Finite element rapid modeling and bearing capacity early warning threshold setting method for hollow slab girder

Abstract

The invention discloses a hollow slab beam finite element rapid modeling and bearing capacity early warning threshold setting method, and belongs to the bridge structure health detection technology. The method comprises the following steps: firstly, establishing a single-beam model and a transverse distribution model of the hollow slab girder bridge based on bridge doctor software, namely calculating transverse distribution of a load by adopting a transverse hinged plate theory, and analyzing a transverse distribution rule of a mid-span load by adopting a half-wave sine load; calculating a single-beam deflection value and a transverse distribution coefficient under an automobile load; and then based on a calculation result of the finite element model, obtaining a deflection value of each piece of beam, and providing a reference for setting a bridge health monitoring early warning threshold value. According to the method, finite element modeling analysis can be carried out, the number of monitoring points is reduced from bearing capacity analysis of the hollow beam, monitoring data redundancy is reduced, the data processing efficiency is improved, meanwhile, the data size is effectively reduced, and the data storage and transmission cost is reduced.

Description

Technical Field

[0001] The present invention belongs to bridge structure health detection and analysis technology, and specifically relates to a hollow slab beam finite element rapid modeling and bearing capacity warning threshold setting method. Background Art

[0002] In order to ensure the safety, integrity and durability of bridge structures and prevent accidents before they happen, it is a very effective technical means to use bridge safety monitoring technology to conduct real-time safety monitoring, early warning and evaluation of the response of the structural state and environmental conditions of the bridge to external loads and other factors. For bridges with large spans and special structures, some have adopted safety monitoring technology during the construction and operation periods to monitor and evaluate the safety status of bridges, and the corresponding specifications are relatively mature. However, for small and medium span bridges, except for organizing regular inspections and inspections every year in accordance with the requirements of bridge maintenance specifications, no corresponding bridge safety monitoring technology has been adopted. The research and application of key safety monitoring technologies for small and medium span bridges is still in its infancy.

[0003] For small and medium span bridge structures, the deflection deformation under load is the main parameter for quantitative evaluation of bearing capacity. Due to the different distances of reference points, deflection testing is currently divided into non-contact methods and contact methods. Non-contact methods include level / total station, machine vision, laser / LED testing, radar, etc. Contact methods mainly include inclinometers, displacement sensors, etc.

[0004] At present, monitoring units mainly use photoelectric deflectometers to monitor vertical displacement. The non-contact full-field optical measurement method based on modern digital image processing and analysis can realize all-weather collection, automatic and rapid transmission, real-time processing and analysis, and graphical display of monitoring information for the displacement data of the monitoring target. However, for hollow slab beam bridges, there are no clear regulations on the layout of measuring points, and measuring points are often arranged at the bottom of each beam. There are many measuring points, and the equipment procurement and maintenance costs are high. Therefore, reducing the layout of measuring points, or maintaining the deflection warning capability after some measuring points fail, is an urgent problem to be solved. Summary of the invention

[0005] Purpose of the invention: In view of the above problems, the present invention aims to provide a method for rapid finite element modeling of hollow slab beams and setting bearing capacity thresholds, thereby reducing the number of measuring points arranged on the bridge and maintaining the deflection warning capability after some measuring points fail.

[0006] Technical solution: A method for rapid finite element modeling of hollow slab beams and setting of bearing capacity warning threshold, the method comprising:

[0007] Finite element model calculation: Based on the Bridge Doctor software, the single beam model and lateral distribution model of the hollow slab beam bridge are established, including the use of the transverse hinged plate theory to calculate the lateral distribution of the load, and the use of half-wave sine load to analyze the law of the lateral distribution of the mid-span load, so as to calculate the deflection value and lateral distribution coefficient of the single beam under the vehicle load;

[0008] Bearing capacity warning threshold setting: Based on the calculation results of the finite element model, the deflection value of each beam is obtained, and a reference is provided for the setting of bridge health monitoring warning thresholds.

[0009] Furthermore, the method includes modeling through the following steps:

[0010] (1) The bridge span structure is a spatial structure composed of several hollow slab beams. It is simplified into a plane problem, and the joint gap of the hollow slab beams is regarded as a hinge. Under the action of vertical load, only vertical shear force is transmitted in the joint, and half-wave sine load is used to analyze the law of lateral distribution of mid-span load;

[0011] (2) The calculation of the lateral distribution of loads on an articulated slab bridge includes the calculation of the load distributed to any hollow slab girder in the bridge structure when the load force P acts on the centerline of each slab girder;

[0012] (3) Based on the Bridge Doctor finite element software, the hinged plate beam method is selected to establish a lateral distribution model, obtain the lateral distribution coefficient diagram of each beam, and establish the lateral distribution influence matrix of the vehicle load for data processing and analysis;

[0013] (4) Based on the Bridge Doctor finite element calculation software, a single-beam model of the hollow slab girder bridge is established, and the deflection value under single-lane load is calculated and analyzed.

