Efficient strengthening of opened-joint for reinforced concrete broken slabs

Reinforced concrete broken slab presents a crucial element that exists in all multi-story buildings. Normally, it can be used as the flight of the stair. In many cases such element is in urgent need for strengthening or upgrading due to change of the usage or any construction errors. The current paper presents three different strengthening strategies for opened-joint broken slabs in the aim of doubling their flexural resistance. The adopted strategies were the application of Externally Bonded Carbon Fiber Reinforced Polymer (EB-CFRP) sheets, adding thin layer of Ultra High-Performance Strain-Hardening Cementitious Composites (UHP-SHCC), and the application of hybrid system integrated both former techniques. The studied parameters were the anchorage system of the CFRP sheets at the opened-joint as well as the connection between the substrate slab and the UHP-SHCC layer. Based on the overall structural performance and exhibited ductility, the application of properly anchored EB-CFRP sheets on a well-connected UHP-SHCC layer enabled the substrate broken slab to exhibit the most favorable behavior. Finally, a new stitching procedure was proposed in order to construct a precast slab similar to a monolithic one and then strengthened using the same strengthening strategies. Its performance showed comparable results against the results of the monolithic broken slab.