Large-span stiff skeleton arch bridge skewback foundation mass concrete crack control method

Abstract

The invention discloses a large-span stiff skeleton arch bridge skewback foundation mass concrete crack control method, and relates to the technical field of bridge engineering, and the system comprises the following components: S1, building a collaborative analysis model, S2, analyzing deformation influence, and S3, implementing crack control measures. The method has high pertinence and practicability by adjusting the concrete mix proportion, adding the admixture, setting temperature control measures and optimizing the reinforcement design, the concrete mix proportion and the cement dosage can be adjusted in a targeted mode through the concrete stress distribution condition and the stiff skeleton deformation condition obtained through the collaborative analysis model, and the construction efficiency is improved. The additive is added to reduce the adverse effect of hydration heat, meanwhile, effective temperature control measures are set according to the temperature field distribution condition, in addition, by optimizing the reinforcement design, the bearing capacity and crack resistance of the skewback foundation can be further improved, the crack risk of large-size concrete of the skewback foundation of the large-span stiff skeleton arch bridge is effectively reduced, and the service life of the large-span stiff skeleton arch bridge is prolonged. And the overall quality and safety of a project are improved.

Description

Technical Field

[0001] The invention relates to the technical field of bridge engineering, in particular to a method for controlling cracks in a large-volume concrete of an arch seat foundation of a large-span rigid skeleton arch bridge. Background Art

[0002] As an important structural form in modern bridge engineering, crack control of large-volume concrete in the arch foundation of large-span rigid skeleton arch bridges has always been a key issue of concern in the engineering community. This type of bridge has a complex structure and variable stress state, especially in the arch foundation part. Due to the huge load and complex deformation, cracks are very likely to occur, thus affecting the overall safety and durability of the bridge. The generation of cracks will not only reduce the bearing capacity of the structure, but also accelerate the aging and corrosion of concrete, shortening the service life of the bridge.

[0003] The traditional method for controlling cracks in large-volume concrete of the arch seat foundation of large-span rigid frame arch bridges has shortcomings. On the one hand, it cannot accurately predict and optimize the control of cracks in large-volume concrete of the arch seat foundation of large-span rigid frame arch bridges. On the other hand, it cannot comprehensively consider the coordinated deformation relationship between the arch seat foundation and the rigid frame, as well as the actual load conditions and ambient temperature changes during construction and operation.

[0004] In summary, the traditional method of controlling cracks in large-volume concrete of the arch seat foundation of large-span rigid skeleton arch bridges has many shortcomings and is difficult to meet the high requirements of crack control in modern bridge engineering. Therefore, it is particularly important to develop a method of controlling cracks in large-volume concrete of the arch seat foundation of large-span rigid skeleton arch bridges. Summary of the invention

[0005] The purpose of the present invention is to make up for the deficiencies of the prior art and to provide a method for controlling cracks in large-volume concrete of the arch seat foundation of a large-span rigid skeleton arch bridge. The method constructs a collaborative analysis model by adopting an architecture based on the fusion of finite element theory and neural network algorithm, thereby achieving accurate prediction and dynamic optimization of structural deformation and stress distribution, and providing a new solution for crack control in bridge engineering.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for controlling cracks in large-volume concrete of arch seat foundation of a large-span rigid skeleton arch bridge, the specific steps of the method are:

[0007] S1, Establishment of collaborative analysis model: A collaborative analysis model is constructed by using a framework based on the fusion of finite element theory and neural network algorithm. This framework aims to integrate the accuracy of finite element method in structural mechanics analysis and the advantages of neural network algorithm in processing complex nonlinear relationships and adaptive learning.

[0008] For the finite element modeling of the arch foundation, according to its actual geometric shape, it is discretized into multiple three-dimensional solid units, concrete material characteristic parameters, elastic modulus E c、Poisson's ratio ν c For the rigid skeleton, it is discretized into beam elements or bar elements according to its actual rod arrangement and connection mode. The elastic modulus of steel E s、 Yield strength f y The parameters are determined according to the model specifications of the selected steel materials. In terms of boundary condition setting, accurate simulation is performed based on the actual contact between the arch foundation and the surrounding soil and the connection constraints of the rigid skeleton in the structure.

[0009] The neural network adopts a multi-layer perceptron structure, which includes an input layer, a hidden layer, and an output layer. The number of nodes in the input layer is determined according to the influencing factors considered, including but not limited to the size parameters of the arch foundation, the length L b , Width W b、 Height b , geometric characteristic parameters of the rigid skeleton, rod length L s、 Section size A s , load parameters during construction, dead load P at different construction stages g 、Live load P i And the ambient temperature parameter T e , a total of n parameters, so the number of input layer nodes is n, the number of hidden layer nodes is m through the formula Determine, where p is the number of output layer nodes, output arch foundation concrete stress distribution results and rigid skeleton deformation results, set to 2, through subsequent model training and verification for fine-tuning optimization, the number of output layer nodes is set to 2, corresponding to the output of arch foundation concrete stress distribution and rigid skeleton deformation, the weight initialization of the neural network adopts the random normal distribution initialization method, the weight w ij , where i represents the node number of the previous layer, j represents the node number of the next layer, and the value range is set between [-0.5, 0.5]. The bias term b j The initial value of is set to 0;

[0010] Part of the data of the arch foundation and the rigid skeleton under different working conditions obtained by finite element analysis is used as the training sample input of the neural network, and the corresponding accurate analysis results are used as the target output for training. During the training process, the back propagation algorithm is used to adjust the weights and bias items of the neural network to minimize the error between the predicted output and the target output. The error function uses the mean square error MSE function, and its formula is:

[0011]

[0012] Among them, N is the number of training samples, y k is the target output of the kth training sample, The predicted output of the neural network for the kth training sample is continuously iterated until the preset training stop condition is reached;

