Performance of Partially Damaged Squat Shear Walls under Reversed Cyclic Loading

Abstract

Reinforced concrete (RC) shear walls can resist lateral loads effectively in a high rise structural system. Squat shear walls are encountered in nuclear power plant structures to resisting earthquake forces. This paper reports on some experimental investigations on behaviour of RC squat shear walls partially damaged under quasi-static loading (monotonic and reversed cyclic). Six large scale RC squat shear walls with boundary elements were tested to failure. Important variable of this study include height of wall maintaining all other parameters constant. Three sets of shear walls, containing two in each set, with aspect ratios 1.5, 1.25 and 1.0. In each set one wall was tested under monotonic lateral load, whereas the second walls with displacement reversals under lateral push and pull. These walls were tested under quasi-static loading up to failure. The tested shear walls with partial cracking were repaired and again subjected to above loading. The repair methodology involves removal of damaged concrete, straightening of steel bars (no rupture of reinforcement) and filling of cracks with cement grout. Testing of repaired shear walls was terminated after significant strength loss and deterioration in subsequent cycles. Load vs. displacement hysteresis loops, mode of failure, and crack pattern and overall response of the shear walls have been described. The seismic performance of all the shear walls has been analysed in terms of shear strength, stiffness degradation and ductility. Shear walls showed significant increase in ultimate lateral load at small aspect ratio. At small aspect ratios, shear walls exhibited brittle shear failure with horizontal cracking in the web.