Calculation method for stiffness of composite beam connected by high-strength bolts

Abstract

The present invention relates to the technical field of bridge construction, and discloses a method for calculating the stiffness of a composite beam connected by high-strength bolts, which includes the following steps. When calculating, the most unfavorable loads that may occur in the normal service stage and the construction stage should be considered. Calculate the standard value of the most unfavorable load combination on the composite beam, and at the same time set the mid-span displacement determination value. The present invention analyzes the stress state of the steel-concrete interface under various loads, can accurately capture the critical points of interface shear stress and friction failure, adopts different stiffness calculation formulas, can accurately simulate the non-linear variation law of the equivalent stiffness of the composite beam with the load, and at the same time this design method systematically considers various influencing factors, simulates the non-linear mechanism of the bolt connection area, can give relatively accurate displacement values, and takes into account the economic evaluation, and is a relatively comprehensive design and analysis method for composite beams.

Description

Technical Field

[0001] The present invention relates to the field of bridge construction, and more specifically, it relates to a method for calculating the stiffness of a composite beam connected by high-strength bolts. Background Art

[0002] Under the background of the sustainable development of the industry, bridge construction is gradually developing towards the direction of prefabrication and industrialization. The construction of the deck concrete slab of composite bridges has always been carried out by in-situ casting, with a large amount of on-site wet work and a long construction period, making it impossible to achieve complete prefabrication, which is a bottleneck in realizing prefabricated construction. Developing composite beams connected by high-strength bolts can not only realize the on-site assembly and disassembly of concrete, but also avoid the welding defects caused by stud welding.

[0003] At present, the current specifications for the design of composite structures are all for in-situ cast composite beams connected by studs, and there are no clear regulations for precast slab composite beams connected by bolts;

[0004] Deflection deformation control is of great significance to the design and construction of bolted composite beams in bridges, which is jointly determined by the steel beam size, bolt diameter, number of bolts and pre-tension force. The connection method and force transmission mechanism of bolted composite beams and stud composite beams are very different. If the friction force of the pre-tensioned bolts is overcome and the bolt shank has not yet contacted the bolt hole wall, then the bolt temporarily exits the work, and the composite beam degrades into a state of variable stiffness beam, and the range of the low-stiffness section will change with the load. At this time, the composite beam still has a large bearing capacity, but the influence of friction overcoming and interface slip on the flexural stiffness cannot be ignored. Summary of the Invention

[0005] The present invention provides a method for calculating the stiffness of a composite beam connected by high-strength bolts, which solves the technical problem in the related art that the deflection of a variable stiffness composite beam cannot be calculated.

[0006] The present invention provides a method for calculating the stiffness of a composite beam connected by high-strength bolts, including the following steps:

[0007] S100: In the service stage and the construction stage, when the most unfavorable load appears, calculate the standard value of the most unfavorable load combination on the composite beam, and at the same time set the mid-span displacement determination value ;

[0008] S200: Determine the population of steel beam geometric parameters , the population of bolt shear connector parameters , assign multiple common values to each parameter in each population, and , Sort according to economic parameters; assign multiple common values to each variable, then there are multiple combination schemes between the first group of variables and the second group of variables , and then output the economic parameters of each scheme and ;

[0009] S300: Given the parametric population, calculate the yield judgment condition of the composite beam under the parametric population ;

[0010] If , return to S300, let ;

[0011] If , enter S400;

[0012] Wherein is the standard value of the bending moment;

[0013] S400: Calculate the longitudinal shear force when the composite beam with stud connections degrades from an equal - stiffness beam to a variable - stiffness beam ;

[0014] S500: Calculate the external load when the composite beam with stud connections degrades from an equal - stiffness beam to a variable - stiffness beam ;

[0015] S600: Use the equivalent stiffness of the reduced composite beam to calculate the mid - span deflection under the action of the load standard value in segments ;

[0016] S610: Determine the interface state:

[0017] If , the composite beam is in the state of an equal - stiffness beam throughout the loading process;

[0018] If , the composite beam degrades from an equal - stiffness beam to a variable - stiffness beam under the action of the load;

[0019] S620: Judge according to the deflection criterion:

[0020] The mid - span deflection is greater than the mid - span displacement judgment value, , then return to S200, let ;

[0021] The mid - span deflection is less than the mid - span displacement judgment value, , the design is completed.

[0022] Furthermore, the load combination standard value and the bending moment standard value are as follows:

[0023] ;

[0024] ;

[0025] Wherein, is the load combination standard value, is the standard value of bending moment, is the thickness of the concrete slab, is the unit weight of concrete, is the additional permanent load, is the additional dead load, is the live load for use, is the span length of the beam;

[0026] In step S100, the following steps are included:

[0027] S110: Load identification. First, it is necessary to identify various permanent loads and possible temporary loads acting on the composite beam structure, including self-weight of the structure, additional permanent load, live load, wind load, and temperature load;

[0028] S120: Load combination. According to different load cases and load combination codes, the identified permanent loads and temporary loads are combined to form a series of different load case combinations. The load combination is:

[0029] ;

[0030] Among them, represents the standard value of the th load, is its corresponding combination coefficient, and the combination coefficients for different load types are determined according to the code;

[0031] S130: Load internal force calculation. For each load case combination, calculate the corresponding internal force effects, including bending moment, shear force, and axial force;

[0032] S140: Limit state check. Compare the calculated internal force effects with the bearing capacity of the structure to check whether the requirements of relevant limit states are met, including the ultimate bearing capacity limit state and the serviceability limit state;

[0033] S150: Identification of adverse load combinations. For different design requirements, identify the corresponding most adverse load combinations;

[0034] S160: Setting the mid-span displacement judgment value. According to the code requirements or the actual engineering needs, set the allowable mid-span displacement judgment value of the composite beam under normal service conditions .

[0035] Furthermore, according to the numerical size sorting of and , respectively assign values to , ;

[0036] ;

[0037] ;

[0038] Wherein , .

