Damage evaluation of lightly reinforced concrete walls in moment resisting frames under seismic loading

An experiment was conducted on four lightly reinforced concrete (RC) wall specimens to study the effects of axial force, amount of shear reinforcement, and shear span to wall length ratio on their seismic behaviors such as load and displacement capacities, damage progress, and failure modes. The prototype specimens represented lightly RC walls, which suffered severe damage during the 2011 off the Pacific coast of Tohoku Earthquake. Shear type damage was observed for three specimens tested under double curvature. Increasing the amount of horizontal reinforcement and providing 180-degree hook anchorage reduced the development of shear cracking. A quantitative seismic damage evaluation in terms of crack width, crack length, and concrete spalling area was carried out to investigate the correlation between seismic damage and lateral drift. The damage level of walls was assessed using the 2004 Architectural Institute of Japan (AIJ) Guidelines, which takes into account the level of damage such as residual crack width or stress level of concrete and reinforcement. Considering the total amount of damage (crack length and spalling area), the criteria of the guidelines well captured damage level of lightly RC walls. In order to simulate the damage process as well as hysteresis curves of the tested specimens, finite element (FE) analysis was conducted. The analysis simulated the wall capacities with high accuracy and its crack distributions agreed well with the experiment for all specimens. Additional FE analysis with 210 case studies validated the design equations for flexure and shear capacities.