Effect of FRP Wrapping Stiffness and Concrete Cover on Lap Splice Failure Behavior

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Title: Effect of FRP Wrapping Stiffness and Concrete Cover on Lap Splice Failure Behavior

Author(s): Rayed Alyousef, Timothy Topper, and Adil Al-Mayah

Publication: Special Publication

Volume: 322

Issue:

Appears on pages(s): 1.1-1.20

Keywords: bond behavior, thickness of concrete cover, GFRP and CFRP strengthening and lap splice.

Date: 6/18/2018

Abstract:

Lap splices are an easy to implement low cost method of transferring force between reinforcing bars in concrete structures. However, the bond between lap spliced bars is usually the weakest region in a reinforced concrete structure. Fiber reinforced polymer materials (FRP) are widely used to strengthen and repair lap splices because of their high strength, durability and ease of handling. Researchers have found that increased concrete cover provides an increase in bond strength similar to that supplied by wrapping with FRP sheets. Currently the FRP industry produces a new generation of high stiffness FRP sheets that provide a high degree of confinement and large increases in bond strength to lap splices.

This paper compares the effectiveness of wrapping with very high stiffness carbon FRP sheets (CFRP 900), wrapping with low stiffness glass FRP sheets (GFRP 430) and no wrapping on the bond strength of lap splice connections for various concrete covers. The test variables were the amount of concrete cover and the wrapping condition. The results showed that the GFRP wrapped beams had an increased in bond strength of approximately 25% compared to the unwrapped beams for each of the concrete covers. However, the CFRP wrapped beams had a percentage increase in bond strength that decreased as the concrete cover increased. The CFRP wrapped beams had increases in bond strength of 71%, 60% and 44% compared to the unwrapped beams for concrete covers of 20mm, 30mm and 50 mm, respectively.