Predictive seismic shear capacity model of rectangular squat RC shear walls in flexural and shear zones

Abstract

This paper describes a comprehensive assessment of the seismic shear capacity of rectangular squat reinforced concrete walls through collection of up-to-date experimental database results. The theoretical shear capacity of wall specimens are first evaluated by axial-moment interaction curve in order to categorise the walls into shear, flexural-shear and flexural failure modes. It is shown that flexural failure is deemed possible for lightly reinforced squat walls of shear span-to-depth ratio around unity, in contrast with the commonly recognised shear failure merely governs by geometric aspect ratio or shear span-to-depth ratio of the wall. Important parameters contributing to shear strength i.e. shear span-to-depth ratio, axial load ratio, mechanical ratio of vertical and horizontal reinforcements and confinement effects are identified. Statistical multi-parameter regression analysis is adopted to formulate two reliable predictive seismic shear capacity empirical models distinctively for flexural zone and shear zone controlled walls. The proposed models predict the normalised shear stress with concrete cylinder strength, which is more robust compared to shear stress or shear force models. The models demonstrate more reasonable predictions compared to past shear capacity models with different functional forms recommended by other researchers and stipulated in design codes. The models were further affirmed through three squat reinforced concrete walls tested under high axial load. The merit of the proposed models lies within the coverage of the database especially for squat walls subjected to high axial load ratio, thus improves the accuracy of prediction. The high axial load characteristic of non-seismically detailed shear wall buildings with transfer structure in Hong Kong can be evaluated by this study in order to be resilient for future consideration of low-to-moderate seismicity action.