Study of steel and composite shear walls for applications
in buildings with steel structure
Irena Hadzhiyaneva
Summary
The recent worldwide application of steel plate (SPSW) and composite steelreinforced concrete (CSW) shear walls and their complex structural behaviour has
challenged the author of the present dissertation thesis. The main scope of the study
was determined after analysis of the literature on this topic in Chapter One. The main
goals of research include (1) assessment of the available approximate numerical
methods for modeling of SPSWs and CSWs behaviour; (2) numerical and
experimental analysis of CSWs (with purposely made gap between the boundary steel
frame and RC encasement of the steel web panel), and (3) investigation of the semirigid frame joints on the global behaviour of the shear walls. For the purpose of the
experimental study two steel and one composite specimens (with 1:4 scale) having
identical dimensions of the steel components have been fabricated and tested. The
steel web panel is very slender and unstiffened by intermediate stiffeners (with
slenderness ratio equal to 400). The detailing of the semi-rigid frame joints was
chosen to be appropriate for upgrading of existing steel structures with low ductility.
The first steel specimen was subjected to monotonically increasing lateral load, while
the others were tested under cyclic pseudo-static lateral force till structural collapse.
The tests are described in Chapters Two and Three. For the numerical analyses both
2D FE-models (with lumped material nonlinearity) using the so-called method of
inclined strips and refined 3D FE-models (with distributed material nonlinearity)
were created. Nonlinear pushover analyses with lateral force applied along the beam
axis were conducted using SAP2000 for the 2D-models and ANSYS v.10 for the
3D-models. The modeling features are discussed in Chapter Four. The following
major conclusions were made in Chapter Five on the basis of comparisons of the
experimental, numerical and analytically-derived results:
 The approximate numerical methods demonstrated high reliability. The
inclined tension- and compression-strip approach used for composite shear walls
modeling, recently proposed by Sun et al. which is a generalization of the popular
tension-strip model of Thornburn, is a quick and easy way to predict the yield
resistance and complex wall behaviour. However, none of the methods predicted well
the initial stiffness of the specimens, giving unrealistically high values, a fact which
has been reported by other authors, too. From this point of view the truss models have
an additional advantage of being more flexible. The development of complex
nonlinear deformations and formation of plastic hinges in the semi-rigid frame joints
shall be included in their refined numerical or approximate analytical modeling. The
accurate definition of the „moment-rotation” relationship of these joints is a major
factor for the correct representation of the interaction between the various
components of the steel and composite shear walls and for the capacity design of
their boundary members and connections.
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 The conducted experimental program and numerical analysis have confirmed
the beneficial effect of the separation of the boundary steel frame and the reinforced
concrete web encasement on global CSW behaviour. The SPSWs demonstrated high
stiffness and ductility, but the CSW design based on the innovative proposal of
Astaneh-Asl leads to similar ductility and even better energy dissipation. An
additional factor for this favorable structural behaviour is resistance increasing of the
RC-cover and its shear stud connections to the slender steel web in order to ensure
continuous out-of-plane support of the steel web till the end of the test. Despite of
these measures local web buckling in-between the stud connectors was observed
during the last cycles of the test, which can be explained by some aspects of design
procedure and particular detailing of reinforced-concrete cover and stud connections.
The resulting reduction of the shear wall resistance has to be taken into account, as it
led to ultimate resistance for W3-specimen in-between the values predicted for the
SPSW- and CSW-specimens with the same dimensions.
 During the tests, the semi-rigid joints have showed adequate rotational
capacity according to requirements of AISC Seismic Provisions (2005) and Eurocode
8 (2005). The rigid frame joints for the boundary framing have optimal capacity,
ductility and energy dissipation for application of the steel and composite shear walls
in new buildings, but if adequately designed, detailed and executed, semi-rigid frame
joints could be appropriate alternative for seismic retrofit of existing buildings with
low ductility.
The scientific contributions of the dissertation thesis are summarized in
Chapter Six and the major directions planned for future research work on the topic
are given in Chapter Seven. The major research contributions include the assessment
of the approximate numerical methods, experimental proof of the favorable influence
of the separation (gap) between the RC web encasement and the boundary steel frame
on the CSW behaviour, determination of insufficiency in the code requirements for
structural design of RC-encasement and its shear stud connections to the steel web
panel, and finally, proof of adequate behaviour of the particular detail proposed for
the semi-rigid boundary frame joints. The future directions of research include
determination of reasons leading to early local buckling of steel web in-between the
shear stud connectors, refining of design provisions for composite shear walls, and
analysis of global structural behaviour of existing buildings with low-ductility
moment-resisting frames upgraded by inclusion of steel and composite shear walls.
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