Research On Seismic Performance Of New Assembled Joints And Precast Stiffening Braced Frame Structure

Compared with the traditional cast-in-situ construction, precast building technique, which is considered as sustainable development techniqu, has many exclusive advantages, such as reduced construction period, reduced the consumption of energy during the building whole life. However, integrity and seismic performance are crucially determined by the connection reliability, thus having a better understanding of the connection performance under low reversed cyclic loading is of great significance to promote the development of precast structures.This paper firstly introduces the experimental study on the precast CFST column to RC beam with steel girder connections, based on which calculation method for moment- rotation relationship curve of this kind of connections is proposed, and then a series of nonlinear finite element analysis has been conducted to study the mechanical performance of this kind of connections, and connection design proposal formula is given. The main research content is as follows:① Full scale cyclic experimental study on 6 new precast CFST column to RC beam and a braced frame with steel girder connections have been conducted, and full scale cyclic experimental on 12 new precast CFST column to RC beam with sleeves connections and a frame have been conducted to compare the seismic performance with the precast CFST column to RC beam with steel girder connections. Their failure pattern and mechanical characteristics have been observed, their bearing capacity, load-displacement hysteresis curves, skeleton curves, strength degradation and stiffness degradation, ductility and energy dissipation capacity, rotation of plastic hinge area, mechanical properties such as plastic corner have been analyzed. The seismic performance of the two kinds of connections is compared. Experimental results have shown that the two types of connections have plump load- displacement hysteresis curves, unobvious strength and stiffness degradation, high ductility and excellent seismic performance, precast CFST column to RC beam with steel girder connections have a better seismic performance than precast CFST column to RC beam with sleeves connections. This kind of new type of precast connections has good ductility and energy dissipation capacity, meeting the requirements of current seismic design code.② By using FEA software ABAQUS, numerical study on six new precast CFST column to RC beam with steel girder connections have been conducted, which are in good agreement with the test values, thus the validity in the selection of element types, material constitutive and damage criterion of rationality are verified. On this basis, the influence on the seismic performance of connections due to the length of the girder, the distance from the sleeve to the column, reinforcement ratio, axial pressure ratio, the strength of the concrete and steel have been studied. Initial stiffness and moment-rotation curves obtained by parameter analysis are given. Bending moment-rotation practical calculation formula are deduced by using three parameters power model; Bending moment-rotation practical calculation formula are in good agreement with test values and measured values and can evaluate the parameters’ influence on the connections, thus setting stone for the design of this two kind of connections.③ The load carrying capacity of the new precast CFST column to RC beam connections has been studied. Shear force performance of new precast CFST column to RC beam with steel girder connections are studied. Weakening effect of the shearing resistance due to hoop tensile stress under vertical axial force and cyclic loads at beam end has been studied; The constitutive model of the steel used in the core section of the connections are shear line model, concrete horizontal section shear model are adopted to the inner and outer layer of the concrete. A new calculation formula of the shear bearing capacity of the connection has been deduced, and the calculated results are in good agreements with the measured values, thus the validity of the calculation formula has been verified.