Rebar misplacement and construction errors are never intended, but are a fact in today’s fast paced Construction Industry. The additional time and costs associated with retrofits have significant impacts to the projects and their completion.
The Delta Structural Technology team assembled the help from Ravi Kantikar PE, Ankiet Borwanker PE, the Simpson Strong -Tie team, and Anna Polk PE along the research and testing done by Ms. Polk that made this project a success. Shear bolts are a new type of reinforcement developed for punching shear strengthening and retrofit of existing slab-column connections. The shear bolt consists of a headed vertical rod threaded at the other end for anchoring using a washer and nut system. The bolts holes were drilled through the slab, layers of Carbon Fiber were added from strengthening, a layer of glass fiber was installed as an insulator and the bolts were installed in holes drilled in a slab in concentric perimeters around the column.
Advantages of CFRP Shear Bolt Retrofit Systems:
- The shear-bolt retrofit system performed as required to strengthen the slab and increase ductility.
- Installation was faster and less intrusive the removing the entire slab and columns; which allowed for adjacent construction to occur.
- The shear bolts provided the required increase in strength, sufficient to change the failure mode from punching to flexure.
- Shear bolts effectively prevented propagation of shear cracking in strengthened slabs.
- The ACI code punching shear strength predictions for specimens reinforced with shear bolts and CFRP are very conservative.
