In-plane lateral behaviour of PVC modular concrete form squat walls : experimental and numerical study

The in-plane lateral performance of modular concrete form squat walls comprising prefabricated Polyvinyl Chloride (PVC) permanent forms and reinforced concrete cores was experimentally and numerically undertaken. The PVC encasement make additional confinement to the reinforced concrete core that makes the formwork attractive, however, the interaction between the encasement and the concrete make an irregular internal concrete core and therefore further studies are required. Eleven wall specimens of different aspect ratios ranging from 0.5 to 2.0 were subjected to incrementally increasing monotonic drifts to failure after imposing eccentric vertical loads as indicative of gravity loading conditions. Two samples were further selected and investigated by adopting push-out tests to measure in-plane shear capacity of PVC form walls. The experimental measures including concrete crack propagation and crushing, loads and displacements pertinent to capping and failure stage, and ductility capacity were discussed. After stripping the form off, a failure mode in walls demonstrated discontinuity in the concrete crack propagation due to penetration of the form web into the concrete core which did not act as a solid concrete wall. Finite element simulations were undertaken according to suggested modelling techniques and the credibility of the numerical method was investigated through comparison with experiment results. Implications of change in design parameters including axial load ratio, wall aspect ratio, concrete strength, vertical, horizontal reinforcement ratio, and cyclic loading regime were further examined through a detailed parametric study. It demonstrated that the peak lateral load capacity and post-peak negative stiffness of PVC form squat concrete walls were highly influenced by axial load ratio. The influence of concrete strength on peak lateral response of the walls was in direct proportion to the axial load ratio. Increasing horizontal reinforcement ratios showed the modest influence on the peak lateral load capacity of the walls.