Experimental Study On Seismic Performance Of Steel Reinforced Concrete Short-Pier Shear Wall With Built-In Prestressed X Composite Bracing

6 specimens of SRC short-pier shear walls in reduction ratio of 1/2 were designed in this paper. Six specimens have the same form of reinforcement and axial compression ratio and the variables include shear span ratio, ordinary bracing, prestressed bracing and with or without prestressed bracing. Based on the experimental tests under quasi-static cyclic loading, the seismic performance of the SRC short-pier shear walls were investigated. The failure modes of the specimens were observed, the change process of prestressing force was recorded, and the load-displacement curve was measured. Based on these test the carrying capacity, the mechanisms of stiffness degradation and energy dissipation, the characteristics of the hysteretic behavior, ductility performance and prestressing action mechanism of the specimens were revealed. In the meanwhile a comparative analysis based on the calculation results of three capacity calculation methods with the experimental results were carried out. Main conclusions can be drawn as follows:(1) 6 specimens have experienced four similar stages, including elastic stage, crack stage, yield stage and failure stage. Shearing-compression failure occurred in specimens PSW-2～SW-6 whose shear span ratio are smaller while bending-shearing failure happened in specimen PSW-1 whose shear span ratio is bigger.(2) The crack number, width and extension length of the specimens with prestressing force can be reduced. The cracking form has been changed, making the angle of inclination flatter than those without prestressing force. At the same time,the cracking load of specimens with prestressing force has been improved, especially for specimen PSW-2 which has built-in prestressed composite bracing, its cracking load increased by 39.3% than those without prestressing force.Ordinary specimens without prestressing force had little effects on their cracking load.(3) The yield load and load carrying capacity of the specimens with ordinary bracing and prestressed bracing can be improved to a large extent, especially for specimen PSW-2 which has built-in prestressed composite bracing, its yield load and peak load are increased by 12.1% and 11.9% respectively than specimen SW-3 which has built-in prestressed finishing threaded steel bracing, increased by 27.2% and 26.5% respectively than the reference specimen SW-6.(4)The stiffness of the specimens with built-in prestressing force can be increased, and the stiffness degradation has been effectively suppressed in the later loading test after the peak load, thus ensure a better load carrying capacity and deformation ability.(5)Prestressing loss has been decreased among specimens with built-in prestressed composite bracing and their prestressing force has been fully used. On the contrary, specimens with built-in prestressed finishing threaded steel bracing bear a larger loss of prestressing force.(6) Specimen SW-5 with prestressed finishing threaded steel ordinary bracing and specimens with prestressed bracing have a better seismic energy dissipation performance and ductility. The energy dissipation performance and ductility of specimen SW-5 was the best due to its good bonding performance between finishing threaded steel and concrete.(7) Under the effect of prestressed composite bracing,specimen PSW-2 has the highest cracking load, yield load and peak load among the six specimens, and in the process of loading, its prestressing loss was the smallest. However, as the bond-slip failure occurred between steel and concrete of the composite bracing and edge component, its strength and stiffness degenerated rapidly after the peak load, the load-displacement curve was also slightly in the shape of "pinch approach" and the energy dissipation and ductility were worse than specimen SW5.Therefore, the energy dissipation performance and ductility of the prestressed composite bracing can be further enhanced after solving the problem of bonding performance between steel and concrete.(8) In the process of loading, the distribution of strain of the longitudinal bar and steel of the specimens with or without prestressed bracing was essential in line,which conformed to the rule with "plane section assumption".(9) Bearing capacity calculation model based on "plane section assumption" and softened strut-and-tie model are suitable for specimens with prestressed bracing due to the small deviation between the calculated values and measured values of the bearing capacity.