[0013] S2, deformation impact analysis: input the actual load conditions and real-time data of ambient temperature changes during construction and operation into the trained collaborative analysis model to obtain the deformation data of the rigid skeleton at different times, including the axial deformation δ of each rod s , bending deformationθ s Through the finite element analysis module inside the model, the stress changes of each unit inside the arch foundation concrete are calculated according to the deformation of the rigid skeleton. In the specific calculation process, the elastic mechanics constitutive equation is used to calculate the stress of the concrete unit. For the plane stress problem, the normal stress σ of the concrete unit x , σ y and shear stress τ x The calculation formula for y is as follows:

[0014]

[0015] τ xy =G c γ xy

[0016] Among them, ε x , ε y is the linear strain of the concrete unit in the x and y directions, is the shear modulus of concrete, γ xy is the shear strain of the concrete unit;

[0017] Input the real-time data into the collaborative analysis model to obtain the deformation data of the arch foundation at different times. Based on the finite element analysis, according to the deformation of the arch foundation, calculate the internal force changes of each member of the rigid skeleton, including axial force and bending moment. For the calculation of the internal force of the member, according to the basic principles of structural mechanics, for the member that bears the combined action of axial force and bending moment, its axial force can be calculated through the node force balance equation, and the bending moment can be calculated through the relationship between the bending deformation and the bending stiffness of the member;

[0018] S3, implementation of crack control measures: According to the stress state of the arch foundation concrete during the coordinated deformation process, the concrete stress distribution obtained by the collaborative analysis model is used to adjust the concrete mix ratio and determine the adjustment range of cement dosage C. The maximum allowable tensile stress of concrete during the coordinated deformation process is assumed to be σ allow Through the test, the early strength development curve and shrinkage rate curve of concrete under different cement dosage were determined. According to the principle of elastic mechanics, there is a certain proportional relationship between the tensile strength and compressive strength of concrete. Generally, the tensile strength is 1 / 10 to 1 / 20 of the compressive strength. Assuming that the tensile strength of concrete in this project is 1 / 15 of the compressive strength, and the design compressive strength of the arch foundation concrete is known to be f c , then the design tensile strength of concrete is When the collaborative analysis model predicts the tensile stress σ at a certain part of the concrete t Close to or exceed When reducing the amount of cement, the ratio is reduced according to σ t and The difference between the cement content and the influence of cement on the strength and shrinkage of concrete is determined. It has been found through tests that for every 10% reduction in cement dosage, the early strength of concrete decreases by 5% and the shrinkage rate decreases by 3%. The specific proportion of reducing cement dosage can be determined based on the size of Δσ.

[0019] Aggregates are strictly screened and evaluated based on their particle size distribution, crushing value, and needle-like content, and the particle size distribution coefficient D is set. p , requiring D p Between 0.4 and 0.6, the crush value Q c Should be less than 15%, needle-like content A f Should be less than 10%;

[0020] According to the performance requirements of concrete in the process of coordinated deformation, different types of admixtures are added. When it is necessary to reduce the hydration heat of concrete, a retarder is added. The amount of retarder is A h According to the cement content C of concrete and the expected construction temperature T s Determine, assuming that the ratio coefficient of the amount of retarder added to the amount of cement is k h , and the proportionality coefficient with the construction temperature is k t , then A h =k h C+k t T s ;

[0021] According to the temperature field distribution of the arch foundation and the rigid frame during the coordinated deformation, effective temperature control measures are set, and the temperature field distribution T in different construction and operation stages is predicted through the collaborative analysis model. e For cooling inside the concrete, cooling water pipes are used for cooling. The layout density of cooling water pipes is ρ w According to the volume of concrete V c and the expected maximum temperature rise ΔT e Determine, assuming that the ratio coefficient between the cooling water pipe layout density and the concrete volume is k v , and the proportionality coefficient to the maximum temperature rise is k ΔT , then w =k v V c +k ΔT ΔT e , cover the concrete surface with insulation material, the thickness of the insulation material is h i According to the ambient temperature T e and concrete surface temperature Ts The difference between the thermal conductivity of the insulation material and i Determine, and assume that the proportional coefficient between the thickness of the insulation material and the temperature difference is The proportionality coefficient with thermal conductivity is k λ ,but

[0022] According to the stress distribution of the arch foundation concrete and the stress state of the rigid frame obtained by analysis, the reinforcement of the arch foundation is optimized and the layout of the steel bars is determined. According to the stress distribution of the concrete, the steel bars are arranged preferentially in the stress concentration areas and the areas where tensile stress may occur, the connection between the arch foundation and the rigid frame, and the bottom edge of the arch foundation, and the number of steel bars N is determined. r and specifications, assuming that the maximum tensile stress of a certain part of the concrete during the coordinated deformation process is σ t , the yield strength of the steel bar is f y According to the principle of joint work between steel bars and concrete, the tensile stress that the steel bars can bear is at least σ t 80%, then the number of steel bars N r It can be calculated by the following formula:

[0023]

[0024] Among them, N r Indicates the number of steel bars required to be arranged at a certain part of the abutment foundation, σ t It indicates the maximum tensile stress of a certain part of concrete during the coordinated deformation process, A c refers to the cross-sectional area of ​​the concrete at that location, f y Represents the yield strength of the steel bar.

[0025] Furthermore, in the step of establishing the collaborative analysis model of the arch seat foundation and the rigid skeleton, for the finite element part, when the arch seat foundation is constructed by layered casting, each layer of concrete should be discretized separately, and each layer of concrete should be regarded as an independent entity unit for modeling. The connection between the layers of concrete is simulated by setting contact units. The parameter setting of the contact unit should be determined according to the bonding condition between the two adjacent layers of concrete in the actual construction. If a special adhesive is used to bond the two adjacent layers of concrete, the bonding strength and shear modulus parameters of the adhesive can be determined by experiment, and they can be input into the finite element model as relevant parameters of the contact unit to more accurately simulate the actual structural state of the arch seat foundation during the layered casting construction process, thereby improving the simulation accuracy of the collaborative analysis model for the collaborative deformation relationship between the arch seat foundation and the rigid skeleton. In this process, the elastic modulus E of the concrete material characteristic parameter c、 Poisson's ratio ν c According to the measurement method, the load parameter P during the construction process is obtained. g P lAlso remains unchanged, the ambient temperature parameter T e The same remains unchanged, ensuring the consistency and accuracy of the model.

