Nonlinear Finite Element Study On New Precast Stiffening Braced Frame Structure

Promoting green construction and building materials actively, developing precast and steel structure, improving construction quality and engineering standards are the new requirements of the national government for the construction industry. It is expected that the precast structures accounting for 30% of new buildings constructed in 10 years. Promoting the precast buildings has become not only the applicable, economic, green and beautiful architectural approach, but also the effective way to realize industrialisation production. Traditional cast-in-site structures have many problems such as material waste, environmental pollution, quality problems and excessive labor costs. By contrast, precast buildings have excellent economic benefits and construction efficiency and quality, but they have little influence on environment and environmental protection. However, the traditional precast structure has defects in integrity and seismic performance because of the poor connection between the components, therefore, enhacing the connection between components become greatly critical. In this paper, a series of nonlinear finite element analysis have been conducted on the new rigid joints with steel end connector, stiffening braced frame and composite beams. The main concents of this thesis include:(1) The related parameters for ABAQUS numerical joints model were put forward, such as the unit selection, mesh optimization, contact relationship, boundary conditions, and software settings. This paper established two different FEA joint models by different methods to analyze the advantages and disadvantages of these two modeling methods. Numerical analysis on six joints with steel end connectors was conducted, whose results are in good agreement with the test values, such as the load-displacement hysteretic curves, skeleton curves, ductility, energy dissipation Stiffness and strength degeneration. According to the parameters such as the axial compression ratio, floor slab and reinforcement in beam, the different seismic behavior in cracks, failure modes, stress distribution in steel end connectors of joints was verified.(2) Using the finite element software ABAQUS, considering the mechanical difference between the edge connections and intermediate connections, this paper established six different types of beam-column connections of 12 numerical models. Numerical analysis on the mechanical property of these connections have shown that there was no obvious mechanical difference between the edge connections and intermediate connections. But the intermediate connections have lower load carrying capacity and failed earlier when compared to the edge connections. The joints with steel end connectors behaved better and had better ductility and seismic performance than the other five connections.(3) On the basis of verified six composite beam numerical models, the 125 beam models have been built to do parametric analysis. The values of the length, height and the multiple linear regression equation of the width of the steel end connectors were proposed.(4) By using FEA software ABAQUS, numerical analysis on the mechanical property of a stiffening braced frame and a frame with sleeves connections was conducted, whose results are in good agreement with the test values. Nonlinear finite element analysis results have shown that the stiffening braced frame had a good load carrying capacity and seismic performance, but the strength and stiffness degradation are fast, the ductility and deformation capacity are lower. On the basis of finite element analysis, some suggestion for improving the connector plates of the brace connection were proposed.