Lightly reinforced and precast concrete walls: Recent research and design recommendations

Abstract

The Canterbury Earthquake Royal Commission made a number of recommendations that led to research related to the seismic behaviour and design of lightly reinforced and precast concrete walls. The key objectives of this research project include verification of minimum vertical reinforcement requirements for new reinforced concrete (RC) walls, development of assessment guidelines for existing lightly reinforced walls, and development of appropriate detailing for precast concrete panel connections. Large-scale wall tests highlighted that RC walls designed according to current vertical reinforcement limits in NZS 3101:2006 were susceptible to a concentration of inelastic deformation at a small number of flexural cracks. Additional tests confirmed that a small amount of additional vertical reinforcement at the ends of the walls could significantly improve the crack distribution and ductility. These experimental tests and additional numerical models were used to verify the changes to the minimum vertical reinforcement requirements for RC walls proposed in NZS 3101:2006 (Amendment 3). A separate series of wall tests has investigated the seismic behaviour of precast panel connections. The results of tests with grouted metal duct connections confirmed that walls with existing detailing performed adequately when carrying low axial loads, but performance was found to reduce as the axial load and wall length increased. The use of transverse confinement reinforcement around the grouted metal ducts was observed to prevent a brittle connection response and improved the robustness of the reinforcement splice when subjected to large lateral drifts.