[0026] Furthermore, in the step of establishing the collaborative analysis model of the arch seat foundation and the rigid skeleton, for the neural network part, during the training process, in order to improve the generalization ability and prediction accuracy of the model, a data enhancement training method is adopted to perform random transformation operations on the original training samples, including but not limited to random scaling, rotation, and translation operations on the input data to generate new training samples. For the input arch seat foundation size parameters, its length is randomly scaled by 5% to 15% on the original basis, the width is rotated by 10° to 30°, and the height is translated by 5 to 15 cm. These transformed samples are then trained together with the original samples as training data. Through this data enhancement training method, the neural network can better adapt to the collaborative deformation analysis of the arch seat foundation and the rigid skeleton under different working conditions, reduce the occurrence of dimensional fitting, and improve the prediction accuracy of the model. When performing these operations, the number of input layer nodes n, the number of hidden layer nodes m, the number of output layer nodes p, and the weight w of the neural network are ij and the bias term b j The parameters remain unchanged as set to ensure the standardization and effectiveness of model training.

[0027] Furthermore, in the step of analyzing the deformation influence relationship through the collaborative analysis model, when analyzing the influence of the rigid skeleton deformation on the stress distribution of the arch seat foundation concrete, its torsional deformation ω should also be considered. s The influence of torsional deformation on the stress distribution of the arch foundation concrete is calculated in the following way: According to the principle of structural mechanics, the additional stress component caused by torsional deformation is determined. For the rigid skeleton members with circular cross-section, the shear stress τ caused by torsional deformation is t By formula Calculate, where T s is the torque, W p The shear stress is used as the initial stress condition and substituted into the stress calculation constitutive equation of the concrete unit to recalculate the stress distribution of the concrete unit, so as to more comprehensively grasp the influence of the deformation of the rigid skeleton on the stress distribution of the arch foundation concrete, determine the parts where stress concentration may occur due to torsional deformation, and provide a more accurate basis for the formulation of subsequent crack control measures. In this process, the elastic modulus E of the concrete material characteristic parameter is c、 Poisson's ratio ν c And the load parameter P during construction g , P l Keep unchanged, the ambient temperature parameter T e This ensures consistency in analysis.

[0028] Furthermore, in the step of analyzing the deformation influence relationship through the collaborative analysis model, when analyzing the reaction of the deformation of the abutment foundation to the stress state of the rigid skeleton, the uneven settlement of the abutment foundation at different construction stages and operation stages should be considered. b The influence of the stress state of the rigid frame, uneven settlement will cause additional bending moment M in the rigid frame members. s and additional axial force F s , for the additional bending moment M s According to the basic principles of structural mechanics, the initial internal force state of the rigid skeleton members when there is no uneven settlement of the abutment foundation is determined, including the initial bending moment M s0 and the initial axial force F s0 , assuming that the bending stiffness of the rigid skeleton member is EI s The length of the beam element is L s , the uneven settlement difference of the abutment foundation at a certain position is Δδ b By establishing the deformation coordination equation of the beam element, the deformation expression related to the uneven settlement can be obtained. Combined with the force balance equation, the additional bending moment M is obtained. s The calculation formula is:

[0029]

[0030] For the additional axial force F s The calculation is also based on the node force balance equation, taking into account the change in rod length ΔL caused by uneven settlement s Assume that the axial stiffness of the rigid skeleton member is EA s According to the geometric relationship and material mechanics, the length change of the rod ΔL can be obtained. s and differential sedimentation δ b The relationship expression is then substituted into the node force balance equation to solve the additional axial force F s The calculation formula is:

[0031]

[0032] Among them, ΔL s The specific calculation of M needs to be determined comprehensively based on the geometric shape of the arch foundation, the uneven settlement distribution, and the layout of the rigid skeleton members. s and F s The influence of the stress state of the rigid skeleton on the concrete skeleton is to have a more comprehensive understanding of the changes in the stress state of the rigid skeleton so as to strengthen it in a targeted manner in the crack control measures. In this process, the concrete material characteristic parameters such as elastic modulus E c , Poisson's ratio ν c And the load parameter P during construction g , Pl Keep unchanged, the ambient temperature parameter T e This ensures consistency in analysis.

[0033] Furthermore, in the step of optimizing the concrete mix ratio, in addition to adjusting the cement dosage according to the stress state of concrete during the coordinated deformation process, the water-cement ratio W / C needs to be finely regulated. Through a large number of experiments, a performance database related to the strength development curve, shrinkage performance curve and impermeability performance curve of concrete under different water-cement ratios is established. The expected performance index set of a key part of concrete during the coordinated deformation process is set as P exp = {P1,P2,…,P n}(where P i It can represent specific performance indicators such as strength, shrinkage, and impermeability. The current water-cement ratio is W / C0, and the corresponding actual performance indicator set is For each performance indicator P i , calculate its adjustment coefficient For the strength index, if the expected strength is The actual strength is The strength adjustment factor

[0034] Comprehensively consider the adjustment coefficients of various performance indicators and determine the total adjustment coefficient K by weighted average. adj , let the weight of the intensity index be w fc , the weight of the shrinkage index is w s , the weight of the impermeability index is w p , then the total adjustment coefficient K adj The calculation formula is:

[0035]

[0036] Then according to the total adjustment factor K adj Adjust the water-cement ratio, the new water-cement ratio W / C nkew =W / C0×K adj Through this fine control of the water-cement ratio, the comprehensive performance of concrete is further optimized, making it better able to resist cracks during the coordinated deformation process while meeting other related performance requirements. In this process, the elastic modulus E of concrete c , Poisson's ratio ν c Material characteristic parameters and load parameters P during construction g , P l Keep unchanged, the ambient temperature parameter T e It also remains unchanged, ensuring the rationality and consistency of the mix ratio adjustment.

