixed, and then combined with very important points to obtain N1 sets of points.

[0203] Analyze the coplanarity of each point set and the uniqueness index of the position points between different point sets to select the best point set;

[0204] Along the direction of the keel structure line of the multi-scale-multi-constraint coupled finite element model, determine the first distance between the center reference point of each construction unit and the corresponding support point on the keel structure line;

[0205] Determine the number of deformation abrupt changes for the corresponding construction unit based on the applied force range, and determine the importance coefficient in conjunction with the first distance;

[0206] Determine the unit normal vector and importance coefficient for each location point in the optimal point set to obtain the corresponding simulation normal vector;

[0207] All simulation normal vectors are translated to the center reference point of the construction unit for vector fusion calculation to obtain the final vector direction.

[0208] In this embodiment, the unit three-dimensional structure is the three-dimensional geometric shape of the construction unit, including features such as length, width, height and cross-sectional shape. For example, the unit three-dimensional structure of H-beam is an "I-shaped cross-section three-dimensional body" with dimensions of 1m (length) × 0.2m (height) × 0.1m (width). Specifically, a three-dimensional model of the construction unit is established using BIM software (such as Revit) to accurately restore the cross-sectional dimensions and spatial shape.

[0209] The edge three-dimensional connection structure of the unit three-dimensional structure is the three-dimensional edge structure of the connection between the construction unit and the adjacent component, such as the welding edge of H-beam and outer steel plate, the overlapping edge of steel bridge deck and H-beam, for example, the welding edge of the lower flange of H-beam and outer steel plate (thickness 8mm), forming an "L-shaped three-dimensional connection structure" (H-beam flange width 100mm, outer steel plate edge cantilevered outward by 50mm). Specifically, based on the construction drawings, the edge contour of the connection part is refined in the three-dimensional model (such as weld height 6mm, bevel angle 45°).

[0210] In this embodiment, the curvature extremum detection algorithm is an algorithm that identifies key points of abrupt changes in structural geometry (usually stress concentration risk points) by calculating the maximum value of the surface curvature (degree of bending) of a component. Specifically, it uses the curvature analysis tool of 3D modeling software (such as Rhino) to set a curvature threshold (e.g., ≥5m). -1 ), extract points that exceed the threshold as initial position points.

[0211] The first initial position points are the initial key position points (reflecting abrupt changes in the geometric features of the structure) extracted from the unit solid structure by the curvature extreme value detection algorithm. For example, the flange end of the H-beam and the corner between the web and the flange. A total of 8 first initial position points are extracted.

[0212] The edge point of a unitary three-dimensional structure is a point located on the outer edge of the unitary three-dimensional structure (such as the edge of a component or the boundary point of its end face). For example, the outer edge point of the flange of an H-beam along its length, or the outer boundary point of a steel bridge deck.

[0213] The points to be analyzed are edge points selected from the first initial position points (because edge points are the connection parts, they are more sensitive to force transmission and need to be analyzed in detail). For example, the flange edge points (a total of 4) where the H-beam connects to the outer steel plate are marked as the points to be analyzed.

[0214] In this embodiment, the second edge curvature is the curvature of the point to be analyzed on the edge three-dimensional connection structure (reflecting the degree of bending at the connection point). For example, the point to be analyzed (weld corner) at the weld edge of the H-beam and the outer steel plate has a large curvature due to the weld bevel (45°), and the second edge curvature is 8m. -1 .

[0215] The first edge curvature is the curvature of the point to be analyzed on the edge of the unit solid structure itself (reflecting the degree of bending of the component's own edge). For example, the curvature of the point to be analyzed (when not welded) on the flange edge of an H-beam is 5m. -1 (Because of the right angle corner of the cross section.)

[0216] In this embodiment, a crucial point is the analysis of points where the curvature of the connecting structure is greater than that of the component itself (these pose the highest risk of stress concentration and require close monitoring), such as the corner point of the weld between the H-beam and the outer steel plate (second curvature 8m). -1 First curvature 5m -1 ), marked as very important points (2 in total).

[0217] Commonly important points: Points to be analyzed where the curvature of the connecting structure is equal to the curvature of the component itself (moderate risk of stress concentration), such as the straight section of the lap edge of the steel bridge deck and the H-beam (both have a curvature of 0), marked as commonly important points (3 in total).

