Reinforced Concrete Infilled Shear Walls for Aseismic Strengthening

Abstract

Five half-size reinforced concrete frames were constructed and tested to determine experimentally the effectiveness of infilled walls in strengthening existing framed structures against earthquake loads. The one-story, one-bay frames which measured 66 in. by 108 in. were tested under static, reversed cycle loads. One specimen was the unstrengthened open frame; the second used a wall cast monolithically with the frame; the third used a wall cast-in-place after the frame was constructed; the fourth used a single precast panel fitted within the frame and mechanically connected to top and bottom beams; and the fifth used a wall made of six small precast panels which were mechanically connected within the frame and then joined together. Response of the open frame and the frame with monolithically cast wall provided reference limits for the remaining specimens. The cast-in-place wall behaved like the monolithic wall until the wall-frame connection failed just below the beam. The precast infilled walls behaved in a combined frame and shear wall action. The maximu~ strength of the multiple precast wall was about half of that of the other walls, although it maintained its load capability over larger deflection levels. Energy dissipation capacities of the two precast and one cast-in-place structures were similar - about half the capacity of the monolithic wall structure. Three general conclusions were: (1) that cast-in-place walls can provide the same maximum strength as an equivalent, new monolithic wall but with less ductility, (2) that multiple precast panels can provide a strong, ductile and easy-to-construct strengthening technique, and (3) that the cyclically degraded load capacity of shear walls should be used in structural design rather than the virgin, monotonic capacity.