The Research On The Seismic Behavior Of R.C Space Joints Strengthened By Basalt Fiber Reinforced Plastic

Reinforced concrete frame structure is used in industrial and civil construction commonly. As the key of the connection of the beam and column and the weak part of the structure, the mechanical properties of reinforced concrete beam-column joint is complex in the earthquakes. Because of the damage of the earthquake, poor-quality construction and the change of function, some current buildings cannot meet the code of design. In order to improve the seismic performance of frame, it is necessary to do some researches about repairing and retrofitting the frame joints.FRP has attracted wide attention in the strengthening technology which has advantages in mechanical behavior, convenient construction and space saving. As one of the FRP, the basalt fiber with low price and high intensity which is a hot topic in research and development. In this paper, basalt fiber is used to strengthen the beam-column joints and the finite element analysis is used to examine the behavior of the strengthened and non-strengthened joints under low frequency reversed load to study the seismic performance of beam-column joints strengthened by basalt fiber. The following is this paper’s main work:(1) After designing 4 apace middle beam-column-slab-lateral nodes with different forms numbered SJ1~SJ4, general programs ANSYS and ABAQUS are used to model the nodes. The result of the calculation of the mode which compared with the test data provides reasonable reference for verification of numerical analysis and the applicability and characteristics of two programs can be compared.(2) Based on the results, the seismic performance of beam-column joints by reinforced with different materials and different ways are compared to analysis the development of concrete cracking, damage mode and carrying capacity.(3) Analysis of mechanism of beam-column joints to conclude the contributors of the reinforcement. Formulae are brought forward as the reference of design base on the existing reinforced concrete nodes.Compared the results of finite element analysis with the theory of the mechanism of beam-column joints, the conclusions of this paper are summarized as follows:(1)By analyzing two kinds of the finite element software, the simulation results accord with experiment simulation. But it is difficult to simulate the model under low frequency reversed load by ANSYS. However, ABAQUS can complete full cycle load because of its excellent capacity of processing nonlinear problem. It is found that there are differences between the definitions of the concrete unit and description of the concrete crack, so the appropriate program can be selected depends on the needs.(2) It is found that the seismic performance, carrying capacity and damage mode of strengthened nodes are improved by comparing the output of numerical simulation. It demonstrates the effectiveness of basalt fiber reinforcement concrete beam-column joints.The seismic strengthening effect is insignificant by using of carbon fiber and basalt fiber, the reinforce way of non-continuous U basalt fiber and continuous U basalt fiber to strength the joints. The shear strength improvement by using carbon fiber and continuous U basalt fiber is more obviously. Therefore, the way to reinforce the concrete beam-column joints by basalt fiber can be optimized after guaranteeing the effective anchorage.(3) The study of the basalt fiber reinforced beam-column nodes found that the contributions of the improvement of the seismic performance mainly are the following three aspects: First, the fabric on the n surface of the node can provides the shear resistance capacity in the core area which is similar to stirrups; the second is the basalt fabric can inhibit the expansion of concrete effectively under the load and reducing the principal tensile stress of the stirrup that produced by the superposition of stress suffered by the expansion of concrete; the third is fabric which extended to the beam, column and slab around node improve the mechanical properties of the components and enhance the components constraint capacity of the node, so the shear ability of the node is enhanced. According to the results of finite element analysis, a formula of shear is proposed and strength coefficient of basalt fiber is determined.