[0039] Furthermore, in step S200, according to the engineering conditions, the span of the composite beam and the thickness of the concrete slab are set as fixed values;

[0040] The height , width , thickness of the steel web , thickness of the steel flange plate and the yield strength of the steel constitute the first group of variables :

[0041] ;

[0042] The number of shear keys of the friction-type high-strength bolts in the shear span is , the diameter of the friction-type high-strength bolts in the shear span is , and the pre-tightening force of the bolts is constitute the second group of variables :

[0043] ;

[0044] It is also necessary to calculate the economic cost corresponding to the geometric parameters Calculate the economic cost corresponding to the connector parameters , and list them according to all and combinations, and calculate the total economic cost and for each combination, including the following: :

[0045] 1) Calculate the economic cost corresponding to the geometric parameters ; ;

[0046] is related to the consumption of concrete and steel and the construction difficulty factors, and is estimated using the following empirical formula:

[0047] ;

[0048] Wherein, and are the consumption of concrete and steel respectively, and are the construction difficulty coefficients of concrete and steel structures respectively, , , , is the corresponding unit cost coefficient;

[0049] 2) Calculate the connector parameters The corresponding economic cost ;

[0050] is related to the quantity and type of high-strength bolt connectors and is estimated using the following formula:

[0051] ;

[0052] where is the number of high-strength bolts, is the diameter of a single high-strength bolt cost, is the installation additional cost coefficient;

[0053] 3) List all and combination cases, and calculate the total economic cost for each combination:

[0054] ;

[0055] According to the size of, sort and number all combination schemes, and the scheme with lower economic cost is ranked in the front and the number is relatively smaller.

[0056] Furthermore, in step S300, set the initial values of the combined population and . The material of the stiffness reduction calculation method conforms to Hooke's law. Set the yield discrimination condition to determine that all materials have not reached the yield stress;

[0057] 1) Calculate the yield moment generated by the cross-section :

[0058] ;

[0059] where is the yield strength of the steel, is the equivalent stiffness, is the geometric centroid distance between the steel beam and the concrete slab;

[0060] 2) Calculate the equivalent stiffness and axial stiffness of the composite cross-section:

[0061] ;

[0062] ;

[0063] ;

[0064] ;

[0065] Among them, is the yield moment generated by the cross-section under boundary conditions, is the yield strength of the steel, is the equivalent stiffness, is the axial stiffness, is the equivalent stiffness of the composite section, is the elastic modulus of the steel, is the moment of inertia of the steel, is the elastic modulus of the concrete, is the moment of inertia of the concrete slab, is the equivalent axial stiffness of the composite section, is the cross-sectional area of the concrete slab, is the cross-sectional area of the steel;

[0066] In step S300, the initial values of the combined population and are:

[0067] ;

[0068] .

[0069] Furthermore, in step S400, when the friction force at the steel-concrete interface is sufficient to overcome the longitudinal shear force and all bolts are in the friction stage, the shear stiffness of each bolt is constant at , which is determined by the push-out test, and the composite beam is a beam with equal stiffness;

[0070] If the load continues to increase and the friction force is not sufficient to overcome the shear force, the bolts overcome the friction sequentially from the support end to the mid-span, and the shear stiffness of the bolt degrades to zero. The composite beam degrades to a state of a variable-stiffness beam, and the variable-stiffness beam has a non-stiffness region with a length of at the support end;

[0071] The implementation steps are as follows:

[0072] S410: When the friction force at the steel-concrete interface is large enough, all connecting bolts are in the friction stage, that is, they only bear shear force without bearing bending moment;

[0073] At this time, the shear stiffness of each bolt is a constant, and its value needs to be determined by the push-out test;

[0074] The composite beam is regarded as a beam with equal stiffness in this case;

[0075] S420: As the load continues to increase, when the interfacial frictional force is insufficient to bear the shear force, the bolts will overcome the frictional force one by one from the support end to the mid-span;

[0076] For the bolts that have overcome the friction, their shear stiffness will degrade to 0;

[0077] The composite beam is regarded as a variable stiffness beam in this case;

[0078] S430: In a certain length range near the support of the variable stiffness beam, since the bolts no longer provide shear stiffness, it is equivalent to a zero stiffness region, and the length is denoted as ;

[0079] S440: When there is shear force at the interface, the longitudinal shear force on the steel-concrete interface when overcoming the friction is:

[0080] ;

[0081] ;

[0082] ;

[0083] Among them, is the number of shear keys of the friction-type high-strength bolts in the shear span, is the diameter of the friction-type high-strength bolts in the shear span, is the shear stiffness of each bolt, and are both intermediate parameters used to calculate the longitudinal shear force distribution on the steel-concrete interface in the shear-connected hybrid components, is a combined parameter related to the parameters of the component stiffness and the connector stiffness, reflecting the change rate of the shear force distribution along the axial direction of the component, is another combined parameter related to the component stiffness and the connector parameters, reflecting the overall magnitude of the shear force in the component, is the intensity of the uniformly distributed load, is the distance from the support to the considered section, is the shear span length, is the natural constant.

[0084] Furthermore, in step S500, according to the load form, calculate the load when the first bolt at the support end overcomes the friction:

[0085] ;

[0086] Among them is the friction coefficient, is the interfacial shear stress;

[0087] If , where , according to the principle of minimum potential energy, the stiffness reduction coefficient of the composite beam considering the interface slip effect is taken as ;

[0088] ;

[0089] If , where , according to the principle of minimum potential energy, the stiffness reduction coefficient of the composite beam considering both the interface slip and friction overcoming effects is taken as ;

[0090] ;

[0091] The calculation steps are as follows:

[0092] S510: List the geometric and material parameters of the composite beam: is the shear span length, is the diameter of the friction-type high-strength bolts in the shear span, is the number of shear keys of the friction-type high-strength bolts in the shear span, is the shear stiffness of each bolt, is the equivalent stiffness of the composite section, is the equivalent axial stiffness of the composite section, is the geometric centroid distance between the steel beam and the concrete slab, is the friction coefficient, is the interface shear stress;

[0093] S520: Calculate the auxiliary parameters and :

[0094] ;

[0095] ;

[0096] S530: According to the ultimate state when the first bolt at the support end overcomes the friction, list the expression of the interface shear stress :

[0097] ;

[0098] S540: Substitute into the expression of , and solve for :

[0099] ;

[0100] S550: Simplify and organize to obtain an equation about :

[0101] ;

[0102] S560: Solve the equation to obtain the critical uniform load when the first bolt at the support end overcomes friction. By calculating the critical load :

[0103] When , an equal - stiffness beam model can be adopted;

[0104] When , it is necessary to convert to a variable - stiffness beam model and consider the influence of bolt failure.

