Performance of NSM GFRP Retrofitted Postfire RC Slabs Under Monotonic and Cyclic Loadings

This study investigated the performance and mechanical properties of NSM GFRP retrofitted postfire RC slabs under monotonic and cyclic loadings. Experiments were conducted for eight RC slabs exposed to different fires. These postfire slabs were retrofitted with NSM GFRP bars, which were then monotonically and cyclically loaded until failure. The results indicated that the control slab failed in flexure, with steel yielding and a main mid-span crack. NSM GFRP retrofitted postfire slabs failed by either crushing of compressive concrete or rupture of GFRP bars. The tested slabs were characterized by bi-linear behavior. NSM GFRP retrofitting improved the yield and ultimate loads of postfire slabs by ۴۷.۲% and ۱۱۶.۴% on average, respectively. Fire duration was confirmed to be a main factor that significantly reduced the elastic stiffness of NSM GFRP retrofitted postfire slabs by ۶۰.۹% for ۶۰ min of fire. The average plastic-to-elastic stiffness of NSM GFRP retrofitted postfire slabs was ۰.۱۳۲, which was ۳۲ times that of the control slab. The cyclic loading effect caused substantial stiffness degradation of NSM GFRP retrofitted postfire slabs. The average stiffness degradations were ۱۰.۶% and ۷.۲% for original and NSM GFRP retrofitted postfire slabs, respectively. However, the cyclic loading effect caused negligible strength degradation. The combination of increasing fire duration and the cyclic loading effect significantly decreased ductility. Theoretical analyses were carried out to estimate the yield moments of slabs. The analytical equation demonstrated its accuracy in estimating the yield moment capacity of postfire RC slabs without and with NSM GFRP retrofitting. Doi: ۱۰.۲۸۹۹۱/CEJ-۲۰۲۴-۰۱۰-۰۶-۰۱۷ Full Text: PDF

Keywords:

Fire , Reinforced Concrete , Slab , NSM , GFRP , Retrofitting.