ABSTRACT
Consistent with the displacement based seismic design principles (Priestly et al. 2007), the ultimate drift capacity of a RC shear wall can likely be a key damage indicator under seismic action. In view of the rare research findings done on seismic drift behavior on squat walls (defined by M/VL) especially with high axial load ratio (ALR = P/ Afc′), this paper describes a comprehensive assessment of the ultimate drift capacity of rectangular squat RC walls through collection of up-to-date experimental database results. The squat wall can be categorised into shear (Zone S) or flexural (Zone F) failure modes through simple axial-moment interaction curve. Statistical multi-parameter regression analysis is adopted to formulate two reliable ultimate drift capacity prediction empirical models distinctively for Zone S and Zone F controlled walls. Apart from the maximum shear strength capacity, ALR, shear span to depth ratio, this paper explores the influence of reinforcement details (i.e. mechanical ratio of vertical and horizontal steel reinforcement, confinement effects in
1 INTRODUCTION
1.1 The “squat” phenomenon in shear walls
The lack of statutory seismic design codes in Hong Kong has exposed the risk of earthquake damage on many non-seismically detailed Reinforced Concrete (RC) shear walls with high axial loads induced by gravity. These limited ductile shear walls may suffer from brittle shear coupled with axial failure due to rapid degradation of strength and stiffness during a rare earthquake event. The structural response of the lower part of a shear wall under high axial stress and lateral force is similar to that of a squat wall, measured by wall shear span to wall length ratio (M/VL = a/L). Readers are advised to refer to the general notation section for the definition of parameters and symbols.
