Seismic behavior of reinforced concrete slender walls subjected to variable axial loads

Abstract

Reinforced concrete (RC) shear walls are the major lateral load-carrying structural components in high-rise buildings. Under strong earthquake motions, the axial loads of RC walls are not constant axial compression, but may be in tension, resulting in the axial load of RC walls varying from compression to tension. In this study, three RC slender wall specimens (shear-to-span ratio λ = 2.0) were tested to study the effect of the fluctuating range and loading patterns of variable axial forces on their cyclic behavior, including failure modes, hysteretic response, strength and deformation capacity. Test results indicated that the final failure of RC slender walls subjected to variable axial forces was controlled by flexural failure in the compressive-flexural direction. The hysteretic curves of RC slender walls were asymmetric and substantively different from the hysteretic curves of RC slender walls with constant axial loads. The fluctuating range of axial forces had a limited influence on the shape of hysteretic curves, while the loading patterns significantly changed the shape of these hysteretic curves. Under the variable axial forces, the lateral strength and deformation capacity of RC slender walls depended on the fluctuating range of axial forces, while loading patterns had limited influence when the fluctuating range of axial forces kept constant. The loading patterns had a limited influence on the lateral stiffness of RC slender walls, while the increase of fluctuating range of axial forces increased the difference between compressive-flexural and tensile-flexural lateral stiffness. No matter in tensile-flexural or compressive-flexural directions, the assumption that the wall section remains plane after deformation is suitable for RC slender walls under the variable axial forces, and enables reasonable estimations of yielding and peak strength. Finally, a finite element model was developed for predicting the cyclic behavior of RC walls under the variable axial loads.