A rapid design method for frame truss riveting structure

Abstract

The present application relates to a kind of frame truss riveting structure quick design method, comprising the following steps: (1) establishing standard multi-span beam finite element model, respectively to the combination of different longitudinal girders and cross frame is calculated with the way of finite element support coefficient c;(2) support coefficient c value under different frame truss combination is stored in database;(3) given a group of combination form frame truss riveting structure, corresponding support coefficient c value in database is called to calculate the axial compression bearing capacity of the given frame truss combination form riveting structure;(4) for a variety of possible frame truss combination form, iteration optimization is carried out, i.e. it is calculated using step (3), and the optimal frame truss combination form is obtained from the calculation result.

Description

TECHNICAL FIELD

[0001] The application relates to a quick design method of a frame truss riveting structure and belongs to the field of structural design. BACKGROUND

[0002] A general method for calculating the axial compression bearing capacity of a frame truss riveting cabin body first calculates the horizontal support stiffness provided by a cross frame, then calculates the support coefficient of the cross frame to a longitudinal truss, and further obtains the bearing capacity of the longitudinal truss, and finally obtains the axial compression bearing capacity of the frame truss riveting structure by the finite width method. The support coefficient is usually calculated by an empirical formula and only the bending stiffness of the cross frame is considered, and the torsional stiffness of the cross frame is not considered. When the sectional area of the cross frame increases to a certain extent, the influence of the bending stiffness of the cross frame on the support coefficient will become weaker and weaker, but actually the support effect of the cross frame on the longitudinal truss is obviously improved, which can improve the axial compression bearing capacity of the longitudinal truss. The reason is that the support effect of the torsional stiffness of the cross frame is not considered. The support coefficient of the cross frame to the longitudinal truss can be solved by establishing a local model by the finite element method, and the support effect of the bending stiffness and the torsional stiffness of the cross frame on the axial compression bearing capacity of the longitudinal truss is considered. By combining different longitudinal trusses and cross frames, the support coefficient database can be formed by the finite element method in advance, and the corresponding support coefficient can be directly called from the database when the axial compression bearing capacity of the longitudinal truss is calculated. SUMMARY

[0003] The application solves the technical problems that the accuracy of the support coefficient c in the existing calculation is insufficient and the finite element calculation efficiency is low, and provides a quick design method of a frame truss riveting structure.

[0004] The technical solution of the application is a quick design method of a frame truss riveting structure, which comprises the following steps:

[0005] (1) a standard multi-span beam finite element model is established, and the support coefficient c is calculated by the finite element method for different combinations of longitudinal trusses and cross frames;

[0006] (2) the support coefficient c values under different frame truss combinations are stored in a database;

[0007] (3) a given frame truss riveting structure in a combination form is provided, and the support coefficient c value corresponding to the given frame truss combination form is called from the database to calculate the axial compression bearing capacity of the riveting structure under the given frame truss combination form;

[0008] (4) for a plurality of possible frame truss combination forms, iterative optimization is performed, that is, the calculation in step (3) is performed, and the optimal frame truss combination form is obtained from the calculation result.

[0009] Preferably, the standard multi-span beam finite element model comprises four identical cross frames and a longitudinal girder, the four cross frames are parallel and symmetrically arranged with the longitudinal girder as the center, from the top end of the longitudinal girder downwards, the span between the top end of the longitudinal girder and the first cross frame is L0, the spans between adjacent cross frames are L1, L2 and L3 in turn, and the span between the bottom end of the longitudinal girder and the bottommost cross frame is L4, and L1=L2=L3>L0=L4 is satisfied.

[0010] Preferably, the support coefficient c is calculated by the following method:

[0011] Finite element modeling is performed on different combinations of longitudinal girders and cross frames, and the axial compression ultimate bearing capacity P of the longitudinal girder is obtained by finite element calculation;

[0012] The support coefficient c under the current combination of longitudinal girders and cross frames is obtained by the formula c=PL 2 / π 2 EI.

[0013] Wherein, L is the length of the unstable span, E is the modulus of the longitudinal girder, and I is the sectional moment of inertia of the longitudinal girder.