[0014] The method for setting the bearing capacity warning threshold is as follows:

[0015] 1) Based on the finite element calculation results of the single beam of the hollow slab bridge, the deflection calculation results under vehicle load are obtained;

[0016] 2) Calculate the deflection value of each beam through the lateral distribution influence matrix;

[0017] 3) During the installation phase of the photoelectric deflectometer, select locations with large displacement response and safe sensor operation to set up measurement points;

[0018] 4) Monitor the displacement results of beams with installed sensors, calculate the deflection value of each beam according to the lateral distribution influence matrix; and set multi-level bridge vertical displacement warning thresholds to provide accurate and reliable warning information for the long-term safe operation of bridge structures;

[0019] When the vertical displacement of the main beam at the measuring point reaches 0.8 times the design value, it is a second-level over-limit, and when it reaches the design value, it is a third-level over-limit; the warning thresholds for the remaining hollow slab beams are converted proportionally according to the size of the lateral distribution coefficient.

[0020] 5) During the operation phase, if some measuring points fail or data is abnormal, the missing measuring points or abnormal data are verified based on the lateral distribution influence matrix.

[0021] Furthermore, this method regards the joint gap of the hollow slab beam as a hinge. When there is a force P at the joint gap, the longitudinal shear force, normal force and transverse bending moment are ignored, and only the vertical shear force is transmitted. For the bridge span structure which is a spatial structure composed of several hollow slab beams, the spatial calculation problem is simplified into a plane problem based on the principle of determining the transverse distribution of the load based on the transverse deflection distribution law, and the longitudinal shear force t(x), normal force n(x) and transverse bending moment m(x) generated at this position are ignored, and only the vertical shear force g(x) is considered. Under the action of P, the ratio of the load P(x) and the deflection W(x) allocated to any two slab beams, and the ratio of the cross-sectional internal forces M(x) and V(x) are the same.

[0022] Furthermore, the calculation of the lateral load distribution of the hinged slab bridge includes the bending moment of inertia I and the torsional moment of inertia I of the hollow slab section. T , stiffness parameter γ, and then consult the influence line calculation table of the lateral distribution of hinged plate load, and obtain the vertical value of the influence line by linear interpolation.

[0023] Beneficial effects: The method of the present invention reduces installation and maintenance costs and monitoring costs by optimizing the arrangement of the number of sensors; reduces the redundancy of monitoring data by reducing the number of monitoring points, improves data processing efficiency, and effectively reduces the amount of data, thereby reducing data storage and transmission costs; the present invention can also improve the efficiency of troubleshooting data abnormality measurement points and provide additional monitoring data during the maintenance of failed measurement points. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The calculation process framework diagram of the method described in the present invention;

[0025] Figure 2 It is a schematic diagram of the forces acting on the hinged plate;

[0026] Figure 3 is the lateral distribution coefficient of vehicle load;

[0027] Figure 4 It is the finite element model of a single beam of hollow slab under single lane load;

[0028] Figure 5 It is the deflection value of the hollow slab beam under single lane load. DETAILED DESCRIPTION

[0029] To illustrate the technical solution provided by the present invention in detail, a further introduction is given below in conjunction with the accompanying drawings.

[0030] The present invention provides a hollow slab beam finite element rapid modeling and bearing capacity threshold setting method, combined with Figure 1 As shown, it mainly includes two stages:

[0031] Phase I: Finite element model calculation. Based on the Bridge Doctor software, the single beam model and lateral distribution model of the hollow slab beam bridge are established to calculate the single beam deflection value and lateral distribution coefficient under vehicle load.

[0032] The second stage: setting of bearing capacity warning threshold, based on the finite element calculation results, considering P acting on different plate beams, other plate beams near the plate beam will participate in the force. Bridge Doctor will arrange vehicle loads according to the most unfavorable situation. The calculation results can obtain the maximum deflection of each plate beam, and thus the deflection value of each beam, and provide a reference for the setting of bridge health monitoring warning threshold.

[0033] Specifically, the implementation steps of the present invention include:

[0034] S1. Modeling by hinged plate method in Bridge Doctor finite element software

[0035] For hollow slab beam bridges, since there is a certain transverse connection structure between the beams, but the structural rigidity is relatively weak, the stress state of this type of structure is actually close to that of several parallel and transversely hinged narrow plates (beams), and the transversely hinged plate (beam) theory is used to calculate the transverse distribution of load.

