Research Status And Existing Problems Of Pipe Truss Structures

The earliest application of steel pipe structure began in the United Kingdom. Then in the 1980s, people had a deeper understanding of steel pipe structure design, and had some formal publications on steel pipes, such as "CIDECTBook"; after 1985, IIW The fatigue design of the welded steel pipe connection was given and the design method of the static welding connection was updated. The second edition of this design method was published (IIW1989). The new design method has been widely recognized internationally and has been adopted by international organizations, such as European Design Eurocode3, U.S. AWS, and CIDECT design guidelines.

The truss structure design is mainly the design of the external dimensions, component dimensions and node forms. The overall design is mainly the overall layout of the truss, span, height, internode distance, truss spacing and arrangement of the web members. The number of connections should be minimized. Selection of the I-member size is related to the form of the joints, and should be calculated by the joint bearing capacity and the strength of the members. And stability check to determine. Research on pipe truss structure at home and abroad mainly focuses on the analysis of pipe nodes.

Because the destruction of the nodes often leads to the failure of several bars connected to it. As a result, the entire structure is destroyed. There are three main research methods for the static performance of pipe joints: test, analytical theory and numerical analysis (finite element method).

1. Experimental study: At first, people could only understand the load-bearing performance of the pipe node through experiments and verify the design plan. In the 1960s, the static load test and fatigue test of various pipe joints were performed using the seamless steel pipe model. In 1974, a model test of the space tube node was conducted for the first time, and the bearing capacity of four KK-type pipe joints under axial force was tested. In 1990, the KK-type space tube node under axial force was tested. In recent years, the wide application of pipe nodes in civil buildings has made the research of pipe nodes important. Shen Zuyan et al. (1998) conducted model tests on the K-tube joints of n specimens and examined the design of the cantilevered main truss of the Shanghai 80,000 stadium.

2. Classical analytical theory research: Since the pipe joint is a structure welded by several round steel pipes, it is equivalent to a space column shell structure. Therefore, many scholars use elastic cylindrical shell theory to analyze.

Due to the complex boundary conditions and geometrical shapes of the pipe nodes, it is difficult to solve the partial differential equations, and there is a large gap between the analytical solution and the actual engineering on the basis of a large number of simplifying assumptions. However, these studies have deepened the understanding of tube nodes and laid the foundation for future research.

3. Finite element calculation: In recent years, with the continuous acceleration of computer computing speed and the development of programming languages, the finite element method has been used to calculate the ultimate bearing capacity of pipe joints. Liu Jianping used finite element software ANSYS to calculate the ultimate bearing capacity of tubular T, Y, and K joints subjected to axial loads. He Dongzhe used the finite element software ADINA and independently developed front-end processing programs to study the bearing behavior of the TT-type circular pipe joints under axial force, in-plane bending moment, and out-of-plane bending moment, and carried out the formula with the existing formula. Based on this, a semi-empirical formula for the in-plane bending moment bearing capacity of the TT type circular pipe joint is proposed. Fu Zhenyu analyzed the stress distribution of the cross section of the K-gap rectangular pipe branch, the deformation of the joint and the influence of the node parameters on the strength of the joint using the finite element method. Finally, the ultimate bearing capacity formula of the joint was given. The VnoMISeS yield criterion is generally used in finite element analysis and isotropic reinforcement is assumed. In recent years, continuum damage mechanics method was used to simulate the formation and expansion of cracks, and corresponding fracture criteria were established.

A worker from a steel pipe company, which is located in China.