MINIMUM AMOUNT OF REINFORCEMENT IN HIGH-STRENGTH CONCRETE T-SECTIONS

Abstract

The objective of this study was to investigate the minimum amount of reinforcement in high-strength concrete T-section and compare it to that of normal­ strength concrete. The minimum amount of reinforcement in reinforced concrete structures is necessary to provide a ductile response, ensure adequate warning of an impending failure at over loads and prevent excessive crack widths at service load. Several national and international standard codes provide empirical formulas for the determination of the minimum amount of reinforcement for normal-strength concrete that sometimes are very different. In some codes, the minimum amount is established on the basis of the ratio between the computed stresses in concrete and steel, some other codes take into account only the steel-yield strength, other codes take the steel-yield strength and the compressive strength of the concrete and some give a minimum percentage of steel that is fixed independently of any geometrical and mechanical feature. The term high-strength concrete is generally used for concrete with compressive strength higher than 6000 psi (421 kg/cm2 . With the great utilization ofhigh-strength concrete, questions have been raised about the applicability of existing design expressions for use in high-strength concrete members. Among those design expressions is the minimum amount of reinforcement in concrete structures and especially for T cross-section. Eleven T-section beams were tested in this study to determine the minimum amount of reinforcement in high and normal-strength concrete T-section. The beams were divided into two groups. The first group of beams consisted of seven high-strength concrete beams. One of them was plain concrete beam, three beams reinforced with high-grade steel and three beams reinforced with mild-grade st el. The second group of beams consisted of four normal-strength concrete beams. One was plain concrete beam and three beams reinforced with high-grade steel.