Behavior Study of SIFCON-Reinforced Concrete Composite Brackets under Repeated Load

Abstract

This study investigates the performance and ductility of concrete brackets made of normal concrete and fiber-reinforced concrete (SIFCON) composites. SIFCON was used to strengthen the brackets under monotonic and repeated loads. Eleven bracket specimens, including homogeneous and hybrid reinforced specimens, were tested. Two of them are control specimens tested under static load to determine the ultimate load for defining the repeated loads. The other nine specimens are classified into three groups based on the SIFCON reinforcement shape, with each group containing three steel fiber percentages (6%, 4%, 2%).Where in group A the SIFCON used for the entire volume of the bracket, in group B the SIFCON used in rectangle shape in tension zone of the bracket, and in group C the SIFCON used in trapezoidal shape.

The study focused on determining the maximum load capacity, load-deflection relationship, toughness, strain, first crack load, and failure mode of each specimen at the final stage. It is observed that using SIFCON had a significant effect on the structural response of concrete brackets. The strengthening increased the ultimate load capacity of the best tested model for group A under repeated load up to 3.2 times the control model's capacity after 21 loading cycles. In the group B&C the maximum load up to (2 and 1.8) times the control model's capacity after (17 and 13) loading cycles. There is also a substantial increase in absorbed energy and toughness of concrete brackets when using this type of reinforcement, up to 31 times for group A and (19 and 9 ) times for group B and C respectively . Additionally, a reduction in the width of concrete cracks was observed. The use of SIFCON resulted in an increase in the amount of endurance for repeated loads and an increase in the amount of strain. This is due to its higher strain capacity compared to normal concrete and its greater flexibility.