[0105] Further, in step S600, the implementation process of this step is as follows:

[0106] 1) Determine the interface state

[0107] According to the result of interface state analysis, judge whether the interface is in the full - friction stage or the partial / full - failure state;

[0108] ;

[0109] Among them, is the first composite beam stiffness reduction coefficient, is the shear - lag coefficient of the equal - stiffness beam;

[0110] ;

[0111] Among them, is the second composite beam stiffness reduction coefficient, is the shear - lag coefficient of the variable - stiffness beam;

[0112] 2) Calculate the basic parameters

[0113] In the full - friction stage, calculate the equivalent:

[0114] ;

[0115] Among them , are the elastic modulus and moment of inertia of concrete respectively, , are the elastic modulus and moment of inertia of the steel beam respectively;

[0116] In the partial / full - failure state, it is necessary to determine the number of failed bolts , and calculate the interface shear deformation angle γ;

[0117] 3) Calculate the equivalent stiffness in segments

[0118] In the full friction stage, the equivalent stiffness is ;

[0119] In the partial failure stage, the equivalent stiffness , and is calculated according to the following formula:

[0120] ;

[0121] ;

[0122] where is the correction coefficient, is the shear shape coefficient, is the shear modulus of the steel beam material, is the cross-sectional area, is the net distance of the steel-concrete interface, is the number of failed bolts, is the total number of bolts, is the span length;

[0123] In the full failure stage, the equivalent stiffness , and is calculated according to the following formula:

[0124] ;

[0125] The above formulas illustrate that bolt failure and interface shear slip affect the overall stiffness of the composite beam. By calculating and reducing the equivalent stiffness in segments, the deformation performance of the composite beam at each load stage is simulated;

[0126] 4) Obtain the equivalent stiffness

[0127] Based on the results of calculating the equivalent stiffness in segments, obtain the equivalent stiffness corresponding to the current load stage , or ;

[0128] 5) Establish a deflection calculation model

[0129] Equivalent the composite beam to a simply supported beam and adopt the basic formula in mechanics of materials:

[0130] In the full friction stage:

[0131] ;

[0132] In the partial failure stage:

[0133] ;

[0134] In the full failure stage:

[0135] ;

[0136] Wherein is the uniformly distributed load applied externally, is the span length of the beam;

[0137] 6) Revised calculation

[0138] For practical engineering problems, a correction factor is introduced, and the beam-end restraint conditions and the load distribution form are considered:

[0139] ;

[0140] Wherein is the correction factor, which depends on the restraint conditions and the load distribution;

[0141] Among them, , , is the current equivalent stiffness provided by the above steps, corresponding to , or corresponding to .

[0142] The present invention also provides a stiffness calculation system for a composite beam connected by high-strength bolts, which is used for the steps in the stiffness calculation method of the composite beam connected by high-strength bolts as described above, and includes:

[0143] Load calculation module: This module is used to calculate the most unfavorable load combination in the normal service stage and the construction stage, and set the mid-span displacement determination value ;

[0144] Geometric parameter input module: This module is used to input the geometric parameters of the composite beam, including the span , the thickness of the concrete slab , the section height of the H-shaped steel beam , the width , the thickness of the steel web , the thickness of the steel flange plate and the yield strength of the steel , and these parameters constitute the first group of variables ;

[0145] Connector parameter input module: This module is used to input the parameters of the high-strength bolt connectors, including the number of friction-type high-strength bolts in the shear span, the diameter and the pre-tightening force , and these parameters constitute the second group of variables ;

[0146] Economic evaluation module: According to and For different combinations, calculate the economic parameters of various schemes and , and sort and number the combined schemes according to the magnitudes of these two parameters;

[0147] Material constitutive module: This module sets the constitutive model of the material. The material conforms to Hooke's law and determines the yield criterion;

[0148] Interface state analysis module: According to the magnitude of the load, analyze whether the frictional force at the steel-concrete interface is sufficient to overcome the longitudinal shear force, and determine whether each bolt is in the frictional stage or the failure state, corresponding to the cases of equal-stiffness beams or variable-stiffness beams;

[0149] Critical load calculation module: Calculate the critical load when the first bolt at the support end overcomes friction ;

[0150] Stiffness reduction module: According to the interface state, perform segmented calculation and reduction of the equivalent stiffness of the composite beam;

[0151] Displacement calculation module: Use the reduced equivalent stiffness to calculate the mid-span deflection of the composite beam under the action of the load .

[0152] The present invention provides a storage medium storing non-temporary computer-readable instructions for executing one or more steps in the method for calculating the stiffness of a composite beam with high-strength bolt connections described above.

[0153] The beneficial effects of the present invention are as follows:

[0154] The present invention analyzes the stress state at the steel-concrete interface under various loads, can accurately capture the critical points of interface shear stress and frictional force failure, adopts different stiffness calculation formulas, can accurately simulate the non-linear variation law of the equivalent stiffness of the composite beam with the load, and at the same time, this design method systematically considers various influencing factors, simulates the non-linear mechanism in the bolt connection area, can give relatively accurate displacement values, and takes into account the economic evaluation, and is a relatively comprehensive design and analysis method for composite beams. BRIEF DESCRIPTION OF THE DRAWINGS

[0155] Figure 1 is a flowchart of a method for calculating the stiffness of a composite beam with high-strength bolt connections proposed by the present invention;

[0156] Figure 2 is a structural schematic diagram of the vertical section of a cast-in-place composite beam proposed by the present invention;

[0157] Figure 3 is a structural schematic diagram of a cast-in-place composite beam as an equal-stiffness beam proposed by the present invention;

[0158] Figure 4 This is a schematic diagram of the cast-in-place composite beam degenerating into a variable stiffness beam proposed in the present invention. Detailed implementation manners

[0159] Now, the subject matter described herein will be discussed with reference to exemplary implementation manners. It should be understood that discussing these implementation manners is only to enable those skilled in the art to better understand and thus implement the subject matter described herein. Without departing from the scope of protection of the content of this specification, changes can be made to the functions and arrangements of the elements discussed. Each example can omit, substitute, or add various processes or components as needed. Additionally, the features described relative to some examples can also be combined in other examples.

[0160] Refer to Figures 1-4 As shown, a method for calculating the stiffness of a composite beam connected by high-strength bolts includes the following steps:

[0161] S100: When calculating, the most unfavorable loads that may occur during the normal use stage and the construction stage should be considered. Calculate the standard value of the most unfavorable load combination on the composite beam, and at the same time set the mid-span displacement determination value ;

[0162] ;

[0163] ;

[0164] Wherein: is the standard value of the load combination, is the standard value of the bending moment, is the thickness of the concrete slab, is the unit weight of concrete, is the additional permanent load, is the additional dead load, is the live load for use, is the span length of the beam;

[0165] In step S100, the following steps are also included:

[0166] S110: Load identification: First, it is necessary to identify various permanent loads and possible temporary loads acting on the composite beam structure, including but not limited to the self-weight of the structure, additional permanent loads (such as paving loads), live loads (such as vehicle loads), wind loads, temperature loads, etc.

