Case study on the restoration of flexural capacity of continuous one-way RC slabs with cutouts

Introducing openings in existing reinforced concrete (RC) slabs can severely weaken the slabs because of the cut out of the concrete and reinforcing steel. This paper reports field tests on the use of carbon fiber-reinforced polymer (CFRP) composite strengthening techniques to restore the flexural capacity of RC slabs after having openings cut out in the positive moment region. The uniqueness of this study is that the tests were performed on an existing multistory RC building that was scheduled for demolition. Five tests on five different slabs were conducted using three different strengthening techniques—namely, externally bonded (EB) CFRP plates, EB CFRP plates with CFRP anchors, and near-surface mounted (NSM) CFRP strips—to determine the most effective system for strengthening. Test results showed that the three strengthening techniques increased the load-carrying capacity of the slabs with openings, with the NSM technique being more effective than the EB technique. However, the use of CFRP anchors to mechanically anchor the EB plates prevented complete detachment, and hence enabled the restoration of the slab to its full flexural capacity.