Title: Behavior of compact L-shaped spandrel beams with alternative web reinforcement
Date Published: March - April 2019
Volume: 64
Issue: 2
Page Numbers: 39 - 54
Authors: Vivek Hariharan, Gregory Lucier, Sami Rizkalla, Paul Zia, Gary Klein, and Harry Gleich
https://doi.org/10.15554/pcij64.2-04
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Abstract
Open web reinforcement has been shown to be an effective
alternative to closed stirrups in the webs of slender
precast concrete L-shaped spandrel beams subjected
to combined shear and torsion.1–6 For slender beams,
an open reinforcement scheme is a better alternative
to the traditional closed stirrups mandated by the
American Concrete Institute’s (ACI’s) Building Code
Requirements for Structural Concrete (ACI 318-14) and
Commentary (ACI 318R-14)7 because the beams are
easier to produce with open reinforcement. Although
the behavior of slender L-shaped beams (having aspect
ratios of 4.5 or greater) with open web reinforcement
has been well documented, the use of alternatives to
closed stirrup reinforcement for compact L-shaped
cross sections having aspect ratios much less than 4.5
has not been investigated previously.
This paper presents an experimental study in which four
full-scale, 46 ft (14 m) long, precast concrete, compact
L-shaped beams were tested to failure. One of the test
specimens served as a control and was designed with
traditional closed stirrups. The remaining three beams
were designed with alternative open and segmented
reinforcement configurations.
The results of the study demonstrate the viability of
replacing closed stirrups with alternative open and segmented
web reinforcement in compact L-shaped spandrel beams. All four beams behaved satisfactorily at
all loading stages and failed at loads much greater than
the factored design loads. When failure occurred in the
end region of the compact L-shaped beams with open
reinforcement, no spiral cracking or face-shell spalling
were observed, which is contrary to the failure mode
associated with the torsion design concept of ACI 318-
14.7 Rather, the observed failure planes in the compact
L-shaped beams were similar to those observed in
slender L-shaped beams, with skewed bending along a
diagonal crack extending upward from the support. The
results confirm the potential to simplify the design and
detailing of compact L-shaped beams by using alternative
transverse reinforcement details proportioned with
a design approach based on failure in combined shear
and torsion.