Abstract
This paper is concerned with free vibration characteristics and natural frequency of horizontally
curved composite plate girder bridges. Three-dimensional finite element models are developed for the girders
using the software package LUSAS and analyses carried out on the models. The validity of the finite element
models is first established through comparison with the corresponding results published by other researchers.
Studies are then carried out to investigate the effects of total number of girders, number of cross-frames and
curvature on the free vibration response of horizontally curved composite plate girder bridges. The results
confirm the fact that bending modes are always coupled with torsional modes for horizontally curved bridge
girder systems. The results show that the first bending mode is influenced by composite action between the
concrete deck and steel beam at low subtended angle but, on the girders with larger subtended angle at the
centre of curvature such influence is non-existence. The increase in the number of girders results in higher
natural frequency but at a decreasing rate. The in-plane modes viz. longitudinal and arching modes are
significantly influenced by composite action and number of girders. If no composite action is taken into
account the number of girders has no significant effect for the in-plane modes.
Key Words
horizontally curved girders; composite girders; bridges, cross-frames; natural frequency;
finite element analysis.
Address
Department of Civil and Structural Engineering, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia
Abstract
According to the results of 9 circular concrete filled steel tube (CFT) push-out tests, a new
theoretical model for average bond stress versus free end slip curve is proposed. The relationship between
average bond stress and free end slip is obtained considering some varying influential parameters such as
slenderness ratio and diameter-to-thickness ratio. Based on measured steel tube strain and relative slip at
different longitudinal positions, the distribution of bond stress and relative slip along the length of steel tube is
obtained. An equation for predicting the varying bond-slip relationship along longitudinal length and a
position function reflecting the variation are proposed. The presented method can be used in the application of
finite element method to analyze the behavior of CFT structures.
Key Words
concrete filled steel tube; bond-slip; push-out test; constitutive relationship; position function.
Address
State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
Abstract
Ample research effort has been oriented into developing damage indices with the aim of estimating
in a reasonable manner the consequences, in terms of structural damage and deterioration, of severe plastic
cycling. Although several studies have been devoted to calibrate damage indices for steel and reinforced concrete
members; currently, there is a challenge to study and calibrate the use of such indices for the practical evaluation
of complex structures. The aim of this paper is to introduce an energy-based damage index for multi-degree-offreedom
steel buildings that accounts explicitly for the effects of cumulative plastic deformation demands. The
model has been developed by complementing the results obtained from experimental testing of steel members
with those derived from analytical studies regarding the distribution of plastic demands on several steel frames
designed according to the Mexico City Building Code. It is concluded that the approach discussed herein is a
promising tool for practical structural evaluation of framed structures subjected to large energy demands.
Address
Fac. de Ing., Universidad Autonoma de Sinaloa, Culiacan, Sinaloa, Mexico
Departamento de Materiales, Universidad Autonoma Metropolitana, Mexico City, Mexico
Instituto de Ingenieria, Universidad Nacional Autonoma de Mexico, Mexico City, Mexico
Abstract
Three dimensional free vibrations analysis of functionally graded fiber reinforced cylindrical shell
is presented, using differential quadrature method (DQM). The cylindrical shell is assumed to have continuous
grading of fiber volume fraction in the radial direction. Suitable displacement functions are used to reduce the
equilibrium equations to a set of coupled ordinary differential equations with variable coefficients, which can
be solved by differential quadrature method to obtain natural frequencies. The main contribution of this work
is presenting useful results for continuous grading of fiber reinforcement in the thickness direction of a
cylindrical shell and comparison with similar discrete laminate composite ones. Results indicate that significant
improvement is found in natural frequency of a functionally graded fiber reinforced cylinder due to the
reduction in spatial mismatch of material properties and natural frequency
Abstract
Enhancement in the seismic buckling capacity of steel tanks caused by the addition of fiber
reinforced polymers (FRP) retrofit layers attached to the outer walls of the steel tank is investigated. Threedimensional
non-linear finite element modeling is utilized to perform such analysis considering non linear
material properties and non-linear large deformation large strain analysis. FRP composites which possess high
stiffness and high failure strength are used to reduce the steel hoop stress and consequently improve the tank
capacity. A number of tanks with varying dimensions and shell thicknesses are examined using FRP composites
added in symmetric layers attached to the outer surface of the steel shell. The FRP shows its effectiveness in
carrying part of the hoop stresses along with the steel before steel yielding. Following steel yielding, the FRP
restrains the outward bulging of the tank and continues to resist higher hoop stresses. The percentage
improvement in the ultimate base moment capacity of the tank due to the addition of more FRP layers is
shown to be as high as 60% for some tanks. The percentage of increase in the tank moment capacity is shown
to be dependent on the ratio of the shell thickness to the tank radius (t/R). Finally a new methodology has been
explained to calculate the location of Elephant foot buckling and consequently the best location of FRP application.
Key Words
steel tanks; seismic design; finite element analysis; elephant
Address
Department of Engineering, Cairo University, Egypt
Steel Structures and Bridges, Structural Engineering Department, Cairo University, Egypt
Dean of Engineering American University, Cairo, Egypt.
