Deflection Control of Concrete Wide Beams Supporting Columns Using CFRP Composites and Honeycomb Plates.

Abstract

In the Middle East, RC joist slab systems with wide beams are widely used for residential floors. However, when these beams support planted columns, excessive deflection beyond code limits is often observed, despite adequate flexural and shear design. This paper experimentally assesses, for the first time, the efficacy of using carbon-fiber-reinforced polymer (CFRP) sheets alone versus a novel hybrid system comprising CFRP sheets and CFRP/honeycomb plates in controlling deflection in RC wide beams with planted columns. Four RC wide beam specimens at half-scale, each featuring a planted column, were tested to failure. Two control specimens, the first one was designed to reflect standard construction practices. It was sufficiently designed in flexure and shear, but its deflection exceeded code requirements. The second was designed to satisfy the code deflection requirements. The remaining specimens were strengthened using two different techniques: one with externally bonded CFRP sheets and the other with the hybrid system. The findings demonstrated a marked improvement in the flexural performance of the retrofitted wide beams, with peak load increases of 65-71%, stiffness gains of 63-67%, and reduced deflections meeting serviceability requirements (deflection at peak load was reduced by 45-48%). Furthermore, an analysis procedure was developed to estimate the flexural strength and deflection of these beams.