An Experimental Investigation on the Effect and Mechanism of Side Cover Spalling for Slender Beams Subjected to Shear
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Date
2021-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Reinforced concrete members should have an adequate safety margin against shear failure, which
happens to be brittle and sudden. A lot of variables contribute to the shear resistance of beams, and
to predict the resistance their influence to the shear behavior should be studied thoroughly. Past
researches indicated that side cover spalling was observed for beams subjected to shear, signifying
out of plane deformation had resulted from an in-plane loading. This observation however has not
been explored enough to understand the mechanism and effect of side cover spalling in the overall
structural resistance of reinforced concrete beams.
To investigate the effect and mechanism of side cover spalling under different variables seven full
scale shear critical reinforced concrete beams were tested under one-point monotonic loading.
Variables under consideration were concrete side cover thickness, stirrup cage width, and stirrup
spacing. The specimens were also analyzed in a two-dimensional nonlinear finite element
software, VecTor 2. Furthermore, the study assessed current code provisions and shear design
theories for the design of beams subjected to shear, and checked whether or not spalling affects
the ultimate resistance of a beam.
From the experimental program out of plane deformation strains were recorded for all tested
specimens regardless of their side cover thickness. This deformation led to side cover spalling near
peak load exemplifying that, stirrups are planes of weaknesses where spalling happens. Variable
side cover thickness and stirrup spacing had observable effect on the spalling mechanism of the
beams. The variation of side concrete cover thickness and spalling did not compromise the load
resistance of beams as long as the core concrete confined within the stirrups was adequate enough
to resist the applied loads. However, pre-peak spalling followed by premature failure happened for
specimens designed with a relatively reduced stirrup cage width.
Existing international codes including Eurocode 2 (EN 1992-1-1:2004), ACI Standard (ACI 31814),
Canadian
Standard
(CSA
A23.3-14),
and
Japanese
Code
(JSCE
Standard,
1986),
consider
the
entire
beam
width (bw) to be effective for shear resistance and consequently uses it as such for
ultimate capacity prediction. Code prediction gave an overestimated failure load for specimens
with reduced stirrup cage width, which demonstrates the inadequacy of design code provisions for
beams subjected to shear with regards to the usage of the entire beam width ( bw) for capacity
prediction.
Description
Keywords
Side Cover Spalling, Slender Beams, Shear