[0167] S120: Load combination: According to different load conditions and load combination codes, combine the identified permanent loads and temporary loads to form a series of different load condition combinations. The general form of the mathematical expression for the load combination is:

[0168] ;

[0169] Among them, represents the standard value of the th type of load, is its corresponding combination coefficient, and the combination coefficients for different load types are determined according to the code;

[0170] S130: Load internal force calculation: For each load case combination, calculate the corresponding internal force effects, including bending moment, shear force, axial force, etc.;

[0171] S140: Limit state check: Compare the calculated internal force effects with the bearing capacity of the structure to check whether the relevant limit state requirements are met, such as the ultimate bearing capacity limit state, serviceability limit state, etc.;

[0172] S150: Identification of adverse load combinations: For different design requirements (such as bearing capacity design, deformation control under normal use, etc.), identify the corresponding most adverse load combinations;

[0173] S160: Setting the mid-span displacement judgment value: According to the code requirements or engineering actual needs, set the allowable mid-span displacement judgment value of the composite beam under normal use conditions ;

[0174] In addition to the above steps, it is also necessary to determine the standard values or characteristic values of various loads. For example, for the live load, the characteristic value may be obtained through statistical fitting, and its mathematical expression is as follows:

[0175] ;

[0176] Among them, is the characteristic value of the live load, is the mean value, is the coefficient of variation, is the confidence level coefficient.

[0177] S200: Determine the population of geometric parameters of the steel beam , the population of parameters of the bolt shear connectors , assign multiple common values to each parameter in each population, and , sort them according to the economic parameters;

[0178] According to the engineering conditions, set the span of the composite beam and the thickness of the concrete slab as fixed values;

[0179] The section height of the H-shaped steel beam, the width , the thickness of the steel web , the thickness of the steel flange plate and the yield strength of steel are the first group of variables :

[0180] ;

[0181] The number of shear-resistant high-strength bolts with frictional type in a shear span , diameter , bolt pre-tightening force are the second group of variables :

[0182] ;

[0183] Assign multiple common values to each variable, then the combination and the combination both have multiple combination schemes;

[0184] Furthermore, output the economic parameters of each scheme and ;

[0185] According to and sort by the numerical size, and respectively assign values to , assign values, , ;

[0186] ;

[0187] ;

[0188] In step S200, the user needs to input the following parameters:

[0189] Span : The calculated span of the composite beam;

[0190] Concrete slab thickness : The thickness of the upper concrete slab of the composite beam;

[0191] Section height of the H-shaped steel beam : The section height of the steel beam part of the composite beam;

[0192] Width of the steel beam flange : The width of the steel beam flange of the composite beam;

[0193] Thickness of the steel web : The thickness of the steel web of the composite beam;

[0194] Thickness of the steel flange plate : The thickness of the steel flange plate of the composite beam;

[0195] Yield strength of steel : Yield strength of the steel for the composite beam;

[0196] These parameters can be input in the form of a user interface or a parameter file and form the first set of variables , namely:

[0197] ;

[0198] During the implementation process, reasonable value ranges and increments can be set for each parameter to facilitate subsequent parameter combination and optimization calculations;

[0199] At the same time, it is also necessary to check the validity of the input parameters to ensure that they meet the requirements of relevant design specifications and engineering practices;

[0200] For example, for the flange width and the web thickness , the following mathematical expressions can be given as inspection conditions according to the requirements of the overall stability of the cross-section:

[0201] ;

[0202] Among them, is the limit value given by the specification or experience;

[0203] Through the input of parameters in this step, accurate geometric parameter input can be provided for subsequent structural analysis and optimization design, thus ensuring the accuracy and reliability of the calculation results.

[0204] In step S200, the main function is to obtain the relevant parameters of the high-strength bolt connectors in the steel-concrete connection area of the composite beam, and these parameters will directly affect the overall performance of the entire structure;

[0205] It also includes the following parameters that need to be input by the user: the number of friction-type high-strength bolts in the shear span : refers to the total number of high-strength bolts used in a shear span (i.e., the area between two adjacent supports); the diameter of the high-strength bolt : the nominal diameter of the high-strength bolt; the pre-tightening force of the high-strength bolt : the pre-tightening tension applied to the high-strength bolt; these parameters form the second set of variables , namely:

[0206] ;

[0207] When implementing this module, reasonable value ranges and increments need to be set for the above parameters to meet the engineering requirements and facilitate subsequent optimization calculations. At the same time, it is also necessary to check the validity of the input parameters to ensure compliance with relevant specifications and engineering practices.

[0208] For example, for the pre-tightening force of high-strength bolts , the following mathematical inspection conditions can be given according to the requirements of the bolt tensile strength:

[0209] ;

[0210] Among them, is the tensile strength of the bolt material, is the cross-sectional area of the bolt.

[0211] In addition, this module also needs to consider the influence of the number and arrangement of high-strength bolts in different shear spans to ensure sufficient shear transfer capacity and deformation coordination.

[0212] Through the implementation of this module, accurate connector parameter input can be provided for subsequent structural analysis and optimization design, which is crucial for ensuring the overall performance of the composite beam.

[0213] In step S200, the following steps can also be included:

[0214] Calculate geometric parameters The corresponding economic cost :

[0215] It is usually related to factors such as the consumption of concrete and steel, and the construction difficulty. The following empirical formula can be used for estimation:

[0216] ;

[0217] Among them, and are the consumption of concrete and steel respectively; and are the construction difficulty coefficients of concrete and steel structures respectively; , , , are the corresponding unit cost coefficients.

[0218] Calculate the economic cost corresponding to the connector parameters : :

[0219] It is mainly related to the number and type of high-strength bolt connectors, and the following formula can be used for estimation:

[0220] ;

[0221] Among them, is the number of high-strength bolts, is the diameter of a single high-strength bolt cost, is the additional cost coefficient for installation, etc.

[0222] List all and combinations, and calculate the total economic cost for each combination :

[0223] ;

[0224] According to the magnitude, sort and number all combination schemes. The schemes with lower economic costs are ranked in the front and have relatively smaller numbers.

[0225] Through the above steps, the economy of various composite beam schemes can be systematically evaluated, providing valuable information for subsequent optimization;

[0226] It should be noted that the calculation of economic cost in actual projects is usually more complex and may require the introduction of more influencing factors. The above formula is only a simplified example.

