Strengthening Of R.C. Strap Beams

In this research, tests were carried out on eleven reinforced concrete strap beams to study the effects of some parameters on the flexural strengthening systems and behavior of two groups of reinforced concrete strap beams (I and II) in strap (cantilever) footing strengthened in the negative moment region for flexural by different composite systems. Group (I) strap beams were designed to fail in flexure, While group (II) strap beams were designed to fail in shear (due to lack of proper shear reinforcement). One strap beam in each group was not strengthened and was tested as a base strap beam. One different strap beam with sufficient or required main internal reinforcement was not strengthened and was tested as a target strap beam. The major parameters included in this research were as follows:1. The different strengthening materials (using external bonding of carbon FRP composite sheets and external bonding of thin steel plates).2. The strengthening configurations (involving techniques such as placement of transverse anchorages along the longitudinal composite sheets and wrapping the carbon FRP sheets around the vertical sides of strap beams).3. The internal transverse reinforcement ratio (transverse reinforcement are closed stirrups with ratios 0.67% for group (I) and 0.12% for group (II)).The responses of the beams in terms of ultimate load, vertical displacement, strains, and modes of failure were examined.