[0218] Key points to analyze: Points where the curvature of the connecting structure is less than the curvature of the component itself (lower risk of stress concentration), such as the edge of the free end of an H-beam (curvature 5m). -1 (No connecting structure, second curvature 0), marked as a general important point (1 in total).

[0219] Priorities are ordered by importance to ensure that the mechanical response of high-priority points is considered first during simulation.

[0220] In this embodiment, the random splitting after mixing involves merging the regular important points and the general important points and then randomly dividing them into N1 groups (N1 is usually 3 to 5 to ensure the diversity of combinations). For example, there are 4 points: 3 regular important points + 1 general important point. These are randomly split into 2 groups (N1 = 2): the first group contains 2 regular points and the second group contains 1 regular point + 1 general point.

[0221] A point set is a combination of each set of split points and all very important points (ensuring that each set contains high-priority points to guarantee the comprehensiveness of the analysis). For example: the first set of points = 2 regular points + 2 very important points; the second set of points = 1 regular point + 1 general point + 2 very important points.

[0222] Coplanarity refers to whether all points in a point set are approximately located on the same plane (since construction units are mostly planar or near-planar components, point sets with high coplanarity can better reflect the overall force direction). For example, for point sets on the flange of an H-beam, if the maximum distance from the point to the plane is ≤5mm, the coplanarity meets the standard through plane fitting calculation. Specifically, the least squares method is used to fit the plane, and the distance deviation from the point set to the plane is calculated. A deviation ≤10mm is considered acceptable.

[0223] The uniqueness index of a location point is the percentage of "unique points" (points contained only in a certain group) among different point sets (formula: uniqueness index = number of unique points / total number of points in the group), which needs to be ≥0.6 (to avoid point set redundancy). For example, if the first group has 2 unique points and a total of 4 points, the uniqueness index = 2 / 4 = 0.5 (not up to standard); after adjustment, there are 3 unique points, and the uniqueness index = 3 / 5 = 0.6 (up to standard).

[0224] The optimal point set is the set that meets the coplanarity standard and has the highest uniqueness index (ensuring that the point set can reflect the overall characteristics of the component and contain unique key information).

[0225] In this embodiment, the keel structure line is the main load-bearing axis of the widening structure (such as the center line of the H-beam support along the longitudinal direction of the bridge, which is the "skeleton" of the structure). For example, one H-beam is arranged every 1m along the longitudinal direction of the bridge, and the center lines of the H-beams are connected to form the keel structure line (0.8m from the edge of the old bridge).

[0226] The central reference point is the three-dimensional coordinate point of the geometric center (centroid) of the construction unit (serving as the reference origin for analysis). For example, the central reference point of the H-beam is its cross-sectional centroid, with coordinates (x0, y0, z0) = (5m, 0.5m, 0.1m) (at x = 5m along the longitudinal direction of the bridge).

[0227] The corresponding support point on the keel structure line is the point on the keel structure line that supports the construction unit (such as the connection node of adjacent H-beams, the fixing point of the outer steel plate). For example, the support point of the H-beam is the connection point between its two ends and the adjacent components, with coordinates (x0, y0, z0) = (5m, 0, 0.1m).

[0228] The first distance is the straight-line distance from the center reference point to the corresponding support point (the closer the distance, the more significant the support effect, and the higher the importance of the point). For example, the first distance between the center reference point and the support point is 0.5m (reflecting the leverage effect of the H-beam).

[0229] In this embodiment, the number of deformation mutations is the number of times that the deformation (such as deflection and strain) of the construction unit suddenly increases due to the increase of load within the force application range (mutation definition: the deformation difference between adjacent load steps is ≥10%). For example, during the pouring of C40 concrete for H-beams (loaded in 3 steps), the deflection suddenly increases from 5mm to 8mm (difference of 60%) during the second loading step, and the number of mutations is recorded as 1.

[0230] The importance coefficient is a weighted coefficient that combines the first distance and the number of deformation mutations (the closer the distance and the more mutations, the larger the coefficient, reflecting the more significant the influence of the point on the overall force). Importance coefficient = first distance / set maximum distance × 0.6 + number of deformation mutations / upper limit of mutations × 0.4, where the maximum distance is the length of the bridge.

[0231] The unit normal vector is a unit vector perpendicular to the surface of the construction unit (the direction is perpendicular to the tangent plane at the point, reflecting the surface orientation). For example, the unit normal vector of the upper flange surface of an H-beam is vertically upward (positive z-axis direction), and that of the lower flange is vertically downward (negative z-axis direction). Specifically, the unit normal vector (accuracy ±0.5°) of each location point is extracted using the normal vector calculation tool of the 3D modeling software.

