Dynamic performance enhancement of RC slabs by steel fibers vs. externally bonded GFRP sheets under impact loading

Recently, to improve the dynamic behavior of Reinforced Concrete (RC) slabs under impact load, the methods of externally bonding Glass Fiber Reinforced Polymer (GFRP) sheets to slab and internally reinforcing concrete by steel fibers have been proposed. Nevertheless, it is required to investigate the comparison between these two methods on response of RC slabs under impact loads. In this study, the influence of volume fraction of steel fibers, the number of GFRP sheet layers (one or two) and the arrangement of GFRP sheets (covering the whole or parts of surface), are examined. Performance of fourteen 1000 x 1000 x 75 mm concrete slabs including one plain slab, one steel RC slab, three steel RC slabs containing steel fibers with different volume fractions and nine steel RC slabs strengthened with externally bonded GFRP sheets or strips under impact loads induced by drop weight is experimentally examined. In this article, crack development, failure modes and dynamic responses including displacement-time, strain-time, as well as acceleration-time are investigated and compared between slabs with various configuration. In addition, finite element analyses are carried out using LS-DYNA explicit software. The results indicate that increasing the bottom layer GFRP enhances the performance of RC slabs under impact loads. In general, slabs with totally bottom GFRP layers provide better performance than those with steel fibers.