Numerical modelling of reinforced concrete walls with minimum vertical reinforcement

Recent experimental results have shown that current minimum vertical reinforcement limits in many concrete design standards are insufficient to ensure that large ductility can be achieved during earthquakes. A detailed finite element model was developed in VecTor2 to provide a tool for further investigating the seismic behaviour of lightly reinforced concrete (RC) walls. The model was verified using experimental data from recent RC wall tests with minimum vertical reinforcement, and was shown to accurately capture both the overall response and local response parameters with good accuracy such as the cyclic hysteresis response, crack pattern, and vertical reinforcement strains. The model could also be used to estimate the drifts at which reinforcement buckling initiated and when reinforcement fractured occurred. The results from additional analyses showed that a potential size effect exists when considering the failure of lightly reinforced concrete walls. When keeping the reinforcement ratio and shear span ratio constant, the lateral drift capacity decreased significantly as the wall length increased. Using reinforcement with higher strength and lower ductility did not significantly impact the crack pattern, but did decrease the lateral drift capacity of the walls. Furthermore, reducing the strain hardening ratio of the reinforcement, or increasing the concrete strength, both resulted in a reduction in secondary cracking in the plastic hinge region and a reduced lateral drift capacity. It is recommended that wall length and average material properties should be accounted for when assessing the seismic behaviour of lightly reinforced concrete walls or when developing design standard requirements.