Efficiency of CFRP Strengthening in Controlling the Deflection of RC Beams in a Redundant Structural System

Abstract

One-way reinforced concrete joist floor with wide shallow beams (WSBs) are used widely in building construction throughout the Middle East. Situations arise when it is desirable to strengthen a specific member or a group of members in a floor to reduce their deflections. Extensive work has been made on the strengthening of isolated members using fiber-reinforced polymers (FRP) for providing much needed data on the member performance and characteristics where the ultimate goal is to apply these findings to actual complex existing structures. Judging by studies on individual isolated members strengthened with FRP, a substantial improvement in deflection control is expected. However, this cannot be directly applied to members in redundant structural systems before confirming that experimentally. This paper presents the results of an investigation on the effectiveness of carbon FRP (CFRP) external strengthening for the purpose of reducing deflection of WSBs as part of joist floor of a prototype reinforced concrete building with highly redundant structural system. The results indicated that using CFRP strengthening did not show much improvement in controlling the deflection of the beams. The experimental work was also complemented with theoretical explanation of the expected effectiveness in terms of parallel spring analogy. Further, a nonlinear finite element analysis for the floor system was conducted. The results of that analysis were in good agreement with the experimental findings.