[0014] Preferably, for each different sectional type of longitudinal girder applied to the riveted structure of the frame truss in engineering, each different sectional type of cross frame is matched, the support coefficient c is calculated for each longitudinal girder and cross frame and stored in the database, and the database is regularly updated; the c values in the database are sorted and stored according to the combination of the sectional moment of inertia of the longitudinal girder and the cross frame; for the sectional combination falling between two data in the database, the c value is selected by linear interpolation according to the sectional moment of inertia of the longitudinal girder and the cross frame.

[0015] The beneficial effects of the present application compared with the prior art are:

[0016] (1) After years of calculation of multiple frame truss riveted structures, it is found that although the engineering algorithm can quickly give the bearing capacity of the frame truss riveted structure, there is always a deviation from the test results, sometimes a large deviation, which brings risks to the application in engineering, and the main reason for the deviation is that the accuracy of the support coefficient c value calculated by the engineering algorithm is poor, and the present application can improve the calculation accuracy of the support coefficient to improve the calculation accuracy of the frame truss riveted structure;

[0017] (2) When the finite element is used to calculate the frame truss riveted structure, the calculation accuracy and efficiency of the finite element depend on the engineering experience of the calculation personnel due to the need for modeling simplification and reasonable treatment of boundary conditions of the structure, and repeated modeling and boundary simplification are required for each type of frame truss riveted structure, which is low in efficiency in solving engineering problems. The present application can solve the problem of low efficiency of finite element calculation;

[0018] (3) This invention combines the advantages of finite element method and engineering algorithm, and integrates engineering experience into the calculation of support coefficient c, which can realize the rapid and effective iterative design of frame truss riveting structure. Attached Figure Description

[0019] Figure 1 This is a flowchart of the present invention;

[0020] Figure 2 This is a schematic diagram of the multi-span beam finite element model of the present invention. The boundary conditions in the figure are to release two degrees of freedom along the longitudinal girder direction and the torsional direction along the transverse frame, and the remaining degrees of freedom are all constrained by 0 displacement.

[0021] Figure 3 Finite element model and failure contour plot of Z100-B27 for XC212-34 stringers; a) Finite element model; b) Frame stringer failure contour plot;

[0022] Figure 4 To support the storage of coefficient c values ​​in the database: a) different types of frame and truss combinations, b) longitudinal truss data storage, c) transverse frame data storage; Detailed Implementation

[0023] The present invention will be further described below with reference to the embodiments.

[0024] A rapid optimization design method for frame-truss riveted structures is achieved through the following steps:

[0025] (1) Calculate the support coefficient c

[0026] The support coefficient c value was calculated using the finite element method.

[0027] When calculating the axial compression bearing capacity of a frame-truss riveted cabin using engineering algorithms, the support coefficient c is an important parameter. Theoretically, the value of c is determined by the matching relationship between the bending stiffness and torsional stiffness of the intermediate frame and the bending stiffness and torsional stiffness of the stringers. Currently, the value of the support coefficient c in calculations is mostly based on experience. However, by calculating the value of c through finite element analysis, the stiffness matching relationship between the stringers and the intermediate frame can be accurately reflected, and the support effect of all degrees of freedom (including rotational and translational degrees of freedom) can be taken into account, thus accurately obtaining the value of the support coefficient c.

[0028] Establish a standard finite element model for multi-span beams, as shown in the attached figure. Figure 2 As shown, with spans L1 = L2 = L3 > L0 = L4, the support coefficient c is calculated for different combinations of longitudinal girders and transverse frames. The calculation method is as follows:

[0029] The ultimate axial compressive bearing capacity P of the longitudinal girder is obtained from finite element analysis, and the support coefficient can be obtained as c = PL. 2 / π 2EI, wherein L is the unstability cross-section length, E is the modulus of the longitudinal girder, and I is the cross-section moment of inertia of the longitudinal girder. As L1=L2=L3=400mm>L0=L4=200mm, D=75mm, the longitudinal girder is selected as XC212-34 type surface, 7A09 profile, the cross-section moment of inertia parameters of the longitudinal girder strip and the cross frame are shown in the following table, and the finite element model is shown in the following table. Figure 3 The cross-section moment of inertia parameters of the longitudinal girder strip and the cross frame are shown in the following table. Figure 4 The carrying capacity P=85.96kN is obtained through finite element calculation, so the support coefficient c=85960*400 2 / (pi 2 *70000*28130.4)=0.71.