[0036] For hollow slab beam bridges, since there is a certain transverse connection structure between the beams, but the structural rigidity is relatively weak, the stress state of this type of structure is actually close to that of several parallel and transversely hinged narrow plates (beams), and the transversely hinged plate (beam) theory is used to calculate the transverse distribution of load.

[0037] For the present invention, we make the following assumptions and analyses:

[0038] ① Under the action of vertical load, only vertical shear force is transmitted in the joint.

[0039] ② Use half-wave sinusoidal load to analyze the lateral distribution law of mid-span load.

[0040] like Figure 2As shown, when the plate beam is subjected to the action P, the joint of the plate beam will generate: vertical shear g(x), longitudinal shear t(x), normal force n(x), and transverse bending moment m(x). Considering the impact on the health of the bridge structure and maximizing the monitoring effect and economy, the longitudinal shear t(x) and normal force n(x) have a very small impact on the plate beam compared with the vertical shear g(x), and the present invention ignores them. Since the height of the joint is not large and the rigidity is very small, the transverse bending moment m(x) transmitted is also very small and can be ignored. Therefore, the joint can be regarded as a hinge, which only transmits the vertical shear g(x).

[0041] The bridge span structure is a spatial structure composed of several beams. Since the analysis and calculation of the spatial structure is relatively complex, in order to simplify the calculation, the spatial calculation problem needs to be simplified into a plane problem by using the law of lateral deflection distribution to determine the principle of lateral distribution of load. Strictly speaking, under the action of P, the ratio of the load P(x) and the deflection W(x), the section bending moment M(x), and the shear force V(x) assigned to any two plate beams are the same.

[0042] Based on the above assumptions and analysis, the load distributed to any plate when P = 1 acts on the center axis of each plate is further calculated, including the calculation of the bending moment of inertia I and the torsional moment of inertia I of the hollow plate section. T , stiffness parameter γ, and then consult the influence line calculation table of the lateral distribution of hinged plate load, and obtain the vertical value of the influence line by linear interpolation.

[0043] Furthermore, based on the Bridge Doctor finite element software, a lateral distribution model is established, and the steps include:

[0044] 1) Create a new lateral distribution coefficient model and select the rigid (hinged) plate beam method;

[0045] 2) In the structure description module, fill in the main beam parameters;

[0046] 3) In the load information module, select the 2015 Highway Bridge Code as the calculation specification, check the option to automatically include the vehicle lane load coefficient, and determine the most unfavorable load position along the transverse direction according to the "General Code" (JTG D60-2015). The transverse distribution coefficient of each hollow slab beam under the most unfavorable load can be calculated;

[0047] 4) Query the results of the lateral distribution coefficient, and output the lateral distribution coefficient of automobile load for different plate beams. Taking the middle beam as an example, the distribution diagram is as follows: Figure 3 shown.

[0048] According to this, we can get Figure 4The finite element model of a hollow slab beam under a single lane (single slab beam) load is shown in the figure. Based on the lateral distribution coefficient diagram of each beam, the lateral distribution influence matrix of the vehicle load is established for data processing and analysis. Based on the Bridge Doctor finite element calculation software, a single beam model of a hollow slab beam bridge is established, and the deflection value under a single lane load is calculated and analyzed. The following can be obtained: Figure 5 The deflection values ​​of a single hollow slab beam under a single lane load are shown.

[0049] Based on the calculation results of the finite element model established above and the deflection values ​​of each beam, the bearing capacity warning threshold can be set to provide a reference for the setting of the bridge health monitoring warning threshold. The steps include:

[0050] 1) Based on the finite element calculation results of the single beam of the hollow slab bridge, the deflection calculation results under vehicle load are obtained;

[0051] 2) Calculate the deflection value of each beam through the lateral distribution influence matrix;

[0052] 3) During the installation phase of the photoelectric deflectometer, select locations with large displacement response and safe sensor operation to set up measurement points;

[0053] 4) Monitor the displacement results of beams with installed sensors, and calculate the deflection value of each beam according to the lateral distribution influence matrix. Set multi-level bridge vertical displacement warning thresholds to provide accurate and reliable warning information for the long-term safe operation of bridge structures.

[0054] 5) During the operation phase, if some measuring points fail or data is abnormal, the missing measuring points or abnormal data are verified based on the lateral distribution influence matrix.

