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CONTENTS
Volume 59, Number 2, July25 2016
 

Abstract
Integral bridges are typically designed with flexible foundations that include one row of piles. The construction of integral bridges solves difficulties due to the maintenance of expansion joints and bearings during serviceability. It causes integral bridges to become more economic comparing with conventional bridges. Research has been focused not only to enhance the seismic performance of newly designed bridges, but also to develop retrofit strategies for existing ones. The local performance of the pile to abutment connection will have a major effect on the performance of the structure and the embedment length of pile inside the abutment has a key role to provide shear and flexural resistance of pile-abutment connections. In this paper, a simple method was developed to estimate the initial value of embedment length of the pile for retrofitting of specimens. Four specimens of pile-abutment connections were constructed with different embedment lengths of pile inside the abutment to evaluate their performances. The results of the experimentation in conjunction with numerical and analytical studies showed that retrofitting pile-abutment connections with CFRP wraps increased the strength of the connection up to 86%. Also, designed connections with the proposed method had sufficient resistance against lateral load.

Key Words
integral bridge; steel pile-abutment connection; flexural strength of steel pile; embedment length of pile; retrofitting; CFRP

Address
Seyed Saeed Mirrezaei, Majid Barghian, Hossein Ghaffarzadeh and Masood Farzam: Department of Civil Engineering, University of Tabriz, 29 Bahman Blvd., Tabriz, Iran

Abstract
A circular plate with constant thickness, finite radius and stiff edge lying on an elastic halfspace is considered. The half-space consists of a soft functionally graded (FGM) layer with arbitrary varying elastic properties and a homogeneous elastic substrate. The plate bends under the action of arbitrary axisymmetric distributed load and response from the elastic half-space. A semi-analytical solution for the problem effective in whole range of geometric (relative layer thickness) and mechanical (elastic properties of coating and substrate, stiffness of the plate) properties is constructed using the bilateral asymptotic method (Aizikovich et al. 2009). Approximated analytical expressions for the contact stresses and deflections of the plate are provided. Numerical results showing the qualitative dependence of the solution from the initial parameters of the problem are obtained with high precision.

Key Words
plate bending; circular plate; Kirchhoff plate; axisymmetric problem; functionally graded; soft layer; elastic layer; analytic method

Address
Sergey S. Volkov: Research and Education Center \"Materials\", Don State Technical University, Rostov-on-Don 344000, Russia
Alexander N. Litvinenko: Vorovich Institute of Mathematics, Mechanics and Computer Science, Southern Federal University, Rostov-on-Don 344090, Russia
Sergey M. Aizikovich: Research and Education Center \"Materials\", Don State Technical University, Rostov-on-Don 344000, Russia; Vorovich Institute of Mathematics, Mechanics and Computer Science, Southern Federal University, Rostov-on-Don 344090, Russia
Yun-Che Wang: Department of Civil Engineering, National Cheng Kung University, Tainan 70101, Taiwan
Andrey S. Vasiliev: Research and Education Center \"Materials

Abstract
This research develops a finite element code for the transient dynamic analysis of tapered fiber reinforced polymer (FRP) poles with hollow circular cross-section and flexible joints used in power transmission lines. The FRP poles are modeled by tapered beam elements and their flexible joints by a rotational spring. To solve the time equations of transient dynamic analysis, precise time integration method is utilized. In order to verify the utilized formulations, a typical jointed FRP pole under step, triangular and sine pulses is analyzed by the developed finite element code and also ANSYS commercial finite element software for comparison. Thereafter, the effect of joint flexibility on its dynamic behavior is investigated. It is observed that by increasing the joint stiffness, the amplitude of the pole tip deflection history decreases, and the time of occurrence of the maximum deflection is earlier.

