Abstract:
Reinforced concrete coupled wall systems can be designed to perform as an effective seismic load resisting system with high levels of energy dissipation. However, during the 2010/2011 Canterbury earthquakes, several coupled walls were found to have not conformed to the inelastic mechanism intended by current concrete design standards. The current NZS 3101 design philosophy for coupled walls follows the capacity design approached, and strength assessment of structural elements is an essential requirement of this method. Following recommendations made by the Canterbury Earthquakes Royal Commission, the draft amendment 3 to NZS 3101:2006 included provisions to account for the axial restraint of the floor when estimating the over-strength of coupling beams. A finite element model was developed to capture the non-linear cyclic response of coupled walls systems and verified against existing experimental results. The model was used to conduct a parametric study to benchmark the effect of the floor systems on the seismic response of coupled walls typical of that built in New Zealand. The key parameters investigated included the wall, coupling beam, and floor dimensions, as well as reinforcement ratios in the wall piers and coupling beams, and foundation beam designs. The results obtained from this parametric study illustrated the increase in the shear capacity and reduction in the axial elongation of coupling beams due to interaction between the floor system and coupled walls, leading to considerable change in the coupling ratio and inelastic response of the wall system.