[0055] Traditional bridge structure health detection technology includes the use of inclinometers for detection. When measuring dynamic deflection, the inclinometer has high requirements for transient response and zero drift. The limited range cannot measure large-span bridges with a large range of inclination changes, such as extra-large suspension bridges and cable-stayed bridges. In the detection technology of displacement sensors, the hanging hammer method cannot ignore the influence of the shaking of flexible ropes and heavy hammers, and is limited to static testing. The scaffolding method has high economic and time costs. The present invention uses finite element rapid modeling for the deflection hollow slab beams of small and medium span hollow slab beam bridges, and realizes the setting of bearing capacity thresholds based on model analysis.

Claims

1. A method for rapid finite element modeling of hollow slab beams and setting of bearing capacity warning threshold, characterized in that: The method includes: Finite element model calculation: Based on the Bridge Doctor software, the single beam model and lateral distribution model of the hollow slab beam bridge are established, and then the lateral articulated plate theory is used to calculate the lateral distribution of the load. The half-wave sine load is used to analyze the law of the lateral distribution of the mid-span load, and the deflection value and lateral distribution coefficient of the single beam under the automobile load are obtained; Bearing capacity warning threshold setting: Based on the calculation results of the finite element model, the deflection value of each beam is obtained, which provides a reference for the setting of bridge health monitoring warning thresholds.

2. The method for rapid finite element modeling and bearing capacity warning threshold setting of hollow slab beam according to claim 1 is characterized in that: The method involves modeling through the following steps: (1) The bridge span structure is a spatial structure composed of several hollow slab beams. It is simplified into a plane problem, and the joint gap of the hollow slab beams is regarded as a hinge. Under the action of vertical load, only vertical shear force is transmitted in the joint, and half-wave sine load is used to analyze the law of lateral distribution of mid-span load; (2) The calculation of the lateral distribution of loads on an articulated slab bridge includes the calculation of the load distributed to any hollow slab girder in the bridge structure when the load force P acts on the centerline of each slab girder; (3) Based on the Bridge Doctor finite element software, the hinged plate beam method is selected to establish a lateral distribution model, obtain the lateral distribution coefficient diagram of each beam, and establish the lateral distribution influence matrix of the vehicle load for data processing and analysis; (4) Based on the Bridge Doctor finite element calculation software, a single-beam model of the hollow slab girder bridge is established, and the deflection value under single-lane load is calculated and analyzed.

3. The method for rapid finite element modeling and bearing capacity warning threshold setting of hollow slab beam according to claim 2 is characterized in that: The method for setting the bearing capacity warning threshold is as follows: 1) Determine the calculation results of deflection under load based on the finite element calculation results of the single beam of the hollow slab bridge; 2) Calculate the deflection value of each beam through the lateral distribution influence matrix; 3) During the installation phase of the photoelectric deflectometer, a hollow slab beam with a large relative displacement response is selected to set up the photoelectric deflectometer, and the measuring points are arranged at a location where the sensor is safe for operation; 4) Monitor the displacement results of the beams with installed sensors, and calculate the deflection value of each beam according to the lateral distribution influence matrix; It also sets multi-level bridge vertical displacement warning thresholds to provide accurate and reliable warning information for the long-term safe operation of bridge structures; 5) During the operation phase, if some measuring points fail or data is abnormal, the missing measuring points or abnormal data are verified based on the lateral distribution influence matrix.

4. The method for rapid finite element modeling and bearing capacity warning threshold setting of hollow slab beam according to claim 2 or 3, characterized in that: This method regards the joint gap of the hollow slab beam as a hinge. When there is a force P at the joint gap, the longitudinal shear force, normal force and transverse bending moment are ignored, and only the vertical shear force is transmitted. For the bridge span structure which is a spatial structure composed of several hollow slab beams, the spatial calculation problem is simplified into a plane problem based on the principle of determining the transverse distribution of the load based on the transverse deflection distribution law, and the longitudinal shear force t(x), normal force n(x) and transverse bending moment m(x) generated at this position are ignored, and only the vertical shear force g(x) is considered. Under the action of P, the ratio of the load P(x) and the deflection W(x) allocated to any two slab beams, as well as the ratio of the cross-sectional internal forces M(x) and V(x) are the same.

5. The method for rapid finite element modeling and bearing capacity warning threshold setting of hollow slab beam according to claim 2 or 3, characterized in that: The calculation of the lateral distribution of load on the hinged plate bridge includes the bending moment of inertia, torsional moment of inertia and stiffness parameters of the hollow plate section. Then, the influence line calculation table of the lateral distribution of load on the hinged plate is consulted, and the vertical value of the influence line is obtained by linear interpolation.

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