[0232] The simulation normal vector is the product of the unit normal vector and the importance coefficient of that point (giving greater weight to points of high importance and strengthening their influence on the overall direction). For example, if the unit normal vector of a very important point is (0,0,1) (vertically upward) and the importance coefficient is 1.6, its simulation normal vector is (0,0,1.6).

[0233] In this embodiment, translating to the central reference point involves geometrically translating the simulated normal vectors of each point (without changing their direction or magnitude) so that the starting point of all vectors is the central reference point (for ease of synthesis).

[0234] Vector fusion calculation combines multiple simulated normal vectors into a final vector (reflecting the overall force direction of the construction unit) by weighted averaging (weights being importance coefficients). For example, if three simulated normal vectors are (0,0,1.6), (0,0,1.2), and (0,0,0.8), the final fused vector is (0,0,(1.6+1.2+0.8) / 3)=(0,0,1.2) (vertically upward). Specifically, vector algebra is used to sum the components of each simulated normal vector and then take the average to obtain the direction parameters of the final vector (e.g., the angle with the z-axis ≤5°).

[0235] The beneficial effects of the above technical solution are: by accurately identifying the key location points of the construction unit through curvature analysis, by combining the support relationship and deformation characteristics of the keel structure to determine the importance of the points, and by obtaining the force direction of the construction unit (such as the force application direction and the normal response direction) through vector fusion, the accuracy of mechanical simulation of the widened structure (such as H-beams and steel bridge decks) in a limited space is significantly improved, providing a reliable directional reference for subsequent load application and stress analysis.

[0236] This invention provides a simulation method for widening concrete bridge structures in confined spaces. It iterates through the range of each required parameter in the simulation results and, based on the three-dimensional target system, analyzes and determines the parameter combination that achieves mechanical compliance and minimizes spatial redundancy. The method includes:

[0237] Extract the set of parameters to be optimized from the simulation results. The set of parameters to be optimized includes: H-beam spacing, chemical anchor diameter, UHPC casting thickness, and steel mesh reinforcement ratio.

[0238] Set a finite space hard constraint threshold for each parameter:

[0239] H-beam spacing ≥ 0.6m;

[0240] Chemical anchors with a diameter ≤18mm;

[0241] UHPC casting thickness ≤ 10cm;

[0242] The steel mesh reinforcement ratio is ≤2.0%;

[0243] A three-dimensional adaptation function F based on mechanics-space-construction is established: F=∝1·f(σL)+∝2·g(σK)+∝3·g(σS). Candidate parameter sets are determined and substituted into the candidate parameter sets into a multi-scale-multi-constraint coupled finite element model. The construction and operation stages are re-simulated to obtain the optimal combination. Here, ∝1, ∝2, and ∝3 represent weights, and f(σL), g(σK), and g(σS) represent the mechanical performance compliance function, spatial compliance redundancy function, and construction feasibility efficiency function, respectively.

[0244] In this embodiment, mechanical safety is the most critical factor in the confined space, so ∝1>∝2>∝3, with values ​​of ∝1=0.5, ∝2=0.3, and ∝3=0.2.

[0245]

[0246] Where σL, σK, and σS represent stress, spatial redundancy length, and process time, respectively; t represents the set duration.

[0247] The beneficial effects of the above technical solution are: through a closed-loop process of locking the bottom line with hard constraints (parameter thresholds) + soft adaptation to balance the target (three-dimensional function) + full-stage verification (re-simulation of construction + operation), it achieves controllable mechanical safety, maximizes space utilization, and improves construction efficiency, providing a precise and efficient technical path for small-size splicing (0.5~1.5m).

[0248] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A simulation method for widening concrete bridge structures in confined spaces, characterized in that, include: Step 1: Construct a multi-scale-multi-constraint coupled finite element model of the splicing structure adapted to the limited space, wherein the multi-scale-multi-constraint coupled finite element model includes the existing bridge structure, the newly added steel-concrete composite splicing structure and the connection nodes between the two. Step 2: Define the multi-dimensional simulation boundary conditions driven by the finite space. The multi-dimensional simulation boundary conditions include: existing bridge foundation constraints, the range of temporary loads during the construction of the widened structure, the surrounding environmental limits, and the time-varying parameters of the materials. Step 3: Perform a phased coupled simulation analysis under confined space conditions, where the phases include: construction phase and operation phase; Step 4: Based on the simulation results, perform multi-objective optimization iterations for the limited space constraints, and prioritize the selection of parameter combinations that meet mechanical requirements and have the least spatial redundancy for practical application in concrete bridge widening structures.