[0037] Furthermore, in the step of setting the temperature control measures, when the cooling water pipe is used to cool the concrete interior, in addition to considering the volume V of the concrete c and the expected maximum temperature rise ΔT e To determine the layout density of cooling water pipes ρ w In addition, the diameter d of the cooling water pipe must also be considered. w The cooling efficiency curves of cooling water pipes with different diameters under different concrete volumes and temperatures were established through experiments. The concrete volume is V. c The maximum temperature rise is expected to be ΔT e , the currently selected pipe diameter is d w , the corresponding cooling efficiency is η dw , according to the desired cooling target temperature T target Compared with the expected temperature T when no cooling measures are taken without The difference ΔT goal =T target -T without , and the cooling efficiency η du , calculate the required cooling water pipe layout length L w , the calculation formula is:

[0038]

[0039] Assume that the cooling water pipes are arranged in parallel with equal spacing, and the spacing between two adjacent cooling water pipes is s. w , the effective area A for arranging cooling water pipes can be calculated based on the cross-sectional shape and size of the concrete. eff , according to the cooling water pipe layout length L w and effective area A eff , determine the number of cooling water pipes N w , the calculation formula is:

[0040]

[0041] By taking the pipe diameter factor into consideration, the layout parameters of the cooling water pipe can be set more accurately to ensure the expected cooling effect inside the concrete, effectively reduce the temperature stress, and prevent cracks caused by temperature changes. In this process, the elastic modulus E of the concrete material characteristic parameter c、 Poisson's ratio ν c And the load parameter P during construction g , P i Keep unchanged, the ambient temperature parameter T e It also remains unchanged, ensuring the rationality and consistency of the temperature control measures.

[0042] Furthermore, in the reinforcement design step, after determining the layout, quantity and specifications of the steel bars, the anchorage length L of the steel bars must also be considered. a The influence on the reinforcement effect is based on the strength grade of concrete f c The type of steel bar and the stress environment in which the steel bar is located are determined by combining relevant standard formulas with test data to determine the minimum anchorage length requirements for steel bars in different situations. For HRB400 steel bars in the tension zone and concrete strength grade C30, according to the standard formula combined with test verification, the minimum anchorage length L a min It may be 35d, where d is the diameter of the steel bar. In the actual reinforcement design, it should be ensured that the anchorage length of the steel bar is not less than this minimum anchorage length, and the anchorage length can be appropriately increased according to the specific stress conditions to improve the cooperative working ability of the steel bar and concrete, so that the steel bar can more effectively bear the tensile stress generated by the concrete in the process of cooperative deformation and prevent cracks due to tension. In this process, the elastic modulus E of the concrete material characteristic parameter is c、 Poisson's ratio ν c And the load parameter P during construction g , P l Keep unchanged, the ambient temperature parameter T e It also remains unchanged, ensuring the rationality and consistency of the reinforcement design.

[0043] Furthermore, in the step of controlling the construction process, during the pouring of the arch foundation concrete, in addition to controlling the pouring speed v c and pouring height h c In addition, the vibration method of concrete needs to be strictly regulated, and the appropriate vibration equipment and vibration time t should be determined according to the slump S of concrete and the aggregate particle size D. v0 For concrete with large slump and small aggregate size, insert vibrator is used, and the vibration time is set between 15 and 30 seconds. For concrete with small slump and large aggregate size, flat vibrator is used, and the vibration time can be set between 20 and 40 seconds. By reasonably selecting vibration equipment and strictly controlling vibration time, the density of concrete during pouring is ensured, the quality of concrete is improved, and the cracks are better resisted in the process of coordinated work between the arch foundation and the rigid skeleton, ensuring the structural integrity of the project. In this process, the elastic modulus E of the concrete material characteristic parameter is c、 Poisson's ratio ν c And the load parameter P during construction g , P i Keep unchanged, the ambient temperature parameter T e It also remains unchanged, ensuring the rationality and consistency of construction process control.

[0044] Compared with the existing technology, the method for controlling cracks in large-volume concrete of arch foundation of large-span rigid skeleton arch bridge has the following beneficial effects:

[0045] 1. The present invention realizes the accurate prediction and optimization of crack control of large-volume concrete in the arch seat foundation of large-span rigid skeleton arch bridge by constructing a collaborative analysis model based on the fusion of finite element theory and neural network algorithm. The model can comprehensively consider the collaborative deformation relationship between the arch seat foundation and the rigid skeleton, as well as the actual load conditions and ambient temperature changes during construction and operation, so as to accurately predict the stress distribution of concrete and the deformation of the rigid skeleton, significantly improve the accuracy and efficiency of crack control, and provide strong technical support for engineering practice.

[0046] 2. The present invention is highly targeted and practical by adjusting the concrete mix ratio, adding admixtures, setting temperature control measures and optimizing the reinforcement design. The concrete stress distribution and rigid frame deformation obtained by the collaborative analysis model can be used to adjust the concrete mix ratio and cement dosage in a targeted manner, and admixtures can be added to reduce the adverse effects of hydration heat. At the same time, effective temperature control measures can be set according to the temperature field distribution. In addition, by optimizing the reinforcement design, the bearing capacity and crack resistance of the arch seat foundation can be further improved. The comprehensive application of these measures effectively reduces the crack risk of large-volume concrete in the arch seat foundation of large-span rigid frame arch bridges, and improves the overall quality and safety of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0048] Figure 1 Operational flow chart of the method for controlling cracks in large-volume concrete of the arch foundation of a large-span rigid skeleton arch bridge. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Embodiment 1

[0051] This embodiment describes a large-scale cross-river arch bridge construction project, in which a large-span rigid skeleton arch bridge design is adopted. Since the bridge site is located in an area with a wide river surface and turbulent water flow, extremely high requirements are placed on the stability and durability of the arch seat foundation. In order to ensure the safety and durability of the arch bridge during construction and operation, it is decided to adopt the above-mentioned crack control method.

