Abstract
Structures are expected to have ductile behavior under major earthquakes. One requirement to achieve this ductile behavior is when the structures have no shear failures in their elements. This paper discusses a new method by using the embedded steel truss in the flexural plastic hinges of beam to avoid shear failure. As already known that the shear strength provided by the concrete will be decreased when the ductility of flexural plastic hinges develop in a member. Therefore, a conservative procedure by ignoring the role of concrete in flexural plastic hinges in resisting the shear demand is adopted by some codes. This will increase the demand for shear reinforcement provided by the stirrup or transverse reinforcement in the plastic hinge; yet it still does not ensure that the shear failure does not come to happen. From the laboratory test results under cyclic loading in this study, it can be noted that the beam with embedded steel truss in the plastic hinge has better hysteretic behavior than the one without the embedded steel truss. The evaluation of test result is also shown the strength of the beam with the embedded steel truss in the plastic hinge is not reduced with an increase in the amplitude of the drift of 1.4 to 3.5. Besides, the strength of the beam without embedded steel truss in the plastic hinge is reduced with an increase in the amplitude of the drift after reaching 2.5.
Highlights
The embeddedment of steel truss in reinforced concrete is adopted to preserve the shear strength provided by the concrete for raising the energy dissipation capacity and the ductility of conventional reinforced concrete elements
In order to compute the structural parameters of the reinforced concrete cantilever beams with and without embedded steel truss in the flexural plastic hinge, the specimens were subjected to cyclic loads that simulate seismic action, the hysteresis response curves drawn in Figure 10 and 11 from the tests were used to assess the ultimate strength and the ductility of the system
Before the final drift for BK-150 specimen at drift of 2.75%, as seen in Figure 16a compared to the other one in Figure 16b, the specimen without steel truss (BK-150) gets wider and it has deeper diagonal cracks than the specimen with embeded steel truss has in the flexural plastic hinge (BU-150). These results reveal that the embedment of steel truss in the flexural plastic hinge area of the beam can increase the shear capacity within this zone
Summary
The performance of a critical region will be controlled by detailing and amount of the reinforcement. The flexural ductility increases because of the shear strength degradation in plastic hinge regions, the initial cracks should occur in the reinforced concrete beam section and it should spread immediately and than it results in the beam shear failure. A conservative procedure by ignoring the role of concrete in flexural plastic hinges in resisting the shear demand is adopted by some codes. This will increase the demand for shear reinforcement provided by the stirrup or transverse reinforcement in the plastic hinge; yet, it still does not ensure that shear failure does not come to happen. An experimental investigation on two cantilever beams with and without steel truss was coducted to analyze the shear behavior of the proposed beams in terms of modes of failure, strength, stiffness,
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