Strengthen strategies for reinforced concrete haunched beams using fibre reinforced polymer fabric and engineered cementitious composites

Abstract

External strengthening of reinforced concrete haunched beams with and without shear reinforcement has been investigated by using carbon and basalt fiber reinforced polymer fabrics. In addition, the flexural behavior of reinforced haunched beams which are partially and entirely produced from engineered cementitious composite has been tested. The samples, which were produced from self-compacting concrete, engineered cementitious composite, and a combination of them, were prepared and tested via four-point loading tests. Reinforced haunched beams were divided into two strengthening groups. Group 1 included the shear strengthening of self-compacting concrete reinforced haunched beams (beams without stirrups) by the consideration of various strengthening configurations with both fiber-reinforced polymer fabric types. Group 2 included the flexural strengthening of reinforced haunched beams via fiber-reinforced polymer fabrics and/or engineered cementitious composite. The obtained results were depended on the ultimate load capacities, load-displacement curves, crack patterns, and failure modes of strengthened reinforced concrete haunched beams. Experimental results show that the strengthening material and strengthening configuration influence the mechanical behavior of reinforced concrete haunched beams considerably. However, the effect of strengthening configuration was higher. The highest increase in load capacity was 72.8% for shear strengthening (group 1), while the highest increase was 28.8% for the flexural strengthening group (group 2). Furthermore, the U-shaped anchorage with fiber-reinforced polymer fabrics prevented the premature failure of engineered cementitious composite layer and fiber-reinforced polymer fabrics covering the bottom face of reinforced haunched beams and increased the load capacity of reinforced haunched beams, while some losses were observed in ductility. The replacement of the concrete with engineered cementitious composite on the tension side increased the load capacity of reinforced concrete haunched beams.