[0052] The geometric shape data and material property data of the arch bridge are collected, including the size parameters of the arch foundation, the geometric characteristic parameters of the rigid skeleton, the load parameters during the construction process, and the ambient temperature parameters. Based on the collected data, the finite element theory and the neural network algorithm are used to build a collaborative analysis model. The arch foundation is discretized into multiple three-dimensional solid units, and the elastic modulus parameters of the concrete material are set. The rigid skeleton is discretized into beam units or rod units, and the elastic modulus of the steel is determined according to the selected steel model. At the same time, reasonable boundary conditions are set to simulate the actual contact between the arch foundation and the surrounding soil and the connection constraints of the rigid skeleton in the structure. Part of the data of the arch foundation and the rigid skeleton under different working conditions obtained by finite element analysis is used as the training sample input of the neural network, and the corresponding precise analysis results are used as the target output for training. Through continuous iterative training, the weights and bias terms of the neural network are adjusted to minimize the error between the predicted output and the target output. The error function adopts the mean square error MSE function, and its formula is:

[0053]

[0054] Among them, N is the number of training samples, y k is the target output of the kth training sample, The predicted output of the neural network for the kth training sample is continuously iterated through training until the preset training stop condition is reached.

[0055] During the construction process, the actual data of construction load and ambient temperature are input in real time. Through the trained collaborative analysis model, the deformation data of the rigid skeleton at different times are obtained, including the axial deformation and bending deformation of each rod. At the same time, the deformation data of the arch foundation at different times are obtained. The finite element analysis module inside the collaborative analysis model is used to calculate the stress changes of each unit inside the concrete and the internal force changes of the rods according to the deformation of the rigid skeleton and the arch foundation. The positive stress σ x , σ y and shear stress τ x The calculation formula for y is as follows:

[0056]

[0057] τ xy =G c γ xy

[0058] Among them, ε x , ε y is the linear strain of the concrete unit in the x and y directions, is the shear modulus of concrete, γ xy The shear strain of the concrete unit can be used to timely discover potential deformation and stress concentration areas, providing a basis for the implementation of subsequent crack control measures.

[0059] According to the stress distribution of concrete predicted by the collaborative analysis model, the mix ratio of concrete is adjusted. When it is predicted that the tensile stress of a certain part of the concrete is close to or exceeds the design allowable value, the cement dosage is reduced to reduce the tensile stress of the concrete. The reduction ratio is determined based on the difference between the tensile stress and the design allowable value and the influence of the cement dosage on the strength and shrinkage of the concrete. Aggregates are strictly screened to ensure that the particle size distribution, crushing value, and needle-like content of the aggregates meet the requirements. The particle size distribution coefficient of the aggregate is set between 0.4 and 0.6, the crushing value is less than 15%, and the needle-like content is less than 10%. Different types of admixtures are added according to the performance requirements of concrete in the collaborative deformation process. When it is necessary to reduce the hydration heat of concrete, add an appropriate amount of retarder. The amount of retarder added is determined according to the cement content of concrete and the expected construction temperature. According to the temperature field distribution in different construction stages and operation stages predicted by the collaborative analysis model, effective temperature control measures are set. For cooling inside the concrete, insulation materials are covered on the concrete surface to reduce the temperature gradient. The layout density of cooling water pipes and the thickness of insulation materials are determined according to specific circumstances. Based on the analyzed stress distribution of the arch foundation concrete and the stress state of the rigid frame, the reinforcement of the arch foundation is optimized. Steel bars are preferentially arranged at key positions of stress concentration, areas where tensile stress may occur, and at the connection between the arch foundation and the rigid frame. The number and specifications of the required steel bars are calculated based on the principle that steel bars and concrete work together.

[0060] Embodiment 2

[0061] In a highway construction project in a mountainous area, due to the complex terrain and harsh geological conditions, it is necessary to build a large-span rigid skeleton arch bridge to cross the deep valley. The arch bridge not only has to withstand huge traffic loads, but also has to face the influence of temperature changes, rainfall, and earthquakes that are unique to mountainous areas. This places extremely high demands on the stability and crack resistance of the arch foundation.

[0062] The geometric shape data, material property data and geological condition data of the arch bridge are collected. At the same time, the unique environmental factors in mountainous areas, such as the temperature difference between day and night, rainfall intensity, wind direction and speed, are taken into consideration. The finite element theory and neural network algorithm are used, and the principles of geological mechanics and engineering mechanics are combined to construct a collaborative analysis model. The arch base is discretized into multiple three-dimensional solid units, and its interaction with the surrounding soil is considered. The rigid skeleton is discretized into beam units or rod units, and its stiffness and mass distribution are considered. At the same time, reasonable boundary conditions and initial conditions are set according to the collected environmental data. Part of the data obtained by finite element analysis under different working conditions is used as the training sample input of the neural network, and the corresponding precise analysis results are used as the target output for training. Through continuous iterative training, the weights and bias items of the neural network are adjusted to improve the prediction accuracy and generalization ability of the model.

[0063] During the construction process, sensors are used to monitor the actual data of construction load, ambient temperature, rainfall intensity, and groundwater level in real time. At the same time, geological radar or CT scanning technology is used to monitor the interaction between the arch foundation and the surrounding soil. Through the collaborative analysis model, the deformation data of the rigid skeleton and the arch foundation are obtained in real time, including the axial deformation, bending deformation, shear deformation of each rod, and the settlement and tilt deformation of the arch foundation. The finite element analysis module within the collaborative analysis model is used to calculate the stress changes of each unit inside the concrete and the internal force changes of the rods based on the deformation data. The positive stress σ x , σ y and shear stress τ x The calculation formula for y is as follows:

[0064]

[0065] τ xy =G c γ xy

[0066] Among them, ε x , ε y is the linear strain of the concrete unit in the x and y directions, is the shear modulus of concrete, γ xy The shear strain of the concrete unit can be used to timely discover potential deformation and stress concentration areas, providing a basis for subsequent crack control measures.

