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Volume 12, Number 3, September 2001

The three-dimensional behavior of confined concrete was investigated, including strength
enhancement due to triaxial compressive stresses, lateral expansion, compression softening, cover spalling
and post-peak ductility. A finite element program based on a nonlinear elasticity methodology was
employed to evaluate the ability to model triaxial behavior of reinforced concrete (RC) by combining
constitutive models proposed by several researchers. The capability of compression field based models to
reproduce the softening behavior of lightly cracked confined concrete was also investigated. Data from
tested specimens were used to evaluate the validity of the formulations. Good agreement with the
experimental results was obtained.

Key Words
nonlinear; finite element; analysis; reinforced concrete; confinement; lateral expansion; columns.

E. Montoya, F.J. Vecchio and S.A. Sheikh, Department of Civil Engineering, University of Toronto, Toronto, Canada

Current seismic design provisions allow structures to deform into inelastic range during
design level earthquakes since the chance to meet such event is quite rare. For this purpose, design base
shear is defined in current seismic design provisions as the value of elastic seismic shear force divided by
strength reduction factor, R (

Key Words
P-D effect; strength reduction factor; ductility factor.

Sang Whan Han, Oh-Sung Kwon and Li-Hyung Lee, Department of Architectural Engineering, Hanyang University, Seoul 133-791, Korea

Transient and quasi-steady-state vertical vibrations of a multi-span beam steel bridge located
on a single-track railway line are considered, induced by a superfast passenger train, moving at speed
120-360 km/h. Matrix dynamic equations of motion of a simplified model of the system are formulated
partly in the implicit form. A recurrent-iterative algorithm for solving these equations is presented.
Excessive vibrations of the system in the resonant zones are reduced effectively with passive dynamic
absorbers, tuned to the first mode of a single bridge span. The dynamic analysis has been performed for a
series of types of bridges with span lengths of 10 to 30 m, and with parameters closed to multi-span
beam railway bridges erected in the second half of the 20 th century.

Key Words
railway bridge; multi-span bridge; beam steel bridge; superfast train; moving load; transient vibrations; quasi-steady-state vibrations; passive dynamic absorbers; vibration control.

M. Klasztorny, Institute of Mechanics and Design, Warsaw University of Technology, Warsaw 02524, Poland

The postbuckling behaviour of thin plates is an important phenomenon in the design of thin
plated structures. In reality plates possess small imperfections and the behaviour of such imperfect plates
is of great interest. To numerically study the postbuckling behaviour of imperfect plates explicit
incremental or secant matrices have been presented in this paper. These matrices can be used in
combination with any thin plate element. The secant matrices are shown to be very accurate in tracing the
postbuckling behaviour of thin plates.

Key Words
postbuckling behaviour, imperfect plates, nonlinear finite element analysis, secant or incremental matrices.

S. Arul Jayachandran, Structural Engineering Research Centre, CSIR Campus, Taramani, Chennai-600 113, India
S. Gopalakrishnan, Indian Institute of Science, Bangalore-560 012, India
R. Narayanan, Structural Engineering Research Centre, CSIR Campus, Taramani, Chennai-600 113, India

The accurate finite element (FE) simulation of reinforced concrete (RC) slabs, having different
boundary conditions and subjected to uniformly distributed loading, has led to the use of the developed
FE models for generating results of ultimate loads from predictions of

Key Words
knowledge-based system; finite element method; RC slabs; material modeling; codes-of-practice; numerical predictions.

K.M.A. Hossain, Department of Civil Engineering, The Papua New Guinea University of Technology, Private Mail Bag, Lae, Papua New Guinea
O.O.R. Famiyesin, Department of Engineering, University of Aberdeen, Aberdeen AB24 3UE, UK

A multi-span bridge has the peak value of resultant girder moment or membrane stress at the
interior support. In this paper, the spline finite strip method (FSM) is modified to obtain the more
appropriate solution at the interior support where the peak values of solution exist. The modification has
been achieved by expressing the shape function with non-periodic B-splines which have multiple knots at
the boundary. The modified B-splines have the useful feature for interpolating the curve with sudden
change in curvature. Moreover, the modified spline FSM is very efficient in analyzing multi-span box
girder bridges, since a bridge can be modeled by an assembly of strips extended along the entire bridge
length. Numerical examples of the bridge analysis have been performed to verify the efficiency and
accuracy of the new spline FSM.

Key Words
finite strip; non-periodic B-spline function; multi-span bridge.

C.K. Choi, Department of Civil Engineering, KAIST, Daejeon 305-701, Korea
H.S. Hong, Structural Division, Chungsuk Engineering Co., Seoul 137-809, Korea

The present paper deals with the effective slenderness ratio of telescopic cylinders as a long
column having different cross sections. Firstly, the slenderness ratio defined in the current standard for the
telescopic cylinders is discussed to point out some difficulties which arise when the ratio is applied to the
column having different cross sections. Secondly, a new effective slenderness ratio is proposed for columns
having different cross sections by introducing a partial effective slenderness ratio. Finally, the proposed
slenderness ratio is applied, for extending and development of discussion, to a two-staged column having
piece-wise constant cross sections and a cylindrical column having linearly varying diameters.

Key Words
column; telescopic cylinder; buckling; slenderness ratio; partial effective slenderness ratio; cylinder-column; two-staged column.

Yoshihiko Sugiyama and Takamitsu Ohtomo, Department of Aerospace Engineering, Osaka Prefecture University, 1-1 Gakuen-chou, Sakai-shi 599-8531, Japan

Near source earthquakes can be characterized not only by strong horizontal but also by
strong vertical ground motions with broad range of dominant frequencies. The inelastic horizontal
response of thin-walled L-shaped steel bridge piers, which are popularly used as highway bridge supports,
subjected to simultaneous horizontal and vertical ground excitations of near source earthquakes is
investigated. A comprehensive damage index and an evolutionary-degrading hysteretic model are applied.
Numerical analysis reveals that the strong vertical excitation of a near source earthquake exerts
considerable influences on the damage development and horizontal response of thin-walled L-shaped steel
bridge piers.

Key Words
near source earthquakes; strong vertical ground motion; thin-walled steel bridge piers; inelastic response; damage index; evolutionary-degrading hysteretic model.

Guanmo Xie, Department of Engineering Mechanics, Wuhan University of Technology, Wuhan 430070, China
Takeo Taniguchi and Nawawi Chouw, Department of Environmental and Civil Engineering, Okayama University, Okayama 700-8530, Japan

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