The use of plain bars in R/C structures is prohibited in newly developed structural codes. Anyhow, many R/C buildings which plain bars were used as their reinforcement are currently existed in Iran. Iranian government approved a special lumped budget to improve the vulnerability of existing buildings. For that reason a guideline was published for assessment of seismic strength of buildings based on performance based engineering concepts. In order to accurately evaluate the performance of a structure during earthquake a nonlinear earthquake response approach is usually performed. There is a lack in literature to find a proper member hystersis model for nonlinear earthquake response analysis of R/C buildings with plain bars. The objective of this research is to study hystersis behavior of R/C members with plain bars. Two identical R/C structural members one with plain bars and another with deformed bars were designed and constructed in almost same conditions. The members were subjected to cyclic load to obtain and compare their hystersis diagrams. It was observed that pinching behavior was increased in hystersis diagram of R/C member with plain bars, which result in reducing of energy dissipation. Moreover, the use plain bars in R/C members resulted in loss of strength in these structures. Cracks were much concentrated at member ends with plain bars which can lead to shortening of plastic hinge length. Hystersis model of R/C structural members with plain bars can be obtained by applying proper strength reduction factors and pinching factors to conventional models of R/C members with deformed bars.
展开▼