[0030] (2) Establishing a support coefficient c value database

[0031] The support coefficient c values under different frame girder combinations calculated in (1) are stored in the database, as shown in the following table. Figure 4

[0032] The longitudinal girders and the cross frames of the riveted cabin are vertically arranged, and for each different cross-sectional type of the longitudinal girders applied to the frame girder riveted structure in engineering, each different cross-sectional type of the cross frame is matched, the support coefficient c value is calculated and stored in the database, and the database is regularly updated to ensure the timeliness of the database, the c values in the database are sorted and stored according to the size combination of the cross-section moment of inertia of the longitudinal girders and the cross frames, and for the cross-section combination falling between two data, the c value can be selected by linear interpolation according to the size of the cross-section moment of inertia of the longitudinal girders and the cross frames.

[0033] (3) Calculating the carrying capacity of the frame girder riveted structure

[0034] When calculating the carrying capacity of the frame girder riveted structure, the c value in the database is called according to the matching relationship between the girder and the intermediate frame.

[0035] (4) Optimizing the frame girder riveted structure

[0036] The advantages of the finite element calculation accuracy and the high efficiency of the engineering algorithm are utilized to quickly iteratively calculate the carrying performance of the frame girder riveted structure and complete the optimization design.

[0037] Although the present application has been disclosed with the above preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make possible changes and modifications to the technical solutions of the present application by using the disclosed methods and technical contents without departing from the spirit and scope of the present application, therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, which does not depart from the technical solutions of the present application, all belong to the protection scope of the technical solutions of the present application.​

Claims

1. A rapid design method for a frame truss riveted structure, characterized by, The method comprises the following steps: (1) establishing a standard multi-span beam finite element model, and calculating the support coefficient c for different combinations of longitudinal girders and cross frames by using finite element method; (2) storing the support coefficient c values under different frame-truss combinations in a database; (3) given a frame-truss riveted structure with a combination form, calling the corresponding support coefficient c value in the database to calculate the axial compression bearing capacity of the frame-truss riveted structure under the given combination form; (4) for various possible frame-truss combination forms, iterative optimization is performed, that is, the calculation in step (3) is performed, and the optimal frame-truss combination form is obtained from the calculation result; The standard multi-span beam finite element model comprises four identical cross frames and one longitudinal girder, the four cross frames are symmetrically arranged in parallel and with the longitudinal girder as the center, from the top end of the longitudinal girder to the bottom, the span between the top end of the longitudinal girder and the first cross frame is L0, the spans between adjacent cross frames are L1, L2 and L3 in turn, and the span between the bottom cross frame and the bottom end of the longitudinal girder is L4, and L1 = L2 = L3 > L0 = L4 is satisfied; For each different section type of longitudinal girder applied to the frame-truss riveted structure in engineering, each different section type of cross frame is matched, the support coefficient c is calculated for each longitudinal girder and cross frame and stored in the database, and the database is updated regularly; the c values in the database are sorted and stored according to the size combination of the sectional moment of inertia of the longitudinal girder and the cross frame; For the sectional combination form falling between two data in the database, the c value is selected by linear interpolation according to the sectional moment of inertia of the longitudinal girder and the cross frame.

2. The method of claim 1, wherein, The support coefficient c is calculated by the following method: Finite element modeling is performed for different combinations of longitudinal girders and cross frames, and the axial compression ultimate bearing capacity P of the longitudinal girder is calculated by using finite element method; Using the formula c = PL 2 / (π 2 EI), the support coefficient c is obtained for the current combination of longitudinal girders and cross frames; Wherein L is the length of the unstable span, E is the modulus of the longitudinal girder, and I is the sectional moment of inertia of the longitudinal girder.

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