Strengthening of Reinforced Concrete Stepped Beam Using Cotton Belt (New Technique)

Abstract

Abstract The stepped beam is a type of non-prismatic beams that extend the stepped joint by stress collection and require adequate detail for this joint to prevent early failure. This research demonstrates an experimental study aimed at the behaviour of reinforced concrete stepped beams. The status issue is the premature failure of the stepped joint. The experimental program consists of eight concrete beams. All beams are tested under a four-point load. Three variables are studied in this work, the first of which is compressive strength, which is normal strength of 40 MPa and high strength of 80 MPa. The second variable is the details of the steel reinforcement at the stepped joint and the third variable is the strengthening with a cotton belt. Models achieved increases ranging from (26.3-37.4) kN, (1.88-3.95) mm, and (31.75-116.882) kN.mm in the ultimate capacity, deflection, and energy absorption respectively. Whereas it showed a decrease ranging (14.38-27.68) in the initial stiffness for the compression strength variable. As for the rebar detail variable, it showed an increase ranging between (39-138) kN, (7.5-28.29) mm, (244-3099.619) kN.mm, and (22.285-31.425) kN/mm, for the maximum load, deflection, energy absorption, and initial stiffness, respectively. On the other hand, the strengthened beams achieved an increase in the maximum load by 120% with a slight decrease in stiffness by 3.5% concerning an unstrengthened beam.