Experimental campaign of reinforced concrete walls with non-seismic detailing

Abstract

About 2% of reinforced concrete (RC) buildings taller than nine stories suffered important damage during 2010, Mw=8.8 Chile earthquake. Extensive localized damage likely occurred as a result of high axial loads, poor concrete confinement and inadequate bar buckling restraint. Most walls were designed without boundary confinement because NCh433, the Chilean seismic design code at that time, was based on ACI318-95 and it eliminated the transversal reinforcement requirements at walls boundaries. Aimed to understand the observed localized damage in RC walls with non-seismic detailing, an experimental campaign is proposed. To design the wall specimens, a representative prototype wall was defined based on wall characteristics of five damaged buildings. The test program of nine ½-scale specimens is presented and some preliminary test results are summarized. The wall specimens were subjected to constant vertical load and to cyclic horizontal displacement with increasing amplitude. The test matrix include walls with axial load ratios of 0.15, 0.25 and 0.35, wall thickness of 100 mm and 75 mm, aspect ratio (M/Vl_w) of 2.5 and 1.9, and walls with different vertical and horizontal reinforcement detailing. The flexural-compressive failure mode exhibited by damaged walls during the earthquake was reproduced in the tests. The wall specimens evidenced bar buckling of vertical bars, brittle concrete crushing, and out-of-plane buckling, which suggest that the axial load and the thickness of RC walls should be limited in critical walls to prevent brittle localized failures.