Analytical Modeling of Medium-Rise Reinforced Concrete Shear Walls by ProQuest

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									 ACI STRUCTURAL JOURNAL                                                                                TECHNICAL PAPER
Title no. 107-S39

Analytical Modeling of Medium-Rise Reinforced Concrete
Shear Walls
by Hua Jiang and Yahya C. Kurama

This paper describes the analytical modeling of medium-rise              and simplifies the modeling of RC under cyclic lateral loads,
monolithic cast-in-place reinforced concrete (RC) shear walls            including: 1) nonlinear axial-transverse-shear strain interaction;
where nonlinear shear deformations play a significant role in the        2) hysteretic behavior of longitudinal and transverse
wall response under lateral loads. The analytical models use a           reinforcement, including the yielding of the steel; 3)
fiber element developed based on a microplane approach to
                                                                         hysteretic behavior of concrete, including confinement
account for combined axial, flexural, and shear effects in the
nonlinear range. Low-rise shear-critical walls that fail in shear-       effects; and 4) axial-shear crushing of concrete. The two
dominated failure modes are not within the scope of the paper. The       most important advantages of the microplane formulation, as
verification of the analytical models is achieved based on comparisons   compared with other nonlinear shear models (described in
of estimated global (for example, load versus deflection) and local      the following) are: 1) the interaction between axial, transverse,
(for example, reinforcement steel strains and limit states) behaviors    and shear strain fields is included at the concrete and steel
with experimental measurements of RC wall specimens under                material levels, allowing for the modeling of local effects
reversed-cyclic lateral loading.                                         and limit states under reversed-cyclic loading; and 2) the
                                                                         model uses basic uniaxial stress-strain relationships for steel
Keywords: fiber; monolithic; seismic; shear wall.                        and concrete, without the need for other user-specified
                                                                         parameters (for example, no need for a user-defined
                        INTRODUCTION                                     phenomenological shear force versus distortion law).
   Reinforced concrete (RC) structural walls are one of the
most common lateral load systems for buildings in seismic                               RESEARCH SIGNIFICANCE
regions. A large proportion of the walls constructed in the                 Medium-rise RC walls designed according to modern
U.S. can be classified as medium-rise (with wall height-to-              building design recommendations are provided with an
length aspect ratios typically between 2 and 4; refer to                 adequate amount of properly detailed transverse steel
Paulay and Priestley [1992]), where both nonlinear flexural              reinforcement. Shear failure is not expected to occur in these
and nonlinear shear deformations significantly contribute to             walls; however, nonlinear shear deformations can still
the lateral response. This paper describes the analytical                significantly contribute to the lateral response. The behavior
modeling of these walls using a fiber element that accounts              of medium-rise walls under lateral loading is not easy to
for coupled axial-flexural-shear effects in the nonlinear                model analytically; thus, the development of reliable,
range. The model can also be used to analyze “high-rise” RC              reasonably accurate, and relatively simple analytical models
shear walls (dominated primarily by flexural effects with                to capture their fundamental characteristics is an important,
little nonlinear behavior in shear); however, low-rise walls             nontrivial research topic. Axial-flexural models with no
with a primarily shear-dominated response and shear-dominated            nonlinear shear effects can give an inaccurate estimation of
failure are not within its scope.                                        the structural response, and previous models with nonlinear
   Modeling nonlinear shear effects in RC structures is difficult        shear effects are scarce. In accordance with the need for
and previous research in this area is relatively scarce as               research in this area, this paper develops and evaluates a wall
described in the section that follows. Using the microplane              model that can include nonlinear axial-flexural-shear interactions
concept from Bažant et al. (1996), Petrangeli et al. (1999)              at the material level. Full details from the research project
formulated a fiber element to model nonlinear shear                      can be found in Jiang and Kurama (2009).
deformations in RC structures. The development of the fiber
wall model in this paper is fundamentally the same as the                                       BACKGROUND
microplane formulation in Petrangeli et al. (1999), with a                 Previous research on the modeling of RC walls, including
simplifying m
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