Seismic performance of precast shear walls prestressed via post-tensioned high strength bars placed inside grouted corrugated pipes

摘要

The seismic performance of precast concrete shear walls depends on the mechanical behavior of the connections to the foundation and especially on the energy-dissipation capacity that is strongly related to connection deformability. With the focus on wall-to-foundation connections, the seismic performance of four verticallyelongated shear walls (height-to-width ratio close to two) is investigated by testing as many full-scale specimens, either cast-in-place (one ?reference? specimen) or precast (three specimens). The three precast specimens are equipped with front and back metallic corrugated pipes into which three types of reinforcements are placed in concrete close to the vertical sides, i.e., ordinary bars (PW1), high-strength bars (PW2) and post-tensioned bars (PW3), whereas ordinary spliced bars are placed in the central part of the precast specimens. The cast-in-place specimen (CW) is vertically reinforced only with ordinary continuous bars. After bar placement, the pipes are filled with grout. In this way, the connection between the bars protruding from the footing and the bars reinforcing the shear wall is very effective face to seismic action. Coupling post-tensioned bars with ordinary spliced bars improves the stiffness of the shear walls. The specimens are tested under low-cycle loading, to investigate the lateral resistance, the energy dissipation capacity and ductility, to monitor crack evolution and to study hysteretic behaviour. The local deformation of the concrete at the wall-footing interface (into which epoxycoated concrete keys are incorporated) is also examined. The test results show that (a) the four shear walls have a similar bearing capacity (PW2 and PW3 have slightly stronger bearing capacities than CW and PW1); (b) the shear walls PW2 and PW3 exhibit similar ductility to the shear wall CW under cyclic loading; and (c) the shear wall PW1 is the least ductile of the investigated specimens.