[0227] S300: Given the parameter population, calculate the yield judgment condition of the composite beam under this condition ;

[0228] Specifically, in the example, the initial values of the composite population and are , ;

[0229] The assumption of the stiffness reduction calculation method is that the material is linearly elastic and conforms to Hooke's law. Therefore, it is necessary to set the yield discrimination condition to ensure that all materials have not reached the yield stress;

[0230] If , return to S300 and let ;

[0231] If , enter S400;

[0232] Specifically, step S300 is the starting step of a loop for stiffness reduction calculation. In this step, the values of some parameters are initialized, such as the population size and the number of iterations, etc.

[0233] Before entering the loop, some important assumptions are made:

[0234] The material follows linear elasticity and conforms to Hooke's law; it is necessary to set the yield criterion to ensure that all materials have not reached the yield stress;

[0235] The main calculation steps during the loop:

[0236] 1. Calculate the yield moment generated by the cross-section :

[0237] ;

[0238] where is the yield strength of the steel,[[]] is the equivalent stiffness,[[]] is the distance between the geometric centroids of the steel beam and the concrete slab;

[0239] 2. Calculate the equivalent stiffness and the axial stiffness :

[0240] ;

[0241] ;

[0242] ;

[0243] ;

[0244] where , are the elastic moduli of the steel bar and the concrete respectively,[[]] , are the moments of inertia of the steel bar and the concrete respectively,[[]] , are the cross-sectional areas of the steel bar and the concrete respectively;

[0245] Specifically, is the yield moment generated by the cross-section under the boundary conditions,[[]] is the yield strength of the steel,[[]] is the equivalent stiffness,[[]] is the distance between the geometric centroids of the steel beam and the concrete slab,[[]] is the equivalent stiffness of the composite cross-section,[[]] is the elastic modulus of the steel,[[]] is the moment of inertia of the steel,[[]] is the elastic modulus of the concrete,[[]] is the moment of inertia of the concrete slab,[[]] is the equivalent axial stiffness of the composite cross-section,[[]] is the cross-sectional area of the concrete slab,[[]] is the cross-sectional area of the steel;

[0246] Compare the calculated with the standard value :

[0247] If , it indicates that the material has not yielded. Return to S300 and increase the number of iterations , perform the next iterative calculation;

[0248] If , it indicates yielding, and the program enters S400 to perform corresponding processing, such as margin adjustment, etc.;

[0249] Through continuous iterative calculations until the convergence condition is met, the final and relationship is obtained, thus completing the stiffness reduction calculation.

[0250] S400: Calculate the longitudinal shear force ;

[0251] When the steel-concrete interface friction force is sufficient to overcome the longitudinal shear force and all bolts are in the friction stage, the shear stiffness of each bolt is constant at , which is determined by the push-out test. The composite beam is an equal-stiffness beam, as shown in Appendix Figure 3 ;

[0252] If the load continues to increase and the friction force is insufficient to overcome the shear force, the bolts overcome the friction successively from the support end to the mid-span, and the shear stiffness of the bolt degenerates to zero, and the composite beam degenerates to the state of a variable-stiffness beam, as shown in Appendix Figure 4 ;

[0253] The variable-stiffness beam has a zero-stiffness region with a length of at the support end;

[0254] The longitudinal shear force on the steel-concrete interface when overcoming the friction is:

[0255] ;

[0256] ;

[0257] ;

[0258] Among them, is the number of shear keys of friction-type high-strength bolts in the shear span, is the diameter of friction-type high-strength bolts in the shear span, is the shear stiffness of each bolt, and are both intermediate parameters used to calculate the longitudinal shear force distribution on the steel-concrete interface in shear-connected hybrid components, is a combined parameter related to parameters such as the stiffness of the component and the stiffness of the connector, reflecting the change rate of the shear force distribution along the axial direction of the component, is another combined parameter related to the stiffness of the component and the connector parameters, reflecting the overall magnitude of the shear force in the component, is the intensity of the uniformly distributed load, is the distance from the support to the considered section, is the shear span length, is the natural constant;

[0259] In step S400, the specific implementation steps are as follows:

[0260] S410: When the friction force at the steel-concrete interface is large enough, all connecting bolts are in the friction stage, that is, they only bear shear force without bearing bending moment;

[0261] At this time, the shear stiffness of each bolt is a constant, and its value needs to be determined through a push-out test;

[0262] The composite beam is regarded as an equal-stiffness beam in this case;

[0263] S420: As the load continues to increase, when the interface friction force is not enough to bear the shear force, the bolts will overcome the friction force one by one from the support end to the mid-span;

[0264] For the bolts that have overcome the friction, their shear stiffness will degrade to 0;

[0265] The composite beam is regarded as a variable-stiffness beam in this case;

[0266] S430: In a certain length range near the support of the variable-stiffness beam, since the bolts no longer provide shear stiffness, it is equivalent to a zero-stiffness region, and the length is denoted as ;

[0267] S440: When there is shear force at the interface, its distribution can be calculated according to the following formula:

[0268] ;

[0269] ;

[0270] ;

[0271] where is the number of shear keys of high-strength friction-type bolts in the shear span, is the diameter of high-strength friction-type bolts in the shear span, is the shear stiffness of each bolt, and are both intermediate parameters used to calculate the longitudinal shear force distribution on the steel-concrete interface in the shear connection hybrid member, is a combined parameter related to parameters such as the stiffness of the member and the stiffness of the connector, reflecting the change rate of the shear force distribution along the axial direction of the member, is another combined parameter related to the stiffness of the component and the parameters of the connection member, reflecting the overall magnitude of the shear force in the component. is the intensity of the uniformly distributed load. is the distance from the support to the section under consideration. is the shear span length. is the natural constant.

[0272] S500: The external load when the composite beam with stud connections degrades from a beam with equal stiffness to a beam with variable stiffness. ;

[0273] Specifically, according to the load form, calculate the load when the first bolt at the support end overcomes the friction. :

[0274] ;

[0275] where is the friction coefficient, is the interfacial shear stress;

[0276] In this example, the uniformly distributed load is taken as an example:

[0277] If , according to the principle of minimum potential energy, the stiffness reduction coefficient of the composite beam considering the interfacial slip effect is taken as , where ;

[0278] ;

[0279] If , according to the principle of minimum potential energy, the stiffness reduction coefficient of the composite beam considering both the interfacial slip and the friction overcoming effect is taken as , where ;

[0280] ;

[0281] Specifically, the calculation steps are as follows:

[0282] 1. List the geometric parameters and material parameters of the composite beam: is the shear span length, is the diameter of the friction-type high-strength bolts in the shear span, is the number of shear keys of the friction-type high-strength bolts in the shear span, is the shear stiffness of each bolt, is the equivalent stiffness of the composite section, is the equivalent axial stiffness of the composite section, is the distance between the geometric centroids of the steel beam and the concrete slab, is the friction coefficient, is the interfacial shear stress;

