CFRP COMPOSITES FOR STRENGTHENING RC BEAMS WITH LARGE SQUARE OPENING AT SHEAR: FEM & EXPERIMENTAL

Openings are necessary to be provided in a reinforced concrete (RC) beam to allow for the passage of utility ducts and pipes. The utility ducts and pipes are needed to accommodate essential services in a building such as sewerage, power supply and telephone cable. In a pre-planned construction, the location of openings is known thus internal strengthening was performed by providing sufficient steel reinforcement around the opening. However, in a post-planned construction, the location of opening is unknown and it is usually requested by M&E contractors to create an opening in an existing structure or a newly cast beam. The presence of opening in a reinforced concrete beam changes the beam cross-sectional behaviour to a more complex one and causes many problems including reduction in beam capacity and stiffness, increase in cracks and deflection. An investigation was conducted on using carbon fiber reinforced polymer (CFRP) composites to strengthen RC beams with large square opening at critical location at shear. The dimension of the beams was 120x300x2000 mm. The study consists of two solid control beams, three un-strengthened beams with opening at 0.5d, d and 1.5d from the support. Strengthening using CFRP composite was conducted on rc beam with opening at a distance d from the support. The beam simulation was conducted using a non-linear finite element program, ATENA and verified by an experimental program. The result shows that crack pattern of FEM correlated well with the experimental results. Strengthening of reinforced concrete beam with large square opening at distance d from the support could re-gain the beam capacity of the un-strengthened beam, Square d to about 50% in FEM and 5% in experiment. Optimum strengthening can be simulated using ATENA to increase the beam capacity with the most economic usage of CFRP.