Experimental Load-Drift Relations of Concrete Beam Reinforced and Confined With High-Strength Steel Bars Under Reversed Cyclic Loading

Abstract

High-strength steel bars have different characteristics from normal-strength steel bars. Thus, the use of high-strength steel bars still needs to be investigated further before it can be used confidently in concrete structures. In the design, a reinforced concrete beam should also have enough ductility besides its loading capacity. One of the indicators identifies that a structure has sufficient ductility is its ability to maintain the load steadily due to progressive deformation. This paper presents the test results of three reinforced concrete beams designed with concrete strength (fc) of 30 MPa. Two different yield strengths (fy) of longitudinal and transverse reinforcements were used, namely, 420 and 550 MPa. The cross-sectional dimensions of the beams were 200  300 mm with a total span of 2000 mm and a rigid stub at the midspan. The beams were simply supported by double rollers at their tops and bottoms. These special supports were located at both ends of the beams. The load applied at the midspan of the beam through the rigid stub with the displacement control. The loading pattern protocol by the drift was set from 0 to 5.5 percent. Based on the test results, it can be seen that the beams with high-strength steel bars could achieve a higher load capacity than the beams with normal-strength steel bars. On the other hand, the beams with high-strength steel bars produced lower deflection than the beams with normal-strength steel bars. Furthermore, it can be concluded that all the beams could withstand the minimum required of 3.5 percent. None of the beams indicated brittle failures. All of the beams could survived until the end of the cycles at a drift of 5.5 percent. This condition indicates that the reinforced concrete beams with higher-strength reinforcement (fy of 550 MPa) could also maintain their load capacities under large deformation beyond the first yielding of the longitudinal steel bars.

Proposed Formulation for Predicting Deflections of CFRP-Rc Beams

“…A complete structural replacement has several disadvantages, such as high material and labor costs, increased environmental impact, and inconvenience due to structural malfunctions, such as traffic problems. Therefore, several previous studies have suggested opting for structural repair and enhancement using reinforcement whenever it is feasible [4,5].…”

Effects of High-Strength Steel Bars on Short Concrete Columns Under Axial Load

“…The yield stresses above 500 MPa have shown a shorter or no clearly defined yield plateau in the stress-strain diagram. A study was conducted to determine the effects of the yield strength of steel bars on their elongations [28][29][30][31]. The results showed that the elongations of the steel bars with a yield strength of 420 MPa were longer than those of the steel bars with a yield strength of 550 MPa.…”