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CONTENTS
Volume 17, Number 2, February 2004
 

Abstract
The bonding behaviors of Lightweight Aggregate Concrete (LWAC) and normal weight concrete were investigated experimentally. Pull-out tests were carried out to measure the bond strengths of three groups of specimens with compressive strength levels of 60, 40, and 20 MPa, respectively. Test results showed that the difference in the bond failure pattern between LWAC and normal weight concrete was significant as the concrete compressive strength became lower than 40 MPa. The corresponding bond strengths of LWAC were lower than that for normal weight concrete. As the compressive strength of concrete became relatively high (> 40 MPa), a bond failure pattern in normal weight concrete occurred that was similar to that in LWAC. The bond strength of LWAC is higher than that for normal weight concrete because it possesses higher mortar strength. Stirrup use leads to an increase of approximately 20% in nominal bond strength for both types of concrete at any strength level.

Key Words
lightweight concrete; bond strength; concrete strength; mortar strength.

Address
Department of Civil Engineering, National Chung-Hsing University,
Taichung 40227, Taiwan

Abstract
An elasticity solution for sandwich plates assembled with non-rigid bonding and subjected to edgewise loads is presented. The solution satisfies the equilibrium equations of the face and core elements, the compatibility equations of stresses and strains at the interfaces, and the boundary conditions. To investigate the effects of bonding stiffnesses on the responses of sandwich plates, numerical evaluations are conducted. The results obtained have shown that the bonding stiffness, up to a certain level, has a strong effect on the plate mechanical response. Beyond this level, the usual assumption of perfect bonding used in classical theories is quite acceptable. An answer to what constitutes perfect bonding is found in terms of the ratio of the core stiffness to the bonding stiffness.

Key Words
composites; deformation; edge loads; interlayer shear; orthotropic; panels; plates; sandwich; stiffness; strain; stress.

Address
P.O. Box 35744, Syracuse, NY 13210, USA

Abstract
The design load-carrying capacities of wooden shores depend on factors, such as the wood species and properties, and construction methods. This paper focuses on the construction methods, including an upright single shore, group of upright shores, group of inclined shores, butt connections and lap connections. This paper reports experiments to obtain critical loads and then developed an empirical equation based on Euler\' formula for the critical loads and design load-carrying capacities. The test results show that the critical loads for an upright single wooden shore are greater than the average values for a group of upright shores, and the latter are greater than the average values for a group of inclined shores. Test results also show that the critical loads become smaller when butt or lap connections are used, butt connections possessing greater critical loads than lap connections. Groups of inclined shores are very popular at work sites because they have some practical advantages even though they actually possess inferior critical loads. This paper presents an improved setup for constructing groups of inclined shores. With this method, the inclined shores have larger critical loads than upright shores. The design load-carrying capacities were obtained by multiplying the average critical loads by a resistance factor (or strength reduction factor, f ) that were all smaller than 1. This article preliminarily suggests f factors based on the test results for the reference of engineers or specification committees.

Key Words
wooden shores; load-carrying capacity; construction.

Address
Department of Civil Engineering, Chung Hsing University, Taichung, 40227 Taiwan, R.O.C.

Abstract
A shaking table test on a three-story one-bay steel frame model with metallic yield dampers and their parallel connection with oil dampers is carried out to study the dynamic characteristics and seismic performance of the energy dissipation system. It is found from the test that the combined energy dissipation system has favorable reducing vibration effects on structural displacement, and the structural peak acceleration can not evidently be reduced under small intensity seismic excitations, but in most cases the vibration reduction effect is very good under large intensity seismic excitations. Test results also show that stiffness of the energy dissipation devices should match their damping. Dynamic analysis method and mechanics models of these two dampers are proposed. In the analysis method, the force-displacement relationship of the metallic yield damper is represented by an elastic perfectly plastic model, and the behavior of the oil damper is simulated by a velocity and displacement relative model in which the contributions of the oil damper to the damping force and stiffness of the system are considered. Validity of the analytical model and the method is verified through comparison between the results of the shaking table test and numerical analysis.

Key Words
metallic yield damper; oil damper; combined energy dissipation system; analysis model; shaking table test.

