Comparison of Minimum Vertical Reinforcement Requirements for Reinforced Concrete Walls

摘要

Recent research and post-earthquake observations have raised doubts over the crack distribution and deformation capacity of reinforced concrete (RC) walls with vertical reinforcement contents close to minimum requirements. To investigate the seismic behavior of lightly reinforced concrete walls, the minimum vertical reinforcement requirements for ductile RC walls from concrete design standards worldwide were examined. A series of numerical analyses were conducted to compare the cracking behavior of flexural walls using a finite element model that was developed and validated using existing test data. The results from the analyses showed that RC walls designed in accordance with requirements for minimum distributed vertical reinforcement did not generate many cracks within the plastic hinge region. Lumping additional reinforcement at the ends of the wall, as required by some design standards, generally improved the distribution of cracking and ductility. However, concentrating too much reinforcement at the ends of the wall resulted in the web region being vulnerable to the development of large, widely spaced cracks that may contribute to poor seismic performance. Therefore, it is recommended that the ratio between reinforcement concentrated at the end of the walls and distributed reinforcement through the web region be controlled. Furthermore, concrete and reinforcing steel strengths were shown to significantly influence the crack pattern and deformation capacity of the RC walls with minimum vertical reinforcement and should be accounted for when developing design standard requirements.