Key Words
transmission pole; fiber-reinforced; transient dynamic; finite element (FE); flexible joint

Address
Behnam Saboori: Center of Excellence in Experimental Solid Mechanics and Dynamics, School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846, Iran
Seyed Mohammad Reza Khalil: Center of Excellence for Research in Advanced Materials & Structures, Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Tehran, Iran; Faculty of Engineering, Kingston University, UK

Abstract
Effect of silica fume on fresh properties, compressive strength at 28 days and fracture behavior of fly ash concrete composite were studied in this paper. Test results indicated that the fluidity and flowability of fly ash concrete composites decreased and fly ash concrete composite are more cohesive and appear to be sticky with the addition of silica fume. Addition of silica fume was very effective in improving the compressive strength at 28 days of fly ash concrete composite, and the compressive strength of fly ash concrete composite has a trend of increase with the increase of silica fume content. Results also indicated that all the fracture parameters of effective crack length, fracture toughness, fracture energy, the critical crack opening displacement and the maximum crack opening displacement of fly ash concrete composite decreased with the addition of silica fume. When the content of silica fume increased from 3% to 12%, these fracture parameters decreased gradually with the increase of silica fume content. Furthermore, silica fume had great effect on the relational curves of the three-point bending beam specimen. As the silica fume content increased from 3% to 12%, the areas surrounded by the three relational curves and the axes were becoming smaller and smaller, which indicated that the capability of concrete composite containing fly ash to resist crack propagation was becoming weaker and weaker.

Key Words
fly ash concrete; fracture behavior; silica fume

Address
Peng Zhang, Ji-Xiang Gao, Xiao-Bing Dai, Tian-Hang Zhang and Juan Wang: School of Water Conservancy and Environment Engineering, Zhengzhou University, Zhengzhou, P.R. China

Abstract
This paper investigates the ground vibration induced by high-speed trains moving on multi-span continuous bridges. The dynamic impact factor of multi-span continuous bridges under trainloads was first determined in the parametric study, which shows that the dynamic impact factor will be large when the first bridge vertical natural frequency is equal to the trainload dominant frequencies, nV/D, where n is a positive integer, V is the train speed, and D is the train carriage interval. In addition, more continuous spans will produce smaller dynamic impact factors at this resonance condition. Based on the results of three-dimensional finite element analyses using the soil-structure interaction for realistic high-speed railway bridges, we suggest that the bridge span be set at 1.4 to 1.5 times the carriage interval for simply supported bridges. If not, the use of four or more-than-four-span continuous bridges is suggested to reduce the train-induced vibration. This study also indicates that the vibration in the train is major generated from the rail irregularities and that from the bridge deformation is not dominant.

Key Words
finite element analysis; high-speed train; impact factor; multi-span bridge; resonance; trainload dominant frequency; vibration

Address
S.H. Ju: Department of Civil Engineering, National Cheng-Kung University, Tainan City, Taiwan, R.O.C.

Abstract
Seismic performance evaluation of shear wall is essential as it is the major lateral load resisting member of a structure. The ultimate load and ultimate drift of the shear wall are the two most important parameters which need to be assessed experimentally and verified analytically. This paper comprises the results of monotonic tests, quasi-static cyclic tests and shake-table tests carried out on a midrise shear wall. The shear wall considered for the study is 1:5 scaled model of the shear wall of the internal structure of a reactor building. The analytical simulation of these tests is carried out using micro and macro modeling of the shear wall. This paper mainly consists of modification in the hysteretic macro model, developed for RC structural walls by Lestuzzi and Badoux in 2003. This modification is made by considering the stiffness degradation effect observed from the tests carried out and this modified model is then used for nonlinear dynamic analysis of the shear wall. The outcome of the paper gives the variation of the capacity, the failure patterns and the performance levels of the shear walls in all three types of tests. The change in the stiffness and the damping of the wall due to increased damage and cracking when subjected to seismic excitation is also highlighted in the paper.

Key Words
shear walls; shake table tests; quasi-static cyclic tests; analysis; damping

Address
Y.M. Parulekar, G.R. Reddy, R.K. Singh: Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai, 400085, India
N. Gopalkrishnan and G.V. Ramarao: Structural Engineering Research Centre, Chennai, 600113, India

Abstract
In this study the three-dimensional nonlinear finite element method was used to analyze the stresses distribution in the adhesive layer used to joint two Aluminum 2024-T3 adherends. We consider in this study the effect of different parameters witch directly affect the values of different stresses. The experimental design method is used to investigate the effects of geometrical parameters of the single lap joint in order to achieve an optimization of the assembly with simple lap joint. As a result, it can be said that both the geometrical modifications of the adhesive and adherends edge have presented a significant effect at the overlap edge thereby causing a decrease in peel and shear stresses. In addition, an analytical model is also given to predict in a simple but effective way the joint strength and its dependence on the geometrical parameters. This approach can help the designers to improve the quality and the durability of the structural adhesive joints.