[0067] According to the prediction results of the collaborative analysis model, the mix ratio of concrete is adjusted. When it is predicted that the tensile stress of a certain part is close to or exceeds the design allowable value, the amount of cement is reduced to reduce the tensile stress of concrete. At the same time, an appropriate amount of fly ash and slag powder admixtures are added to improve the microstructure of concrete and enhance its crack resistance. Aggregates are strictly screened to ensure that the particle size distribution, crushing value, and needle-like content of aggregates meet the requirements. At the same time, the quality control of aggregates is strengthened to avoid the use of aggregates containing impurities or severe weathering. According to the performance requirements of concrete in the unique environment of mountainous areas, appropriate admixtures are selected and their addition amounts are determined, such as adding water reducers to improve the fluidity of concrete, Reduce water consumption, add anti-cracking agent to improve the crack resistance of concrete, add waterproofing agent to improve the waterproof performance of concrete, set effective temperature control measures according to the temperature field distribution predicted by the collaborative analysis model, such as using cooling water pipes for internal cooling, covering the concrete surface with insulation materials to reduce the temperature gradient, using sunshade nets or sprinkler systems to reduce the ambient temperature, and setting up effective drainage systems in view of the frequent rainfall in mountainous areas, such as setting up drainage ditches and water collection wells to drain surface water and groundwater; set up a waterproof layer around the arch foundation to isolate the erosion of the foundation by groundwater, and at the same time, strengthen the waterproof treatment of concrete, such as applying waterproof paint and setting up waterproof membranes;

[0068] According to the prediction results of the collaborative analysis model and engineering experience, the reinforcement design of the arch foundation is optimized. Steel bars are arranged preferentially in stress concentration areas, areas where tensile stress may occur, and key positions where the arch foundation and the rigid frame are connected. At the same time, the influence of the diameter, spacing and arrangement method of the steel bars on the crack resistance of concrete is considered. During the construction process, construction is carried out strictly in accordance with the construction drawings and operating procedures; supervision and inspection of construction quality are strengthened, quality problems in construction are discovered and dealt with in a timely manner, and during the maintenance stage, moisture retention and maintenance of concrete are strengthened to avoid heavy loading or vibration operations before the concrete strength reaches the design requirements.

[0069] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for controlling cracks in large-volume concrete of arch foundation of a large-span rigid skeleton arch bridge, characterized in that: The specific steps of this method are: S1, Establishment of collaborative analysis model: A collaborative analysis model is constructed by using a framework based on the fusion of finite element theory and neural network algorithm. This framework aims to integrate the accuracy of finite element method in structural mechanics analysis and the advantages of neural network algorithm in processing complex nonlinear relationships and adaptive learning. For the finite element modeling of the arch foundation, according to its actual geometric shape, it is discretized into multiple three-dimensional solid units, concrete material characteristic parameters, elastic modulus E c、 Poisson's ratio ν c For the rigid skeleton, it is discretized into beam elements or bar elements according to its actual rod arrangement and connection mode. The elastic modulus of steel E s、 Yield strength f y The parameters are determined according to the model specifications of the selected steel materials. In terms of boundary condition setting, accurate simulation is performed based on the actual contact between the arch foundation and the surrounding soil and the connection constraints of the rigid skeleton in the structure. The neural network adopts a multi-layer perceptron structure, which includes an input layer, a hidden layer, and an output layer. The number of nodes in the input layer is determined according to the influencing factors considered, including but not limited to the size parameters of the arch foundation, the length L b , Width W b、 Height b , geometric characteristic parameters of the rigid skeleton, rod length L s、 Section size A s , load parameters during construction, dead load P at different construction stages g 、Live load P i And the ambient temperature parameter T e , a total of n parameters, so the number of input layer nodes is n, the number of hidden layer nodes is m through the formula Determine, where p is the number of output layer nodes, output arch foundation concrete stress distribution results and rigid skeleton deformation results, set to 2, through subsequent model training and verification for fine-tuning optimization, the number of output layer nodes is set to 2, corresponding to the output of arch foundation concrete stress distribution and rigid skeleton deformation, the weight initialization of the neural network adopts the random normal distribution initialization method, the weight w ij , where i represents the node number of the previous layer, j represents the node number of the next layer, and the value range is set between [-0.5, 0.5]. The bias term b j The initial value of is set to 0; Part of the data of the arch foundation and the rigid skeleton under different working conditions obtained by finite element analysis is used as the training sample input of the neural network, and the corresponding accurate analysis results are used as the target output for training. During the training process, the back propagation algorithm is used to adjust the weights and bias items of the neural network to minimize the error between the predicted output and the target output. The error function uses the mean square error MSE function, and its formula is: Among them, N is the number of training samples, y k is the target output of the kth training sample, The predicted output of the neural network for the kth training sample is continuously iterated until the preset training stop condition is reached; S2, deformation impact analysis: input the actual load conditions and real-time data of ambient temperature changes during construction and operation into the trained collaborative analysis model to obtain the deformation data of the rigid skeleton at different times, including the axial deformation δ of each rod s , bending deformationθ s Through the finite element analysis module inside the model, the stress changes of each unit inside the arch foundation concrete are calculated according to the deformation of the rigid skeleton. In the specific calculation process, the elastic mechanics constitutive equation is used to calculate the stress of the concrete unit. For the plane stress problem, the normal stress σ of the concrete unit x , σ y and shear stress τ x The calculation formula for y is as follows: t xy =G c c xy Among them, ε x , ε y is the linear strain of the concrete unit in the x and y directions, is the shear modulus of concrete, γ xy is the shear strain of the concrete unit; Input the real-time data into the collaborative analysis model to obtain the deformation data of the arch foundation at different times. Based on the finite element analysis, according to the deformation of the arch foundation, calculate the internal force changes of each member of the rigid skeleton, including axial force and bending moment. For the calculation of the internal force of the member, according to the basic principles of structural mechanics, for the member that bears the combined action of axial force and bending moment, its axial force can be calculated through the node force balance equation, and the bending moment can be calculated through the relationship between the bending deformation and the bending stiffness of the member; S3, implementation of crack control measures: According to the stress state of the arch foundation concrete during the coordinated deformation process, the concrete stress distribution obtained by the collaborative analysis model is used to adjust the concrete mix ratio and determine the adjustment range of cement dosage C. The maximum allowable tensile stress of concrete during the coordinated deformation process is assumed to be σ allow Through the test, the early strength development curve and shrinkage rate curve of concrete under different cement dosage were determined. According to the principle of elastic mechanics, there is a certain proportional relationship between the tensile strength and compressive strength of concrete. Generally, the tensile strength is 1 / 10 to 1 / 20 of the compressive strength. Assuming that the tensile strength of concrete in this project is 1 / 15 of the compressive strength, and the design compressive strength of the arch foundation concrete is known to be f c , then the design tensile strength of concrete is When the collaborative analysis model predicts the tensile stress σ at a certain part of the concrete t Close to or exceed When reducing the amount of cement, the ratio is reduced according to σ t and The difference between the cement content and the influence of cement on the strength and shrinkage of concrete is determined. It has been found through tests that for every 10% reduction in cement dosage, the early strength of concrete decreases by 5% and the shrinkage rate decreases by 3%. The specific proportion of reducing cement dosage can be determined based on the size of Δσ. Aggregates are strictly screened and evaluated based on their particle size distribution, crushing value, and needle-like content, and the particle size distribution coefficient D is set. p , requiring D p Between 0.4 and 0.6, the crush value Q c Should be less than 15%, needle-like content A f Should be less than 10%; According to the performance requirements of concrete in the process of coordinated deformation, different types of admixtures are added. When it is necessary to reduce the hydration heat of concrete, a retarder is added. The amount of retarder is A h According to the cement content C of concrete and the expected construction temperature T s Determine, assuming that the ratio coefficient of the amount of retarder added to the amount of cement is k h , and the proportionality coefficient with the construction temperature is k t , then A h =k h C+k t T s ; According to the temperature field distribution of the arch foundation and the rigid frame during the coordinated deformation, effective temperature control measures are set, and the temperature field distribution T in different construction and operation stages is predicted through the collaborative analysis model. e For cooling inside the concrete, cooling water pipes are used for cooling. The layout density of cooling water pipes is ρ w According to the volume of concrete V c and the expected maximum temperature rise ΔT e Determine, assuming that the ratio coefficient between the cooling water pipe layout density and the concrete volume is k v , and the proportionality coefficient to the maximum temperature rise is k ΔT , then w =k v V c +k ΔT ΔT e , cover the concrete surface with insulation material, the thickness of the insulation material is h i According to the ambient temperature T e and concrete surface temperature T s The difference between the thermal conductivity of the insulation material and i Determine, and assume that the proportional coefficient between the thickness of the insulation material and the temperature difference is The proportionality coefficient with thermal conductivity is k λ ,but According to the stress distribution of the arch foundation concrete and the stress state of the rigid frame obtained by analysis, the reinforcement of the arch foundation is optimized and the layout of the steel bars is determined. According to the stress distribution of the concrete, the steel bars are arranged preferentially in the stress concentration areas and the areas where tensile stress may occur, the connection between the arch foundation and the rigid frame, and the bottom edge of the arch foundation, and the number of steel bars N is determined. r and specifications, assuming that the maximum tensile stress of a certain part of the concrete during the coordinated deformation process is σ t , the yield strength of the steel bar is f y According to the principle of joint work between steel bars and concrete, the tensile stress that the steel bars can bear is at least σ t 80%, then the number of steel bars N r It can be calculated by the following formula: Among them, N r Indicates the number of steel bars required to be arranged at a certain part of the abutment foundation, σ t It indicates the maximum tensile stress of a certain part of concrete during the coordinated deformation process, A c refers to the cross-sectional area of ​​the concrete at that location, f y Represents the yield strength of the steel bar.

