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CONTENTS
Volume 47, Number 5, September10 2013
 

Abstract
Seismic response of two dimensional liquid tanks is numerically simulated using fully nonlinear velocity potential theory. Galerkin-weighted-residual based finite element method is used for solving the governing Laplace equation with fully nonlinear free surface boundary conditions and also for velocity recovery. Based on mixed Eulerian-Lagrangian (MEL) method, fourth order explicit Runge-Kutta scheme is used for time integration of free surface boundary conditions. A cubic-spline fitted regridding technique is used at every time step to eliminate possible numerical instabilities on account of Lagrangian node induced mesh distortion. An artificial surface damping term is used which mimics the viscosity induced damping and brings in numerical stability. Four earthquake motions have been suitably selected to study the effect of frequency content on the dynamic response of tank-liquid system. The nonlinear seismic response vis-a-vis linear response of rectangular liquid tank has been studied. The impulsive and convective components of hydrodynamic forces, e.g., base shear, overturning base moment and pressure distribution on tank-wall are quantified. It is observed that the convective response of tank-liquid system is very much sensitive to the frequency content of the ground motion. Such sensitivity is more pronounced in shallow tanks.

Key Words
seismic response; frequency content; artificial damping; quantification; mixed Eulerian-Lagrangian

Address
Santosh Kumar Nayak and Kishore Chandra Biswal : Department of Civil Engineering, National Institute of Technology Rourkela, Odisha, India

Abstract
The fiber-reinforced polymer (FRP) composite panel, with the benefits of light weight, high strength, good corrosion resistance, and long-term durability, has been considered as one of the prosperous alternatives for structural retrofits and replacements. Although with these advantages, a further application of FRPs in bridge engineering may be restricted, and that is partly due to some unsatisfied thermal performance observed in recent studies. In this regard, Kansas Department of Transportation (DOT) conducted a field monitoring program on a bridge with glass FRP (GFRP) honeycomb hollow section sandwich panels. The temperatures of the panel surfaces and ambient air were measured from December 2002 to July 2004. In this paper, the temperature distributing behaviors of the panels are firstly demonstrated and discussed based on the field measurements. Then, a numerical modeling procedure of temperature fields is developed and verified. This model is capable of predicting the temperature distributions with the local environmental conditions and material\'s thermal properties. Finally, a parametric study is employed to examine the sensitivities of several temperature influencing factors, including the hollow section configurations, environmental conditions, and material properties.

Key Words
FRP panel; thermal effect; bridge; temperature change; modeling

Address
B. Kong, C.S. Cai and F. Pan : Department of Civil and Environmental Engineering, Louisiana State University, 3418 Patrick Taylor Hall, Nicholson Extension Dr., Baton Rouge, 70803 LA, USA

Abstract
In the present work, the capacity ratings of steel truss bridges have been carried out incorporating dynamic effect of moving vehicles and its accumulating effect as fatigue. Further, corrosion in the steel members has been taken into account to examine the rating factor. Dynamic effect has been considered in the rating procedure making use of impact factors obtained from simulation studies as well as from codal guidelines. A steel truss bridge has been considered to illustrate the approach. Two levels of capacity ratings- the upper load level capacity rating (called operating rating) and the lower load level capacity rating (called inventory rating) were found out using Load and Resistance Factor Design (LRFD) method and a proposal has been made which incorporates fatigue in the rating formula. Random nature of corrosion on the steel member has been taken into account in the rating by considering reduced member strength. Partial safety factor for each truss member has been obtained from the fatigue reliability index considering random variables on the fatigue parameters, traffic growth rate and accumulated number of stress cycle using appropriate probability density function. The bridge has been modeled using Finite Element software. Regressions of rating factor versus vehicle gross weight have been obtained. Results show that rating factor decreases when the impact factor other than those in the codal provisions are considered. The consideration of fatigue and member corrosion gives a lower value of rating factor compared to those when both the effects are ignored. In addition to this, the study reveals that rating factor decreases when the vehicle gross weight is increased.

Key Words
steel truss bridge; operating rating; inventory rating; Load and Resistance Factor Design; fatigue; traffic growth rate

Address
R. Lalthlamuana and S. Talukdar : Department of Civil Engineering, Indian Institute of Technology Guwahati-781039, India

Abstract
As a new type of vibration reduction, the ladder track system has been successfully used in engineering. In this paper, a numerical model of the train-track-viaduct system is established to study the dynamic responses of an elevated bridge with ladder track. The system is composed of a vehicle submodel, a track submodel and a bridge submodel, with the measured track irregularities as the system self-excitation. The whole time histories of a train running through an elevated bridge with 3x27m continuous PC box girders are simulated. The dynamic responses of the bridge such as deflections, lateral and vertical accelerations, and the vehicle responses such as derailment factors, offload factors and car-body accelerations are calculated. The calculated results are partly validated through the comparison with the experimental data. Compared to the common slab track, adapting the ladder sleeper can effectively reduce the accelerations of the bridge girder, and also reduce the car-body accelerations and offload factors of the train vehicle.

