Study On Seismic Behavior Of Monolithic Precast Concrete Shear Wall Structure With Low Axial Compression Ratio

The monolithic precast concrete shear wall structure is a building system suitable for housing industrialization in China. Our group proposed a new type of construction method which is formed by rebar overlapping connection in the pre-reserved area between two precast portions for the monolithic precast concrete shear wall structure. An 11-storey monolithic precast concrete shear wall pilot project with this type of construction is intended to be built.In order to study the seismic behavior of this new type of structure, both quasi-static tests and Finite Element Method (FEM) analysis of full-scale specimens were conducted, Push-over analysis and performance-based seismic design analysis of the whole structure of the precast pilot project were also completed and discussed. The main research work and achievements are as follows:1. Quasi-static tests of 7 groups including 21 pieces of full-scale specimens were conducted to study the seismic behavior of the precast structure. Some of the precast specimens are with both horizontal and vertical joints formed by the pre-reserved area and edge members, respectively; the other of them are with vertical joints formed by the cast-in-situ concrete in the middle of the specimen. The main variable parameters are axial compression ratio and ratio of shear span to effective depth.The similarities and differences of the performance such as crack patterns and failure modes between the precast specimens and their cast-in-situ counterparts are analyzed. The seismic behavior of the precast specimens, such as hysteretic behavior, skeleton curves, stiffness degradation, inter-story drift ratio, energy dissipation capacity and ductility are studied and compared to their cast-in-situ counterparts.2. The tested bearing capacity of the precast specimens and the FEM results of them are found being 5.7% and 8.4% less than that of their cast-in-situ counterparts, respectively. By use the relevant formulas given in the Chinese "Technical specification for concrete structures of tall building", the formulas for calculating the shear strength of the monolithic precast concrete shear wall members subjected to eccentric compressive loading are proposed, and the related reduction factor is also proposed.3. The performance-based seismic design analysis for the 11-storey precast monolithic shear wall structure is conducted. The recommendation is given, when a performance-based seismic design is performed, the interface between concretes cast at different times should be considered as a connecting part or connecting key part and its check requirements should be the same as that of the adjacent member or adjacent key member, respectively. The analytical result shows that the rebars across the horizontal joints of the reinforced part at bottom of the 11-storey precast monolithic shear wall structure should be increased, in order to meet the capacity requirements for structrual performance level 4 under fortification earthquake actions.4. On the basis of a comprehensive analysis of the mechanisms of shear transfer between concretes cast at different times, a contact algorithm with a combination of surface-based cohesive behavior and friction model is proposed to simulate the interface between concretes successfully. Based on the ABAQUS finite element analysis software, the elasto-plastic analysis of the precast specimens and their cast-in-situ counterparts are carried out; the Push-over analysis of the structure of the precast pilot project and its cast-in-situ counterpart are also conducted; all of the interfaces in both precast members and structure between concretes are considered.Both the top floor displacement and the maximum inter-story drift ratio of the precast structure under rare earthquake are slightly bigger than that of its cast-in-situ counterpart. Both of them can meet the current design codes.5. For monolithic precast concrete shear wall with rebar overlapped in pre-reserved area, recommendations on improving the seismic behavior of the precast shear wall structure and specimens are also given.