Displacement Ductility of Helically Confined HSC Beams

Abstract

This paper presents an experimental investigation of the effect of helix pitch and helix diameter on beam behaviour through testing 10 helically confined beams. Two groups of beams had exactly the same geometry and reinforcement; with the only differences being the helices diameter and pitch. 8 mm helix was used in the first group of beams and 12 mm bars in the second group. The helix pitches varied between 25 mm and 160 mm. Beams' cross section was 200 300 mm, with a length of 4 m subjected to four point loading. The main results indicate that the helical effectiveness is neglected when the helical pitch is 160 mm (helix diameter) and the displacement ductility index increases as the helical pitch decreases. Finally, there is a considerable release of strain energy responsible for spalling off the cover.

Effect of Concrete Compressive Strength and Compression Reinforcement in Compression Zone on the Ductility of Reinforced Concrete Beams

“…The failure mechanism of the entire tested beams was yielding of tension steel bar and developing crack numbers and height followed by crushing the concrete in the top of compression zone. The extension of the crushing zone of group A was greater than that of the control beam B 1 and in increase with ρ ′ while the crushing zone of group B was smaller than that of the control beam and in decrease with f c ′ and that is clear in Figure (3).…”

“…Chloride free liquid admixture commercially named TopBond 603 complies with ASTM C 469-86 [12] was used. Properties and description of the used superplasticizar are shown in Table (3).…”

“…uctility is a desirable structural property because it allows stress redistribution and provides warning of impending failure; therefore, it is a structural design requirement in most design codes. In reinforced concrete (RC) structures, ductility is defined as the ratio of post yield deformation to yield deformation which it usually comes from steel [1][2][3][4].…”

“…This mode of failure is ductile and is guaranteed by designing the tensile reinforcement ratio to be substantially below (ACI 318 requires at least 25% below) the balanced ratio, which is the ratio at which steel yielding and concrete crushing occur simultaneously. The reinforcement ratio thus provides a metric for ductility, and the ductility corresponding to the maximum allowable steel reinforcement ratio provides a measure of the minimum acceptable ductility [2,3].…”

Flexural Reinforcement of Over-Reinforced Beam by Ultrahigh Performance Concrete Layer

“…At present, many researches restrict the compression zone of beams in the form of spiral rebar or stirrups. Hadi and Elbasha [17] made experiments on 10 beams constrained by spiral rebar to study the ductility of beams with spiral rebar applied in the compression zone. Te results showed that the defection ductility coefcient of beams constrained by spiral rebar was larger, and the defection ductility coefcient increased as the pitch decreased.…”