Dynamic performance of steel plate-strengthened reinforced concrete slabs in bending

When Reinforced Concrete (RC) elements are subjected to dynamic loading they fail at much lower load than their ultimate static load capacity, due to accumulated induced stresses. Many old structural elements in bending experience degradation due to dynamic loading and/or enhanced loading that they were not originally designed for. In order to prevent demolition or collapse of such RC concrete structures when they are distressed, especially those of historic importance, it may be necessary to improve their load capacity by strengthening with appropriate steel plate strips. This study assesses the performance of externally bonded (EB) steel plate RC concrete slabs, under dynamic loading. A total of 14 RC slabs were cast with ready-mix concrete and cured appropriately. Thereafter, surface preparation of 12 of the RC slabs and steel plates was carried out before the slabs were strengthened by externally gluing different thicknesses of steel plate strips to their surfaces using epoxy adhesive. The composite slabs were subsequently subjected to two-line dynamic loading up to maximum of 4 million cycles at constant frequency and load amplitude. The deformation modes and composite performance of the strengthened slabs were used to assess their fatigue life at the failure load cycles. It was observed that the composite slabs failed at different number of cycles. Based on the observed performance of the steel plate-strengthened slabs, it was concluded that all the steel plate-strengthened RC slabs survived 4 million load cycles at 60%P_u with 2 Hz frequency and 15 kN amplitude. Also, 8 mm steel plate-strengthened RC slabs sustained dynamic load better than those of 4 and 6 mm thick steel plates, at 4 Hz frequency and 30 kN amplitude.