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CONTENTS
Volume 36, Number 4, November10 2010
 

Abstract
This paper focuses on the development, verification and application of a three-dimensional nite element code for coupled thermal and structural analysis of roller compacted concrete arch dams. The Ostour Arch dam located on Ghezel-Ozan River, Iran, which was originally designed as conventional concrete arch dam, has been taken for the purpose of verication of the nite element code. In this project, RCC technology has been ascertained as an alternative method to reduce the cost of the project and make it competitive. The thermal analysis has been carried out taking into account the simulation of the sequence of construction, environmental temperature changes, and the wind speed. In addition, the variation of elastic modulus with time has been considered in this investigation using Concard\'s model. An attempt was made to compare the stresses developed in the dam body five years after the completion of the dam with those of end of the construction. It was seen that there is an increase in the tensile stresses after five years over stresses obtained immediately at the end of construction by 61.3%.

Key Words
arch RCC dam; thermal analysis; stress analysis; finite element modeling.

Address
Khaled H. Bayagoob: Civil Engineering Department, Universiti Putra Malaysia, 43400 UPM-Serdang, Malaysia
Jamaloddin Noorzaei: Institute of Advance Technology, Universiti Putra Malaysia, 43400 UPM-Serdang, Malaysia
Aeid A. Abdulrazeg: Civil Engineering Department, Universiti Putra Malaysia, 43400 UPM-Serdang, Malaysia
Awad A. Al-Karni: Civil Engineering Department, King Saud University, Riyadh, Saudi Arabia
Mohd Saleh Jaafar: Civil Engineering Department, Universiti Putra Malaysia, 43400 UPM-Serdang, Malaysia

Abstract
In this paper the formulation of an efficient frame element applicable for nonlinear analysis of 3D reinforced concrete (RC) frames is outlined. Interaction between axial force and bending moment is considered by using the fibre element approach. Further, section warping, effect of normal and tangential forces on the torsional stiffness of section and second order geometrical nonlinearities are included in the model. The developed computer code is employed for nonlinear static analysis of RC sub-assemblages and a simple approach for extending the formulation to dynamic cases is presented. Dynamic progressive collapse assessment of RC space frames based on the alternate path method is undertaken and dynamic load factor (DLF) is estimated. Further, it is concluded that the torsional behaviour of reinforced concrete elements satisfying minimum standard requirements is not significant for the framed structures studied.

Key Words
concrete structures; dynamic analysis; frame; progressive collapse; softening.

Address
Hamid R. Valipour: School of Civil and Environmental Engineering, University of Technology (UTS), Sydney, Australia
Stephen J. Foster: School of Civil and Environmental Engineering, The University of New South Wales (UNSW),
Sydney, Australia

Abstract
Fiber reinforced polymer (FRP) bars have been widely used as reinforcement for concrete structures. However, under elevated temperatures, the difference between the transverse coefficients of thermal expansion of FRP rebars and concrete may cause the splitting cracks of the concrete cover. As a result, the bonding of FRP-reinforced concrete may not sustain its function to transfer load between the FRP rebar and the surrounding concrete. The current study investigates the cracking resistance of FRP reinforced concrete against the thermal expansion based on a mechanical model that accounts for the tensile softening behavior of concrete. To evaluate the efficacy of the proposed model, the critical temperature increments at which the splitting failure of the concrete cover occurs and the internal crack radii estimated are compared with the results obtained from the previous studies. Simplified equations for estimating the critical temperature increments and the minimum concrete cover required to prevent concrete splitting failure for a designated temperature increment are also derived for design purpose.

Key Words
thermal expansion; splitting crack; FRP reinforced concrete; tensile softening.

Address
Pattamad Panedpojamana: Department of Civil Engineering, Chulalongkorn University, Phayathai Road, Pathumwan, Bangkok 10330, Thailand
Thanyawat Pothisiri: Department of Civil Engineering, Chulalongkorn University, Phayathai Road, Pathumwan, Bangkok 10330, Thailand

Abstract
Based on damage accumulation of multi-grid composite walls, a method of dynamic reliability estimations is proposed. The multi-grid composite wall is composed of edge frame beam, edge frame columns, grid beams, grid columns and filling blocks. The equations including stiffness, shear forces at filling blocks cracking and multi-grid composite walls yielding, ultimate displacement, and damage index are obtained through tests of 13 multi-grid composite wall specimens. Employing these equations in reliability calculations, procedures of dynamic reliability estimations based on damage accumulation of multi-grid composite walls subjected to random earthquake excitations are proposed. Finally the proposed method is applied to the typical composite wall specimen subjected to random earthquake excitations which can be specified by a finite number of input random variables. The dynamic reliability estimates, when filling blocks crack under earthquakes corresponding to 63% exceedance in 50 years and when the composite wall reach limit state under earthquakes corresponding to 2-3% exceedance in 50 years, are obtained using the proposed method by taking damage indexes as thresholds. The results from the proposed method which show good agreement with those from Monte-Carlo simulations demonstrate the proposed method is effective.