Address
Qiang Zhou
Institute of Civil Engineering and Architecture, Wuhan University of Technology,
Wuhan, 430070, P.R. China

Xilin Lu
State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University,
Shanghai, 200092, P.R. China

Abstract
The dynamic response characteristics of a rectangular fluid container are investigated by using finite element method. The fluid is assumed to be linear-elastic, inviscid and compressible. A displacement-based fluid finite element was employed to allow for the effects of the fluid. A typical rectangular fluid container, which is used in recent studies, is considered for the numerical analysis. The North-South component of El Centro Earthquake records is used as input ground acceleration. Rigid and flexible fluid containers solutions are obtained for the chosen sample tank. Hydrodynamic pressures and sloshing motions are determined using Lagrangian fluid finite element. The results obtained from this study are compared with the results obtained by boundary-finite element method (BEM-FEM) and requirements of Eurocode-8. Based on the numerical analysis, some conclusions and discussions on the design considerations for rectangular fluid containers are presented.

Key Words
rectangular fluid containers; seismic design; finite element method; EC-8.

Address
Karadeniz Technical University, Department of Civil Engineering, Trabzon, Turkey

Abstract
There is an ever-increasing demand for assessment of earthquake effects on transportation structures, emphasised by the crippling consequences of recent earthquakes hitting developed countries reliant on road transportation. In this work, vulnerability functions for RC bridges are derived analytically using advanced material characterisation, high quality earthquake records and adaptive inelastic dynamic analysis techniques. Four limit states are employed, all based on deformational quantities, in line with recent development of deformation-based seismic assessment. The analytically-derived vulnerability functions are then compared to a data set comprising observational damage data from the Northridge (California 1994) and Hyogo-ken Nanbu (Kobe 1995) earthquakes. The good agreement gives some confidence in the derived formulation that is recommended for use in seismic risk assessment. Furthermore, by varying the dimensions of the prototype bridge used in the study, and the span lengths supported by piers, three more bridges are obtained with different overstrength ratios (ratio of design-toavailable base shear). The process of derivation of vulnerability functions is repeated and the ensuing relationships compared. The results point towards the feasibility of deriving scaling factors that may be
used to obtain the set of vulnerability functions for a bridge with the knowledge of a

Key Words
vulnerability functions; RC bridges; seismic response; damage assessment

Address
A.S. Elnashai
CEE Dept., 205 North Mathews Ave., University of Illinois at Urbana-Champaign,
Urbana, Illinois 61801, USA

B. Borzi
EQE International Ltd., UK

S. Vlachos
Thomi Engineering, Athens, Greece

Abstract
Incremental launching method is one of the highly competitive techniques for construction of concrete bridges. It avoids costly and time consuming form work and centralizes all construction activities in a small casting yard, thus saving in cost and time against conventional bridge construction. From the quality point of view, it eliminates the uncertainty of monolithic behaviour by allowing high repetitiveness and industrial environment. But, from analysis and design point of view, the most characteristic aspect of incrementally launched bridges is that, it has to absorb the stresses associated with the temporary supports that are gradually taken on by the deck during its launch. So, it is necessary to analyse the structure for each step of launching which is a tedious and time consuming process. Effect of support settlements or temperature variation makes the problem more complex. By using transfer matrix method, this problem can be handled efficiently with minimal computational effort. This paper gives insight into method of analysis, formulation for optimization of the structural system, effect of support settlement and temperature gradient, during construction, on the stress state of incrementally launched bridges.

Key Words
incrementally launched continuous bridge; construction phase analysis; transfer matrix; optimisation; thermal analysis; settlement analysis; launching nose; nose-deck interaction; length ratio; load ratio; stiffness ratio.

Address
Structural Engineering Research Centre, CSIR Campus, Taramani, Chennai-600113, India

Abstract
This paper presents an improved Monte Carlo simulation for the probabilistic determination of initial cable forces of cable-stayed bridges under dead loads using the response surfaces method. A response surface (i.e. a quadratic response surface without cross-terms) is used to approximate structural response. The use of the response surface eliminates the need to perform a deterministic analysis in each simulation loop. In addition, use of the response surface requires fewer simulation loops than conventional Monte Carlo simulation. Thereby, the computation time is saved significantly. The statistics (e.g. mean value, standard deviation) of the structural response are calculated through conventional Monte Carlo simulation method. By using Monte Carlo simulation, it is possible to use the existing deterministic finite element code without modifying it. Probabilistic analysis of a truss demonstrates the proposed method\' efficiency and accuracy; probabilistic determination of initial cable forces of a cable-stayed bridge under dead loads verifies the method\' applicability.

Key Words
cable-stayed bridges; initial cable forces; probabilistic; parametric uncertainties; response surface; Monte Carlo simulation; statistics.

Address
Jin Cheng and Ru-Cheng Xiao
Department of Bridge Engineering, Tongji University, Shanghai, 200092, China

Jian-Jing Jiang
Department of Civil Engineering, Tsinghua University, Beijing, 100084, China


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