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.
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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.
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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.
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