Testing of reinforced concrete walls in pre-1970s multi-storey buildings

Abstract

Reinforced concrete (RC) walls in older (pre-1970s) multi-storey buildings were not designed with ductile detailing and capacity design principles in New Zealand. During the 2010/2011 Canterbury Earthquake series, several older RC walls suffered significant damage. Failure modes included fracture of longitudinal reinforcement, brittle crushing and shear failure. The undesirable seismic behaviour of these walls highlighted the need to assess the existing RC walls and refine the current seismic assessment guidelines. The structural characteristics and vulnerabilities of these pre-1970s RC walls in New Zealand have been reviewed. It was found that most of these older walls feature potentially non-ductile detailing, including a thin section (< 200 mm thick) with a single layer of distributed reinforcement, light reinforcement ratio (0.17%- 0.33%), and lack of confined boundary elements at the ends of the wall. To investigate the seismic performance of typical pre-1970s walls, a total of four singly reinforced walls with reinforcement ratio of 0.25% and shear span ratio of 2 were tested. The observed lateral-load response, hysteretic behaviour, drift capacity and failure modes are discussed. The experimental results confirmed the potential failure modes and limited deformation capacity of older RC walls with non-ductile detailing that had been observed following recent earthquakes.