[0283] 2. Calculate auxiliary parameters and :

[0284] ;

[0285] ;

[0286] 3. Write the expression of the interfacial shear stress according to the ultimate state when the first bolt at the support end overcomes friction :

[0287] ;

[0288] 4. Substitute into the expression of and solve for :

[0289] ;

[0290] 5. Simplify and organize to obtain the equation about :

[0291] ;

[0292] 6. Solve the equation to obtain the critical uniform load when the first bolt at the support end overcomes friction , and by calculating the critical load , this model provides an important basis for the overall structural analysis;

[0293] When , the equivalent stiffness beam model with equal stiffness can be adopted;

[0294] When , it is necessary to convert to the variable stiffness beam model and consider the influence of bolt failure;

[0295] This segmented modeling method can accurately simulate the stress-strain behavior of the actual structure;

[0296] S600: Calculate the mid-span deflection under the action of the load standard value in segments using the equivalent stiffness of the composite beam after reduction ;

[0297] S610: Determine the interface state;

[0298] S611: If , the composite beam is in the state of an equal stiffness beam throughout the load application process;

[0299] ;

[0300] Among them, is the stiffness reduction coefficient of the first composite beam, is the shear lag coefficient of the beam with equal stiffness;

[0301] S612: If the composite beam degenerates from a beam with equal stiffness to a beam with variable stiffness under the action of load;

[0302] ;

[0303] Among them, is the stiffness reduction coefficient of the second composite beam, the shear lag coefficient of the beam with variable stiffness;

[0304] S620: Determine according to the deflection criterion;

[0305] S621: If the mid-span deflection is greater than the mid-span displacement determination value, return to S200, and let ;

[0306] S622: If the mid-span deflection is less than the mid-span displacement determination value, the design is completed.

[0307] In step S600, the implementation process of this step is as follows:

[0308] 1. Determine the interface state

[0309] According to the result of the interface state analysis, judge whether the interface is in the full friction stage or the partial / full failure state.

[0310] 2. Calculate the basic parameters

[0311] In the full friction stage, calculate the equivalent:

[0312] ;

[0313] Among them and are the elastic modulus and moment of inertia of concrete respectively, and are the elastic modulus and moment of inertia of the steel beam respectively;

[0314] In the partial / full failure state, it is necessary to determine the number of failed bolts and calculate the interface shear deformation angle γ;

[0315] 3. Calculate the equivalent stiffness in segments

[0316] In the full friction stage, the equivalent stiffness is ;

[0317] In the partial failure stage, the equivalent stiffness , calculated according to the following formula:

[0318] ;

[0319] ;

[0320] where is the correction coefficient, is the shear shape coefficient, is the shear modulus of the steel beam material, is the cross-sectional area, is the net distance of the steel-concrete interface, is the number of failed bolts, is the total number of bolts, is the span length;

[0321] In the complete failure stage, the equivalent stiffness , calculated according to the following formula:

[0322] ;

[0323] The above formula reflects the influence of bolt failure and interface shear slip on the overall stiffness of the composite beam;

[0324] By calculating and reducing the equivalent stiffness in segments, this module can accurately simulate the deformation performance of the composite beam in each load stage and lay a foundation for subsequent structural analysis;

[0325] 4. Obtain the equivalent stiffness

[0326] Obtain the equivalent stiffness corresponding to the current load stage according to the above , or ;

[0327] 5. Establish a deflection calculation model

[0328] Equivalent the composite beam to a simply supported beam and adopt the basic formula in mechanics of materials:

[0329] In the complete friction stage:

[0330] ;

[0331] In the partial failure stage:

[0332] ;

[0333] In the complete failure stage:

[0334] ;

[0335] where is the uniformly distributed load applied externally, is the span length of the beam;

[0336] 6. Revised calculation

[0337] For actual engineering problems, correction factors may need to be introduced to consider the effects of beam end restraint conditions, load distribution forms, etc.:

[0338] ;

[0339] wherein is the correction factor, which depends on the restraint conditions and load distribution;

[0340] The key parameters in this step include:

[0341] wherein, , , is the current equivalent stiffness provided by the above steps, corresponding to , or corresponding to ;

[0342] By reasonably using the equivalent stiffness and the formulas of mechanics of materials, this module can calculate the actual deflection values of the composite beam at each load stage, providing a basis for structural design and safety assessment. This module is closely dependent on the calculation results of the previous two modules.

[0343] According to the above method for calculating the stiffness of a composite beam connected by high-strength bolts, a system for calculating the stiffness of a composite beam connected by high-strength bolts is also proposed, including:

[0344] Load calculation module: This module is used to calculate the most unfavorable load combinations in the normal service stage and the construction stage, and set the mid-span displacement determination value ;

[0345] Geometric parameter input module: This module is used to input the geometric parameters of the composite beam, including the span , the thickness of the concrete slab , the section height of the H-shaped steel beam , the width , the thickness of the steel web , the thickness of the steel flange plate and the yield strength of the steel , and these parameters form the first set of variables ;

[0346] Connector parameter input module: This module is used to input the parameters of the high-strength bolt connectors, including the number of friction-type high-strength bolts within the shear span , the diameter and the pre-tightening force These parameters constitute a second set of variables ;

[0347] Economic evaluation module: According to and different combinations, calculate the economic parameters of various schemes and , and sort and number the combined schemes according to the magnitudes of these two parameters;

[0348] Material constitutive module: This module sets the constitutive model of the material, assumes the material is linearly elastic, conforms to Hooke's law, and determines the yield criterion;

[0349] Interface state analysis module: According to the magnitude of the load, analyze whether the friction force at the steel-concrete interface is sufficient to overcome the longitudinal shear force, and determine whether each bolt is in the friction stage or the failure state, corresponding to the cases of equal-stiffness beams or variable-stiffness beams;

[0350] Critical load calculation module: Calculate the critical load when the first bolt at the support end overcomes the friction ;

[0351] Stiffness reduction module: According to the interface state, perform piecewise calculation and reduction on the equivalent stiffness of the composite beam;

[0352] Displacement calculation module: Use the reduced equivalent stiffness to calculate the mid-span deflection of the composite beam under the action of the load .

[0353] At least one embodiment of the present disclosure provides a storage medium storing non-transitory computer-readable instructions for executing one or more steps in the method for calculating the stiffness of a composite beam connected by high-strength bolts described above.

[0354] The computer program can be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with other hardware or as part of other hardware, but it can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims shall not be construed as limiting the scope.