2. The simulation method for widening concrete bridge structures in confined spaces according to claim 1, characterized in that, Step 1 includes: A BIM platform was used to construct an integrated geometric-physical information model of the existing bridge and the widening structure, and finite space constraint parameters were defined. The integrated finite element method (FEM) software is used to perform mechanical simulations on the integrated geometric-physical information model. A parametric interface enables bidirectional data-driven operation between the BIM model and the finite element mesh. Existing bridges are simulated using solid elements, refining the geometric contours of the old bridge edges as geometric constraints for construction within a limited space. In the newly added steel-concrete composite widening structure, the steel bridge deck uses shell elements, the H-shaped steel supports, and the concrete layer uses solid elements, simulating the gradual stiffness variation effect at the steel-concrete interface. Chemical anchors in the connection nodes are limited by embedded spring element groups to ensure minimum spacing within a limited space, and the spring stiffness is calibrated through pull-out tests. Welded nodes in the connection nodes are based on the established local microscopic solid model and a transition element area for the weld region, simulating the thermo-mechanical coupling effect of welding heat input on the existing concrete. Based on the mechanical simulation results, a cross-scale model of the bridge as a whole, node structure, and material interface is constructed. The influence of finite space constraints on mechanical response is transmitted through a reduced-order model, resulting in a multi-scale-multi-constraint coupled finite element model.

3. The simulation method for widening concrete bridge structures in confined spaces according to claim 1, characterized in that, Perform staged coupled simulation analysis under finite space conditions, including: Welding simulation was performed on narrow gaps in H-beams. The welding simulation was based on thermo-mechanical coupling analysis, which calculated the temperature field of the existing concrete and the extrusion stress at the edge of the old bridge due to the welding thermal cycle. We conducted a casting simulation of thin-layer UHPC, in which a rheological model was introduced to analyze the weakening effect of self-weight leveling on the bond strength of the steel-concrete interface, and quantified the chain effect of construction space, material properties and mechanical response. Mechanical response simulation was performed on the interleaved construction processes, including simulating the sequence of external steel plate installation, H-beam welding, and concrete pouring, calculating the stress mutation value at the connection of the processes, and assessing the risk of damage to the structure due to construction continuity. Among them, the welding simulation results, casting simulation results, and mechanical response simulation results are simulation results of the construction stage.

4. The simulation method for widening concrete bridge structures in confined spaces according to claim 3, characterized in that, Performing phased coupled simulation analysis under finite space conditions also includes: The vehicle was subjected to eccentric load simulation. In particular, for the narrowing of the bridge deck after the bridge was widened, the eccentric load coefficient was used to amplify the concentrated lateral load of the vehicle and to extract the fatigue stress amplitude of the welded area between the steel bridge deck and the H-beam. Coupled simulation of temperature and impact was performed, which simulated the synergistic effect of temperature gradient enhancement and SB-level guardrail impact in a confined space, and calculated the lateral displacement and nodal impact stress of the widened structure. Among them, the off-center load simulation results and the coupled simulation results are simulation results from the operation phase.

5. The simulation method for widening concrete bridge structures in confined spaces according to claim 1, characterized in that, Step 4 includes: Establish a multi-objective system based on the constraints of mechanical performance, spatial compliance, and construction feasibility in a confined space. The range of each required parameter in the simulation results is traversed, and the parameter combination that achieves mechanical compliance and minimizes spatial redundancy is determined based on the analysis of the multi-objective system with the finite space constraints.