Key Words
dynamic reliability; damage accumulation; multi-grid composite walls; damage index; random earthquake excitation.

Address
Pei Liu: School of Civil Engineering, Beijing Jiaotong University, Beijing, 100044, China
Qian-Feng Yao: School of Civil Engineering, Beijing Jiaotong University, Beijing, 100044, China

Abstract
The shaking table tests were conducted on two small-scale models (Model 1 and Model 2) to examine the earthquake-induced damage of a concrete gravity dam, which has been planned for the construction with the recommendation of the peak ground acceleration of the maximum credible earthquake of 0.42 g. This study deals with the numerical simulation of shaking table tests for two smallscale dam models. The plastic damage constitutive model is used to simulate the crack/damage behavior of the bentonite-concrete mixture material. The numerical results of the maximum failure acceleration and the crack/damage propagation are compared with experimental results. Numerical results of Model 1 showed similar crack/damage propagation pattern with experimental results, while for Model 2 the similar pattern was obtained by considering the modulus of elasticity of the first and second natural frequencies. The crack/damage initiated at the changing point in the downstream side and then propagated toward the upstream side. Crack/damage accumulation occurred in the neck area at acceleration amplitudes of around 0.55 g~0.60 g and 0.65 g~0.675 g for Model 1 and Model 2, respectively.

Key Words
numerical simulation; concrete gravity dam; shaking table test; plastic damage model; earthquake.

Address
B. Phansri: School of Engineering & Technology, Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand
S. Charoenwongmit: School of Engineering & Technology, Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand
P. Warnitchai: School of Engineering & Technology, Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand
D.H. Shin: Head Researcher, Korea Water Resources Corporation, Daejeon, Korea
K.H. Park: School of Engineering & Technology, Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand

Abstract
This paper examines the ice cover effects on the seismic response of concrete gravity damreservoir-foundation interaction systems subjected to a horizontal earthquake ground motion. ANSYS program is used for finite element modeling and analyzing the ice-dam-reservoir-foundation interaction system. The ice-dam-reservoir interaction system is considered by using the Lagrangian(displacementbased) fluid and solid-quadrilateral-isoparametric finite elements. The Sar yar concrete gravity dam in Turkey is selected as a numerical application. The east-west component of Erzincan earthquake, which occurred on 13 March 1992 in Erzincan, Turkey, is selected for the earthquake analysis of the dam. Dynamic analyses of the dam-reservoir-foundation interaction system are performed with and without ice cover separately. Parametric studies are done to show the effects of the variation of the length, thickness, elasticity modulus and density of the ice-cover on the seismic response of the dam. It is observed that the variations of the length, thickness, and elasticity modulus of the ice-cover influence the displacements and stresses of the coupled system considerably. Also, the variation of the density of the ice-cover cannot produce important effects on the seismic response of the dam.

Key Words
concrete gravity dam; ice cover; fluid-structure interaction; earthquakes response; finite element method; Lagrangian approach.

Address
K. Haciefendioglu: Department of Civil Engineering, Ondokuz May s University, Samsun, Turkey
A. Bayraktar: Department of Civil Engineering, Ondokuz May s University, Samsun, Turkey
T. Turker: Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkey

Abstract
This paper presents a three-dimensional finite element method based structural analysis model for structural analysis of reinforced concrete high-rise buildings during construction. The model considered the time-dependency of the structural configuration and material properties as well as the effect of the construction rate and shoring stiffness. Uniaxial compression tests of young concrete within 28 days of age were conducted to establish the time-dependent compressive stress-strain relationship of concrete, which was then used as input parameters to the structural analysis model. In-situ tests of a RC high-rise building were conducted, the results of which were used for model verification. Good agreement between the test results and model predictions was achieved. At the end, a parametric study was conducted using the verified model. The results indicated that the floor position and construction rate had significant effect on the shore load, whereas the influence of the shore removal timing and shore stiffness have much smaller. It was also found that the floors are more prone to cracking during construction than is ultimate bending failure.

Key Words
high-rise building; reinforced concrete structure; construction safety; young concrete; timedependent analysis.

Address
Xiaobin Song: Department of Building Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, P.R. China
Xianglin Gu: Department of Building Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, P.R. China
Weiping Zhang: Department of Building Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, P.R. China
Tingshen Zhao: Department of Civil Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, P.R. China
Xianyu Jin: Department of Civil Engineering, Zhejiang University, 388 Yuhangtang Road, Hangzhou, 310058, P.R. China


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