[0355] The above has described the embodiments of this embodiment, but this embodiment is not limited to the above specific implementation manners. The above specific implementation manners are merely illustrative and not restrictive. Under the inspiration of this embodiment, those of ordinary skill in the art can also make many forms, all of which fall within the protection scope of this embodiment.

Claims

1. A method for calculating the stiffness of a composite beam connected by high-strength bolts, characterized in that: The following steps are involved: S100: During the use and construction phases, when the most unfavorable load occurs, the standard value of the most unfavorable load combination on the composite beam is calculated, and the mid-span displacement judgment value is set at the same time. ; S200: Determine the population of geometric parameters of steel beams , bolt shear connector parameter population , assign multiple common values ​​to each parameter in each population, and , Sort by economic parameters; Assign multiple common values ​​to each variable, then the first group of variables And the second set of variables There are multiple combination schemes, and then the economic parameters of each scheme are output and ; S300: given a parameter population, calculating the yield judgment condition of the composite beam under the parameter population; like , return to S300, and set ; like , enter S400; in is the standard value of bending moment, is the yield moment produced by the cross section; S400: Calculation of longitudinal shear forces in stud-connected composite beams when they degenerate from uniform stiffness beams to variable stiffness beams ; S500: Calculation of external loads when a composite beam with stud connections degenerates from a beam of uniform stiffness to a beam of variable stiffness ; S600: Use the equivalent stiffness of the composite beam after reduction to calculate the mid-span deflection under the load standard value in sections ; The specific steps are as follows: Determine the interface status: According to the results of the interface state analysis, it is determined whether the interface is in the full friction stage or partial / complete failure state; ； in, is the stiffness reduction factor of the first composite beam, is the shear retention coefficient of the beam with uniform stiffness; ； in, is the stiffness reduction factor of the second composite beam, Shear retention coefficient of variable stiffness beam; Calculate basic parameters: In the complete friction stage, the calculation is equivalent to: ； in , are the elastic modulus and moment of inertia of concrete, , are the elastic modulus and moment of inertia of the steel beam respectively; Partial / complete failure, need to determine the number of failed bolts , and calculate the interface shear deformation angle γ; Calculate the equivalent stiffness segment by segment: In the complete friction stage, the equivalent stiffness is ; Partial failure stage, equivalent stiffness , calculated according to the following formula: ； ； in is the correction factor, is the shear shape coefficient, is the shear modulus of the steel beam material, is the cross-sectional area, is the steel-concrete interface clearance, is the number of failed bolts, is the total number of bolts, is the span length; Complete failure stage, equivalent stiffness , calculated according to the following formula: ； The above formula describes the effect of bolt failure and interface shear slip on the overall stiffness of the composite beam. By calculating and reducing the equivalent stiffness in sections, the deformation performance of the composite beam at each load stage is simulated. Get the equivalent stiffness: According to the results of the segmented calculation of equivalent stiffness, the equivalent stiffness corresponding to the current load stage is obtained. , , ; Establish the deflection calculation model: The composite beam is equivalent to a simply supported beam, and the basic formula in material mechanics is used: During the full friction phase: ； During the partial failure phase: ； During the complete failure phase: ； in is an external uniformly distributed load, is the beam span length; Correction calculation: For practical engineering problems, the correction coefficient is introduced, and the beam end constraint conditions and load distribution form are considered: ； in is the correction factor, which depends on the constraints and load distribution; in, , , is the current equivalent stiffness provided by the above steps, correspond , or correspond .

2. The method for calculating the stiffness of a composite beam connected by high-strength bolts according to claim 1, characterized in that: The standard values ​​of load combinations and bending moments are as follows: ； ； in, is the standard value of load combination, is the standard value of bending moment, is the concrete slab thickness, is the concrete bulk density, is the additional permanent load, For additional dead load, To use live load, is the span length of the beam; In step S100, the following steps are included: S110: Load identification, first of all, it is necessary to identify various permanent loads and possible temporary loads acting on the composite beam structure, including structural deadweight, additional permanent loads, live loads, wind loads, and temperature loads; S120: Load combination. According to different load conditions and load combination specifications, the identified permanent loads and temporary loads are combined to form a series of different load condition combinations. The load combinations are: ； in, Indicates The standard value of the load, The corresponding combination coefficients are determined according to the specifications for different load types; S130: Load internal force calculation, for each load condition combination, calculate the corresponding internal force effects, including bending moment, shear force, and axial force; S140: Limit state check, compare the calculated internal force effect with the bearing capacity of the structure to check whether the requirements of the relevant limit states are met, including the bearing capacity limit state and the serviceability limit state; S150: Identification of unfavorable load combinations: for different design requirements, identify the corresponding most unfavorable load combinations; S160: Setting the mid-span displacement judgment value. According to the specification requirements or actual project needs, set the allowable mid-span displacement judgment value of the composite beam under normal use conditions. .

3. The method for calculating the stiffness of a composite beam connected by high-strength bolts according to claim 2, characterized in that: according to and Sort by the numerical size, respectively , Assignment; ； ； in , ; in and are the height and width of the H-beam section, is the steel web thickness, is the steel flange thickness and is the yield strength of steel; in is the number of shear keys of friction type high-strength bolts in the shear span, It is the diameter of the friction type high-strength bolt in the shear span.

4. The method for calculating the stiffness of a composite beam connected by high-strength bolts according to claim 3, characterized in that: In step S200, the span of the composite beam is set according to the engineering conditions. and concrete slab thickness is a fixed value; The height of the H-beam section ,width , steel web thickness , Steel flange thickness and steel yield strength The first set of variables : ； The number of shear keys of the friction type high-strength bolts in the shear span is , the diameter of the friction type high strength bolt in the shear span is , the bolt preload is The second set of variables : ； It is also necessary to calculate the geometric parameters The corresponding economic cost Calculate connector parameters The corresponding economic cost , and according to all and List the combinations and calculate the total economic cost for each combination , including the following: 1) Calculate geometric parameters The corresponding economic cost ; It is related to the amount of concrete and steel used and the difficulty of construction, and is estimated using the following empirical formula: ； in, and are the amounts of concrete and steel, respectively. and are the construction difficulty coefficients of concrete and steel structures, respectively. , , , is the corresponding unit cost coefficient; 2) Calculate the connection parameters The corresponding economic cost ; It is related to the number and type of high-strength bolt connections and is estimated using the following formula: ； in, is the number of high-strength bolts, Diameter The cost of a single high-strength bolt is Add a cost factor for installation; 3) All and List the combinations and calculate the total economic cost for each combination : ； according to All the combination plans are sorted and numbered according to their size. Plans with lower economic costs are ranked at the front and have relatively smaller numbers.

