Effect of plastic zone levels on the responses of concrete shear walls subjected to earthquakes

Generally, in reinforced concrete (RC) core wall buildings, the formation of one plastic hinge at the base is preferred; this is called the single plastic hinge (SPH) approach. During a severe earthquake, this approach results in significant moment demand in the upper regions of the wall due to the effect of higher modes of vibration. This study considered RC core walls of 30-, 40- and 50-storey buildings, designed using a response spectrum analysis. The SPH, dual plastic hinge (DPH), triple plastic hinge (TPH) and extended plastic hinge (EPH) approaches were examined using fibre element models and non-linear time history analysis. The DPH and TPH approaches respectively contain one and two plastic hinges at the upper levels of the wall in addition to the base plastic hinge. The effect of the locations of the upper plastic hinges on the seismic response of the core wall was investigated. The results showed that there is not a distinct level for the upper plastic hinge location to minimise the envelope of different demand quantities simultaneously. The curvature demand of the middle plastic hinge in the TPH case was higher than the base curvature demands. Reducing the resistant moment at the wall base by reducing the reinforcement ratio can help to balance curvature demands along the height of the TPH model.