Key Words
ladder track; elevated bridge; vibration isolation; numerical simulation; dynamic response

Address
He Xia : School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China; Department of Civil Engineering, KU Leuven, B 3001 Leuven, Belgium
Yushu Deng : School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China; Department of Civil Engineering, KU Leuven, B 3001 Leuven, Belgium; CCCC Railway Consultants Co. Ltd., Beijing, China
Chaoyi Xia : School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China; Department of Civil Engineering, KU Leuven, B 3001 Leuven, Belgium
G. De Roeck : Department of Civil Engineering, KU Leuven, B 3001 Leuven, Belgium
Lin Qi : TESS Corporation Ltd., Tokyo, Japan
Lu Sun : School of Transportation, Southeast University, Nanjing 210018, China

Abstract
Two new predictive design methods are presented in this study. The first is a hybrid method, called neuro-fuzzy, based on neural networks with fuzzy learning. A total of 280 experimental datasets obtained from the literature concerning concentric punching shear tests of reinforced concrete slab-column connections without shear reinforcement were used to test the model (194 for experimentation and 86 for validation) and were endorsed by statistical validation criteria. The punching shear strength predicted by the neuro-fuzzy model was compared with those predicted by current models of punching shear, widely used in the design practice, such as ACI 318-08, SIA262 and CBA93. The neuro-fuzzy model showed high predictive accuracy of resistance to punching according to all of the relevant codes. A second, more userfriendly design method is presented based on a predictive linear regression model that supports all the geometric and material parameters involved in predicting punching shear. Despite its simplicity, this formulation showed accuracy equivalent to that of the neuro-fuzzy model.

Key Words
punching shear strength; slab-column connection; neuro-fuzzy system; size effect; linear regression; meta-heuristics method

Address
Mariam Hafidi, Fattoum Kharchi : Houari Boumedienne University (USTHB), Civil Engineering Faculty, Laboratory of Built in Environment (LBE), Bp 32 Bab Ezzouar 16111 Alger, Algeria
Abdelouhab Lefkir : Polytechnic National School (ENP), laboratory of construction and environment (LCE), 10, Avenue Hassen Badi EL Harrach, 16182, Alger, Algeria

Abstract
People started to replace natural aggregate with recycled aggregate for a number of years due to disposal problem and certain other potential benefits. Though there are number of drawbacks with use of recycled aggregates like lesser modulus of elasticity, low compressive strength, increase in shrinkage, there are results of earlier studies that use of chemical and mineral admixtures improves the strength and durability of recycled concrete. The use of recycled aggregate from construction and demolition wastes is showing prospective application in construction as alternative to natural aggregates. It conserves lot of natural resources and reduces the space required for the landfill disposal. In the present research work, the effect of recycled aggregate on strength and durability aspects of concrete is studied. Grade of concrete chosen for the present work is M50 (with a characteristic compressive strength of 50 MPa). The recycled aggregates were collected from demolished structure with 20 years of age. Natural Aggregate (NA) was replaced with Recycled Aggregate (RA) in different percentages such as 25, 50 and 100 to understand its effect. The experiments were conducted for different ages of concrete such as 7, 14, 28, 56 days to assess the compressive and tensile strength. Durability characteristics of recycled aggregate concrete were studied with Rapid chloride penetration test (as per ASTMC1202), sorptivity test and acid test to assess resistance against chloride ion penetration, capillary suction and chemical attack respectively. Mix design for 50 MPa gives around 35 MPa after replacing natural aggregate with recycled aggregate in concrete mix and the chloride penetration range also lies in moderate limit. Hence it is understood from the results that replacement of NA with RA is very much possible and will be ecofriendly.

Key Words
natural aggregate; recycled aggregate; recycled aggregate concrete; compressive strength; tensile strength; Rapid chloride penetration test (RCPT); Sorptivity test

Address
Palaniraj Saravanakumar and Govindasamy Dhinakaran : School of Civil Engineering, SASTRA University, Thanjavur 613401, India

Abstract
In current study, natural frequency response of fiber metal laminated (FML) fibrous composite panels is optimized under different combination of the three classical boundary conditions using particle swarm optimization (PSO) algorithm and finite strip method (FSM). The ply angles, numbers of layers, panel length/width ratios, edge conditions and thickness of metal sheets are chosen as design variables. The formulation of the panel is based on the classical laminated plate theory (CLPT), and numerical results are obtained by the semi-analytical finite strip method. The superiority of the PSO algorithm is demonstrated by comparing with the simple genetic algorithm.

Key Words
fiber metal laminated panel; particle swarm optimization algorithm; fundamental frequency

Address
H. Ghashochi-Bargh and M.H. Sadr: Aerospace Engineering Department, Centre of Excellence in Computational Aerospace Engineering, Amirkabir University of Technology, Hafez Avenue, Tehran, Iran

Abstract
This paper addresses the structural design of the front end of Siemens ER24 locomotive body. The steel structure of the frontend is replaced with composite. Optimization of the composite lay-up is performed using Genetic Algorithms. Initially an optimized single design for the entire structure is presented. Then a more refined optimum is developed by considering the separate optimization of 7 separate regions of the structure. Significant savings in the weight of the structure are achieved.

Key Words
composite frontend; optimization; genetic algorithm; locomotive; buckling

Address
S.M. Rohani, A. Vafaeesefat : Department of Mechanical Engineering, Faculty of Engineering, Imam Hossein University, Tehran, Iran
M. Esmkhani, M. Partovi and H.R. Molladavoudi : Engineering Department, Mapnalocomotive Company, MAPNA Group, 1968657113, Karaj, Iran


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