5. The method for calculating the stiffness of a composite beam connected by high-strength bolts according to claim 4, characterized in that: In step S300, set the combined population and The initial value of the material, the stiffness reduction calculation method, conforms to Hooke's law, sets the yield judgment condition, and determines that all materials have not yet reached the yield stress; 1) Calculate the yield moment of the cross section : ； in is the yield strength of steel, is the equivalent stiffness, is the geometric centroid distance between the steel beam and the concrete slab; 2) Calculate the equivalent stiffness of the mixed section and axial stiffness : ； ； ； ； in, is the yield moment of the cross section under boundary conditions, is the yield strength of steel, is the equivalent stiffness, is the axial stiffness, is the equivalent stiffness of the mixed section, is the elastic modulus of steel, is the moment of inertia of steel, is the elastic modulus of concrete, is the moment of inertia of the concrete slab, is the equivalent axial stiffness of the hybrid section, is the cross-sectional area of ​​the concrete slab, is the cross-sectional area of ​​the steel; In step S300, the combined population and The initial value of is: ； 。 6. The method for calculating the stiffness of a composite beam connected by high-strength bolts according to claim 5, characterized in that: In step S400, when the friction force at the steel-concrete interface is sufficient to overcome the longitudinal shear force, all bolts are in the friction stage, and the shear stiffness of each bolt is constant. , this parameter is determined by the push-out test, and the composite beam is a beam of equal stiffness; If the load continues to increase and the friction force is insufficient to overcome the shear force, the bolts overcome the friction from the support end to the mid-span, and the shear stiffness of the bolts degenerates to zero. The composite beam degenerates to a variable stiffness beam. The variable stiffness beam has a length of The stiffness-free region; The implementation steps are as follows: S410: When the friction force at the steel-concrete interface is large enough, all connecting bolts are in the friction stage, that is, they only bear shear force but not bending moment; At this time, the shear stiffness of each bolt is a constant, and its value needs to be determined through push-out tests; The composite beam is considered as a beam of equal stiffness in this case; S420: As the load continues to increase, when the interface friction is insufficient to bear the shear force, the bolts will overcome the friction one by one from the support end to the mid-span; For bolts that have overcome friction, their shear stiffness will degenerate to 0; The composite beam is considered as a variable stiffness beam in this case; S430: Within a certain length range near the support, the variable stiffness beam is equivalent to a non-stiffness area because the bolts no longer provide shear stiffness. The length is recorded as ; S440: When shear exists at the interface When the friction is overcome, the longitudinal shear force on the steel-concrete interface is: ； ； ； in, is the number of shear keys of the friction type high-strength bolts in the shear span, is the diameter of the friction type high-strength bolt in the shear span, is the shear stiffness of each bolt, and They are intermediate parameters used to calculate the longitudinal shear force distribution on the steel-concrete interface in shear-connected composite members. It is a combined parameter related to the stiffness of the component and the stiffness of the connector, reflecting the rate of change of the shear force distribution along the axial direction of the component. It is another combined parameter related to the stiffness of the component and the parameters of the connector, reflecting the overall magnitude of the shear force in the component. is the uniformly distributed load strength, is the distance from the support to the considered section, is the shear span length, is a natural constant.

7. The method for calculating the stiffness of a composite beam connected by high-strength bolts according to claim 6, characterized in that: In step S500, according to the load form, the load required for the first bolt at the end of the support to overcome the friction is calculated. : ； in is the friction coefficient, is the interface shear stress; like ,in According to the principle of minimum potential energy, the stiffness reduction factor of the composite beam considering the interface slip effect is ; ； like ,in According to the principle of minimum potential energy, the stiffness reduction coefficient of the composite beam considering both the interface slip and friction overcoming effect is ; ； The calculation steps are as follows: S510: List the geometric parameters and material parameters of the composite beam: is the shear span length, is the diameter of the friction type high-strength bolt in the shear span, is the number of shear keys of the friction type high-strength bolts in the shear span, is the shear stiffness of each bolt, is the equivalent stiffness of the mixed section, is the equivalent axial stiffness of the hybrid section, is the geometric centroid distance between the steel beam and the concrete slab, is the friction coefficient, is the interface shear stress; S520: Calculate auxiliary parameters and : ； ； S530: List the interface shear stress based on the limit state when the first bolt at the support end overcomes friction The expression is: ； S540: Substitution The expression of : ； S550: Simplify and organize to get about The equation is: ； S560: Solve the equation to obtain the critical uniformly distributed load required for the first bolt at the support end to overcome friction , by calculating the critical load : when When , the equal stiffness beam model can be used; when It is necessary to convert to a variable stiffness beam model and consider the influence of bolt failure.

8. A system for calculating the stiffness of a composite beam connected by high-strength bolts, used to execute the steps in the method for calculating the stiffness of a composite beam connected by high-strength bolts as claimed in any one of claims 1 to 7, characterized in that: include: Load calculation module: This module is used to calculate the most unfavorable load combination during normal use and construction, and to set the mid-span displacement determination value. ; Geometric parameter input module: This module is used to input the geometric parameters of the composite beam, including the span , Concrete slab thickness , H-beam section height ,width , steel web thickness , Steel flange thickness and steel yield strength , these parameters constitute the first set of variables ; Connection parameter input module: This module is used to input the parameters of high-strength bolt connections, including the number of friction-type high-strength bolts in the shear span ,diameter and preload , these parameters constitute the second set of variables ; Economic evaluation module: according to and Calculate the economic parameters of various schemes and , and sort and number the combination schemes according to the size of these two parameters; Material constitutive module: This module sets the constitutive model of the material, the material complies with Hooke's law, and determines the yield criterion; Interface state analysis module: According to the load size, analyze whether the friction force of the steel-concrete interface is sufficient to overcome the longitudinal shear force, and judge whether each bolt is in the friction stage or failure state, corresponding to the situation of equal stiffness beam or variable stiffness beam; Critical load calculation module: Calculates the critical load required for the first bolt at the support end to overcome friction ; Stiffness reduction module: According to the interface state, the equivalent stiffness of the composite beam is calculated and reduced in sections; Displacement calculation module: Use the reduced equivalent stiffness to calculate the mid-span deflection of the composite beam under load .

9. A storage medium, characterized in that: Non-transitory computer-readable instructions are stored, which are used to execute the steps in the method for calculating the stiffness of a composite beam connected by high-strength bolts as described in any one of claims 1-7.

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