Abstract
This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength and ductility of concrete are improved by appropriate arrangement of the stirrup confinement. Firstly, the concrete damage evolution can be relatively restrained with the increase of the stirrup volume ratio. Secondly, higher stirrup yield strength usually causes larger confining pressures and slower concrete damage evolution. In contrast, higher concrete strength leads to higher brittleness, which accelerates the concrete damage evolution. A plastic strain expression is obtained through curve fitting, and a damage evolution equation for circular stirrup-confined concrete is proposed by introducing a confinement factor (C) based on the experimental data. The comparison results demonstrate that the proposed damage evolution model can accurately describe the experimental results.
Highlights
The allocation of reinforcement stirrups is an important measure to improve the mechanical properties of compression members or other structural components under compression because stirrups allocated perpendicularly to the axial compression/maximum principal stress orientation are able to confine the transverse deformation of the core concrete
The ascending curvescurves of stirrup-confined concrete specimens show a linear portion portion followed by a plateau and the descending curves were considerably broader with greater followed by a plateau and the descending curves were considerably broader with greater ductility
Strength and ductility of reinforced concrete can be improved by stirrup confinement effect
Summary
The allocation of reinforcement stirrups is an important measure to improve the mechanical properties of compression members or other structural components under compression because stirrups allocated perpendicularly to the axial compression/maximum principal stress orientation are able to confine the transverse deformation of the core concrete. By using different approaches (Richart et al, 1928 [2]; Kent and Park, 1971 [3]; Sheikh and Uzumeri, 1980 [4]; Mander et al, 1988 [5]; Karabinis and Kiousis, 1994 [6]; Spoelstra and Monti, 1999 [7]; Montoya et al, 2004 [8]; Papanikolaou and Kappos, 2007 [9]; Rousakis et al, 2008 [10]; Karabinis et al, 2008 [11]; Monti and Nisticò, 2008 [12]; Moghaddam et al., 2010 [13]; Jiang and Wu, 2012 [14]; Peter et al, 2013 [15]; Nisticò and Monti, 2013 [16]; Nisticò et al., 2014 [17]; Gambarelli et al, 2014 [18]; Nisticò, 2014 [19]; Wei and Wu, 2014 [20]) These studies confirmed that confinement (steel and/or FRP) improved the strength of reinforced concrete members. Improving the concrete strength, stirrups can lead to the increase of the Materials 2016, 9, 278; doi:10.3390/ma9040278 www.mdpi.com/journal/materials
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