2. The method for controlling cracks in large-volume concrete of arch base foundation of a large-span rigid skeleton arch bridge according to claim 1 is characterized in that: In the step of establishing the collaborative analysis model of the arch seat foundation and the rigid skeleton, for the finite element part, when the arch seat foundation is constructed by layered casting, each layer of concrete should be discretized separately, and each layer of concrete should be regarded as an independent solid unit for modeling. The connection between the layers of concrete is simulated by setting contact units. The parameter setting of the contact unit should be determined according to the bonding conditions between the two adjacent layers of concrete in actual construction. If a special adhesive is used to bond the two adjacent layers of concrete, the bonding strength and shear modulus parameters of the adhesive are determined by experiments, and they are input into the finite element model as relevant parameters of the contact unit.

3. The method for controlling cracks in large-volume concrete of arch base foundation of a large-span rigid skeleton arch bridge according to claim 1 is characterized in that: In the step of establishing the collaborative analysis model of the arch seat foundation and the rigid frame, for the neural network part, a data enhancement training method is adopted to perform random transformation operations on the original training samples, including but not limited to random scaling, rotation, and translation operations on the input data, to generate new training samples. For the input arch seat foundation size parameters, its length is randomly scaled by 5% to 15% on the original basis, the width is rotated by 10° to 30°, and the height is translated by 5 to 15 cm. Then these transformed samples are used as training data together with the original samples for training.

4. The method for controlling cracks in large-volume concrete of arch base foundation of a large-span rigid skeleton arch bridge according to claim 1 is characterized in that: In the step of analyzing the deformation influence relationship through the collaborative analysis model, when analyzing the influence of the rigid skeleton deformation on the stress distribution of the arch seat foundation concrete, the torsional deformation ω should also be considered. s The influence of torsional deformation on the stress distribution of the arch foundation concrete is calculated in the following way: According to the principle of structural mechanics, the additional stress component caused by torsional deformation is determined. For the rigid skeleton members with circular cross-section, the shear stress τ caused by torsional deformation is t By formula Calculate, where T s is the torque, W p In order to obtain the torsional section modulus, this shear stress is used as the initial stress condition and substituted into the stress calculation constitutive equation of the concrete unit to recalculate the stress distribution of the concrete unit, thereby more comprehensively understanding the influence of the deformation of the rigid skeleton on the stress distribution of the arch foundation concrete and determining the locations where stress concentration may occur due to torsional deformation.