Key Words
single lap joint; finite element analysis; stresses distribution; experimental design method

Address
M. Elhannani, K. Madani, M. Mokhtari: LMPM, Department of Mechanical Engineering, University of Sidi Bel- Abbes, Algeria
S. Touzain, X. Feaugas and S. Cohendoz: LaSIE, Laboratoire des Sciences de l\'Environnement, La Rochelle University, France

Abstract
This study addresses the effect of pre-stressed cables on a pre-stressed mega-braced steel frame through employing static analysis and pushover analysis. The performances of a pre-stressed mega-braced steel frame and a pure steel frame without mega-braces are compared in terms of base shear, ductility, and failure mode. The influence of the cable parameters is also analyzed. Numerical results show that cable braces can effectively improve the lateral stiffness of a pure frame. However, it reduces structural ductility and degenerates structural pre-failure lateral stiffness greatly. Furthermore, it is found that 20% fluctuation in the cable pretension has little effect on structural ultimate bearing capacity and lateral stiffness. As comparison, 20% fluctuation in the cable diameter has much greater impact.

Key Words
steel frame; pre-stressed mega-brace; pushover analysis; lateral stiffness; failure mode

Address
Tang Baijian, Zhang Fuxing, Wang Yi and Wang Fei: School of Civil Engineering and Architecture, Jiangsu University of Science and Technology, Mengxi Road, Zhenjiang 212003, China

Abstract
In this paper thermo-mechanical vibration analysis of a porous functionally graded (FG) Timoshenko beam in thermal environment with various boundary conditions are performed by employing a semi analytical differential transform method (DTM) and presenting a Navier type solution method for the first time. The temperature-dependent material properties of FG beam are supposed to vary through thickness direction of the constituents according to the power-law distribution which is modified to approximate the material properties with the porosity phases. Also the porous material properties vary through the thickness of the beam with even and uneven distribution. Two types of thermal loadings, namely, uniform and linear temperature rises through thickness direction are considered. Derivation of equations is based on the Timoshenko beam theory in order to consider the effect of both shear deformation and rotary inertia. Hamilton\'s principle is applied to obtain the governing differential equation of motion and boundary conditions. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of several parameters such as porosity distributions, porosity volume fraction, thermal effect, boundary conditions and power-low exponent on the natural frequencies of the FG beams in detail. It is explicitly shown that the vibration behavior of porous FG beams is significantly influenced by these effects. Numerical results are presented to serve benchmarks for future analyses of FG beams with porosity phases.

Key Words
thermo-mechanical vibration; functionally graded beam; porous material; DTM; thermal effect

Address
Farzad Ebrahimi and Ali Jafari: Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran

Abstract
During recent years researchers performed large effort to increase the service life and asphalt stability of the roads against traffic loads and weather conditions. Investigations carried out in various aspects such as changes in gradation, addition of various additives, changes in asphalt textures and etc. The objective of this research is to evaluate the advantages of adding recycled glass powder (RGP), Crumb Rubber (CR), styrene-butadiene rubber (SBR) and styrene butadiene styrene (SBS) to base bitumen with grade of 60/70 for modification of asphalt concrete. Initial studies conducted for determining the physical properties of bitumen and modifiers. A series of asphalt concrete samples made using various combinations of RGP, CR, SBR, SBS and base bitumen. All samples tested using Indirect Tensile Strength (ITS), Indirect Tensile Strength Modulus (ITSM) and Marshall Stability Tests. The new data compared with the results of control samples. The results showed that replacing RGP with known polymers improved ITS and ITSM results considerably. Also the Marshall Stability of modified mixtures using RGP is more than what is found for the base blend. Ultimately, the new RGP modifier had a huge impact on pavement performance and results in high flexibility which can be concluded as high service life for the new modified asphalt concrete.

Key Words
asphalt concrete; ITS; SBS; SBR; CR; RGP

Address
M. Pourabbas Bilondi, S.M. Marandi: Department of Civil Engineering, Shahid Bahonar University of Kerman, Kerman, Iran
F. Ghasemi: Department of Civil Engineering, Graduate University of Advanced Technology, Mahan, Kerman, Iran


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