Optimum Strengthening of R/C Beams with Large Opening at Shear using CFRP Laminates

Openings are provided in a reinforced concrete beam to allow for the passage of utility ducts and pipes. The openings are usually provided at the most suitable location in a beam that best accommodate the pipes and ducts to pass through. Critical design and adequate treatment is required if the opening is to be provided at critical part of the beam. This can be done by providing sufficient reinforcement around the opening during the design stage. However, problem often arise when opening is to be created after the construction or in the existing structure, especially at critical shear location in a reinforced concrete beam. In this research, an optimum strengthening of reinforced concrete beam containing a large square opening at shear were conducted using carbon fiber reinforced polymer (CFRP) laminates. A total of five beams were tested to failure under four point loading. The dimension of the beams was 120x300x2000 mm. The square opening was placed at a distance d away from the support. The experimental study was validated by a nonlinear finite element program, ATENA. The crack pattern, beam behaviour and load deflection curves obtained from experimental study were discussed. A good agreement was achieved between the results of experimental study and numerical modelling. Results show that the optimum strengthening configuration with CFRP laminates could re-gain 20% of the original beam capacity. Numerical modelling can be useful to determine the optimum strengthening configuration which could re-gain and restore the beam original capacity with the most effective usage of CFRP laminates.