5. The method for controlling cracks in large-volume concrete of arch base foundation of a large-span rigid skeleton arch bridge according to claim 1 is characterized in that: In the step of analyzing the deformation influence relationship through the collaborative analysis model, when analyzing the reaction of the deformation of the abutment foundation to the stress state of the rigid skeleton, the uneven settlement δ of the abutment foundation at different construction stages and operation stages should be considered. b The influence of the stress state of the rigid frame, uneven settlement will cause additional bending moment M in the rigid frame members. s and additional axial force F s , for the additional bending moment M s According to the basic principles of structural mechanics, the initial internal force state of the rigid skeleton members when there is no uneven settlement of the abutment foundation is determined, including the initial bending moment M s0 and the initial axial force F s0 , assuming that the bending stiffness of the rigid skeleton member is EI s The length of the beam element is L s , the uneven settlement difference of the abutment foundation at a certain position is Δδ b By establishing the deformation coordination equation of the beam element, the deformation expression related to the uneven settlement can be obtained. Combined with the force balance equation, the additional bending moment M is obtained. s The calculation formula is: For the additional axial force F s The calculation is also based on the node force balance equation, taking into account the change in rod length ΔL caused by uneven settlement s Assume that the axial stiffness of the rigid skeleton member is EA s According to the geometric relationship and material mechanics, the length change of the rod ΔL can be obtained. s and differential sedimentation δ b The relationship expression is then substituted into the node force balance equation to solve the additional axial force F s The calculation formula is: Where, ΔL s The specific calculation of M needs to be determined comprehensively based on the geometric shape of the arch foundation, the uneven settlement distribution, and the layout of the rigid skeleton members. s and F s The influence of the stress state of the rigid skeleton.

6. The method for controlling cracks in large-volume concrete of arch seat foundation of a large-span rigid skeleton arch bridge according to claim 1 is characterized in that: In the step of optimizing the concrete mix ratio, in addition to adjusting the cement dosage according to the stress state of concrete during the coordinated deformation process, the water-cement ratio W / C needs to be finely regulated. Through a large number of experiments, a performance database related to the strength development curve, shrinkage performance curve and impermeability performance curve of concrete under different water-cement ratios is established. The expected performance index set of a key part of concrete during the coordinated deformation process is set as P exp = {P1,P2,…,P n }, where P i It can represent specific performance indicators of strength, shrinkage, and impermeability. The current water-cement ratio is W / C0, and the corresponding actual performance indicator set is For each performance indicator P i , calculate its adjustment coefficient For the strength index, if the expected strength is The actual strength is The strength adjustment factor Comprehensively consider the adjustment coefficients of various performance indicators and determine the total adjustment coefficient K by weighted average. adj , let the weight of the strength index be The weight of the shrinkage index is w s , the weight of the impermeability index is w p , then the total adjustment coefficient K adj The calculation formula is: Then according to the total adjustment factor K adj Adjust the water-cement ratio, the new water-cement ratio W / C nkew =W / C0×K adj .

7. The method for controlling cracks in large-volume concrete of arch base foundation of a large-span rigid skeleton arch bridge according to claim 1 is characterized in that: In the step of setting temperature control measures, when cooling water pipes are used to cool the interior of concrete, in addition to considering the volume V of the concrete, c and the expected maximum temperature rise ΔT e To determine the layout density of cooling water pipes ρ w In addition, the diameter d of the cooling water pipe must also be considered. w The cooling efficiency curves of cooling water pipes with different diameters under different concrete volumes and temperatures were established through experiments. The concrete volume is V. c The maximum temperature rise is expected to be ΔT e , the currently selected pipe diameter is d w The corresponding cooling efficiency is According to the desired cooling target temperature T target Compared with the expected temperature T when no cooling measures are taken without The difference ΔT goal =T target -T without , and cooling efficiency Calculate the required cooling water pipe layout length L w , the calculation formula is: Assume that the cooling water pipes are arranged in parallel with equal spacing, and the spacing between two adjacent cooling water pipes is s. w , the effective area A for arranging cooling water pipes can be calculated based on the cross-sectional shape and size of the concrete. eff , according to the cooling water pipe layout length L w and effective area A eff , determine the number of cooling water pipes N w , the calculation formula is: By taking the pipe diameter factor into comprehensive consideration, the layout parameters of the cooling water pipe can be set more accurately.

8. The method for controlling cracks in large-volume concrete of arch base foundation of a large-span rigid skeleton arch bridge according to claim 1 is characterized in that: In the reinforcement design step, after determining the layout, quantity and specifications of the steel bars, the anchorage length L of the steel bars must also be considered. a The influence on the reinforcement effect is based on the strength grade of concrete f c The type of steel bar and the stress environment in which the steel bar is located are determined by combining relevant standard formulas with test data to determine the minimum anchorage length requirements for steel bars in different situations. For HRB400 steel bars in the tension zone and concrete strength grade C30, according to the standard formula combined with test verification, the minimum anchorage length It may be 35d, where d is the diameter of the steel bar. In the actual reinforcement design, it should be ensured that the anchorage length of the steel bar is not less than this minimum anchorage length, and the anchorage length can be appropriately increased according to the specific stress conditions to improve the collaborative working ability of the steel bar and concrete.

9. The method for controlling cracks in large-volume concrete of arch base foundation of a large-span rigid skeleton arch bridge according to claim 1, characterized in that: In the step of controlling the construction process, during the pouring of the arch foundation concrete, in addition to controlling the pouring speed v c and pouring height h c In addition, the vibration method of concrete needs to be strictly regulated, and the vibration equipment and vibration time should be determined according to the slump S of concrete and the aggregate particle size D. For concrete with large slump and small aggregate size, use an insert vibrator and set the vibration time between 15 and 30 seconds. For concrete with small slump and large aggregate size, use a flat vibrator and set the vibration time between 20 and 40 seconds.

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