Seismic behavior and modeling of T‐shaped reinforced concrete walls under high axial force ratios

Abstract

AbstractThis paper presents large‐scale quasi‐static tests conducted to investigate the seismic behavior of slender T‐shaped walls under a high axial compression force ratio of approximately 0.19. Four specimens were designed per various codes and design methods for comparison. All specimens failed in a flexural mode, characterized by the crushing of concrete and buckling or fracture of boundary longitudinal rebars at the web toe. The specimens designed per the US code ACI 318‐19 provisions and designed using displacement‐based method exhibited satisfactory deformation capacity with an ultimate drift exceeding 2.0%, which validates the effectiveness of the provisions and displacement‐based method for T‐shaped walls under high axial force ratios. However, the specimen designed per the Chinese code GB 50011‐2010 experienced a sudden drop in strength after 1.0% drift in flange‐in‐tension loading, indicating insufficient design of the special boundary element at the web toe and the necessity of improvement of the current Chinese code provisions. The flexural strength of the T‐shaped wall specimens can be accurately estimated using cross‐sectional analysis. Analysis of the test data indicated that the effective stiffness of the T‐shaped RC walls with an axial force ratio of no greater than 0.1 was significantly lower than 0.35EcIg, while that of the T‐shaped walls with an axial force ratio of 0.19 reached 0.5–0.7EcIg. Existing equations did not provide accurate estimate of the effective stiffness of T‐shaped walls. The lateral drift limit formulation developed by Segura and Wallace could reasonably estimate the lateral drift capacities for the T‐shaped RC wall specimens under high axial force ratios. Finally, three conceptually different models, namely the MVLEM‐3D, SFI‐MVLEM‐3D, and multi‐layer shear element models were adopted for the simulation of T‐shaped RC walls. All three models reasonably predicted the flexural strength capacity (mostly less than 15% error) and the effective stiffness (13%–43% error) of the T‐shaped walls.