6. The simulation method for widening concrete bridge structures in confined spaces according to claim 3, characterized in that, The process of calculating stress abrupt changes at the junctions of construction processes and assessing the risk of structural damage due to construction continuity includes: Based on the structural type of the sub-construction structure under each process and the connection relationship of each construction unit in the sub-construction structure, the unit array of the construction unit is determined. The unit array includes the construction unit connected to the corresponding construction unit, the position status and attribute status of the connected construction unit, the unit position of the corresponding construction unit based on the sub-construction structure, and the unit material. The unit array is input into the force analysis model to obtain the force application range. Based on the force application range, the force is applied to the corresponding construction unit and the construction unit in the equivalent force model composed of connecting units one by one to obtain the force diffusion diagram of the corresponding equivalent force model. The force application direction is the final vector direction under the simulation normal vector of the corresponding construction unit and the force application position point is the center reference point of the corresponding construction unit. The force diffusion diagrams under the same construction unit are sequentially projected into a three-dimensional coordinate system to determine the static and dynamic boundaries of each construction unit in the equivalent force model. The corresponding construction unit is determined to be the diffusion auxiliary force of the simulated force applied by the same force unit under the connection unit, and a two-dimensional array is constructed. The second array is then fitted and the mutation sequence is screened in a sequential manner according to the dimension sequence increasing one by one. The auxiliary diffusion forces before the first occurrence of the mutation sequence are taken as the auxiliary static set, and the auxiliary diffusion forces in the remaining sequences are taken as the auxiliary dynamic set. The number of auxiliary force mutations that occur in the auxiliary dynamic set is counted. Based on static and dynamic boundaries, all auxiliary static sets, auxiliary dynamic sets, and auxiliary force mutation times involved, the dynamic calibration results of the corresponding construction unit are obtained; Damage items are extracted from all dynamic calibration results under the sub-construction results to obtain additional damage factors for the corresponding process to assist in the assessment of damage risk.

7. The simulation method for widening concrete bridge structures in confined spaces according to claim 6, characterized in that, Determining the final vector direction includes: Determine the unit three-dimensional structure of the construction unit and the edge three-dimensional connection structure of the unit three-dimensional structure; The first initial position point of the unit solid structure is extracted based on the curvature extreme value detection algorithm. When there is an edge point based on the unit solid structure in the first initial position point, the edge point is regarded as the point to be analyzed. Determine the second edge curvature of each point to be analyzed in the edge three-dimensional connection structure, and compare its magnitude with the first edge curvature of the corresponding edge point based on the unit three-dimensional structure; If the second edge curvature is greater than the first edge curvature, the first initial position point is marked as a very important point; if the second edge curvature is equal to the first edge curvature, the first initial position point is marked as a normally important point; if the second edge curvature is less than the first edge curvature, the first initial position point is marked as a generally important point, wherein the priority of the very important point is greater than the priority of the normally important point, which is greater than the priority of the generally important point. The regular important points and general important points are randomly split into N1 groups after being mixed, and then combined with very important points to obtain N1 sets of points. Analyze the coplanarity of each point set and the uniqueness index of the position points between different point sets to select the best point set; Along the direction of the keel structure line of the multi-scale-multi-constraint coupled finite element model, determine the first distance between the center reference point of each construction unit and the corresponding support point on the keel structure line; Determine the number of deformation abrupt changes for the corresponding construction unit based on the applied force range, and determine the importance coefficient in conjunction with the first distance; Determine the unit normal vector and importance coefficient for each location point in the optimal point set to obtain the corresponding simulation normal vector; All simulation normal vectors are translated to the center reference point of the construction unit for vector fusion calculation to obtain the final vector direction.

8. The simulation method for widening concrete bridge structures in confined spaces according to claim 5, characterized in that, The range of each required parameter in the simulation results is traversed, and the parameter combination that achieves mechanical compliance and minimizes spatial redundancy is determined based on the three-dimensional target system, including: Extract the set of parameters to be optimized from the simulation results. The set of parameters to be optimized includes: H-beam spacing, chemical anchor diameter, UHPC casting thickness, and steel mesh reinforcement ratio. Set a finite space hard constraint threshold for each parameter: H-beam spacing ≥ 0.6m; Chemical anchors with a diameter ≤18mm; UHPC casting thickness ≤ 10cm; The steel mesh reinforcement ratio is ≤2.0%; A three-dimensional adaptation function F based on mechanics-space-construction is established: F=∝1·f(σL)+∝2·g(σK)+∝3·g(σS). Candidate parameter sets are determined and substituted into the candidate parameter sets into a multi-scale-multi-constraint coupled finite element model. The construction and operation stages are re-simulated to obtain the optimal combination. Here, ∝1, ∝2, and ∝3 represent weights, and f(σL), g(σK), and g(σS) represent the mechanical performance compliance function, spatial compliance redundancy function, and construction feasibility efficiency function, respectively.

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