Shear-flexure interaction in RAC columns under simulated seismic actions

Inelastic flexural deformations adversely affect shear resistance of columns, and may cause building damage/collapse during earthquakes. In this paper, shear-flexure interaction on seismic performance of reinforced concrete columns constructed with recycled aggregate concrete is experimentally investigated. For this aim, reinforced concrete columns with low shear-span-to-depth ratio (2.3) were designed and constructed so that they reach their flexural lateral load capacities in accordance with capacity design principles, and the effect of shear deformations can be observed only after yielding of longitudinal reinforcing bars due to cyclic degradation. The shear-flexure interaction is characterized based on the amount of transverse reinforcement, and formulated within the framework of conventional reinforced concrete design theory during the design of the columns. These columns are then tested under the combined effects of axial and reversed cyclic lateral loads to simulate seismic loading. The recycled concrete aggregate is sourced from waste of low strength concrete, and replaced with 50% of natural coarse aggregate for the concrete mix. Comparison with columns constructed of natural aggregate is also presented in the study. The test results showed that the reinforced concrete columns either made of natural aggregate concrete or recycled aggregate concrete exhibited similar seismic performances for different interactions of shear and flexure. As the ratio of transverse reinforcement is reduced the deformation capability was reduced due to more pronounced effect of shear deformations. In addition, the load-displacement relationships determined through theoretical analysis were found to be compatible with the experimental data. Furthermore, a discussion on the minimum transverse reinforcement provisions of EN 1998-1, ACI 318-19 and TBEC-18 is also presented in order to investigate whether it is possible to reduce the required ratio of minimum transverse reinforcement per technical documents for the columns located in low to moderate seismicity regions.

Automated summary

This paper experimentally investigated the shear-flexure interaction on seismic performance of reinforced concrete columns constructed with recycled aggregate concrete, finding that shear deformations have a detrimental effect on seismic performance of columns. However, columns made of natural or recycled aggregate concrete exhibited similar seismic performances under different interactions of shear and flexure, with reduced deformation capability observed when the ratio of transverse reinforcement is decreased. The study also discussed the possibility of reducing the required ratio of minimum transverse reinforcement per technical documents for columns located in low to moderate seismicity regions.