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CONTENTS
Volume 50, Number 3, May10 2014
 

Abstract
This paper introduces a novel optimization technique based on gravitational search algorithm (GSA) for numerical optimization and multi-objective optimization of foundation. In the proposed method, a chaotic time varying system is applied into the position updating equation to increase the global exploration ability and accurate local exploitation of the original algorithm. The new algorithm called global-local GSA (GLGSA) is applied for optimization of some well-known mathematical benchmark functions as well as two design examples of spread foundation. In the foundation optimization, two objective functions include total cost and CO2 emissions of the foundation subjected to geotechnical and structural requirements are considered. From environmental point of view, minimization of embedded CO2 emissions that quantifies the total amount of carbon dioxide emissions resulting from the use of materials seems necessary to include in the design criteria. The experimental results demonstrate that, the proposed GLGSA remarkably improves the accuracy, stability and efficiency of the original algorithm.

Key Words
spread foundation; cost optimization; CO2 emissions optimization; gravitational search algorithm

Address
Mohammad Khajehzadeh : Department of Civil Engineering, Anar Branch, Islamic Azad University, Anar, Iran
Mohd Raihan Taha : Department of Civil and Structural Engineering, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia
Mahdiyeh Eslami : Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Kerman, Iran

Abstract
This paper reports the influence of number of layers and length of GFRP sheets wrapped onto RCC beams for strengthening. Twelve beams of size 700mm x 150mm x 150mm were cast and tested. Two beams without GFRP and ten beams wrapped in different lay-up patterns with one and two layers of GFRP sheets was subjected to three point loading test and ultrasonic pulse velocity test. Initial crack load, ultimate failure load and types of failure have been observed and noted. Experimental results indicate a significant increase in initial and ultimate load carrying capacity of GFRP wrapped beams compared to unwrapped beams. The failed control specimen was retrofitted using U wrap scheme and tested under three point loading.

Key Words
GFRP; wrapping schemes; strengthening; R C beam; flexure loading; retrofitting

Address
K.M. Mini, Rini John Alapatt, Anjana Elizabeth David, Aswathy Radhakrishnan, Minu Maria Cyriac and R. Ramakrishnan : Department of Civil Engineering, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Amrita Nagar, Coimbatore, Tamil Nadu, India

Abstract
A computer based iterative numerical procedure has been developed to analyse reinforced high strength concrete columns subjected to horizontal wave loads and eccentric vertical load by taking the material, geometrical and wave load non-linearity into account. The behaviour of the column has been assumed, to be represented by Moment-Thrust-Curvature relationship of the column cross-section. The formulated computer program predicts horizontal load versus deflection behaviour of a column up to failure. The developed numerical model has been applied to analyse several column specimens of various slenderness, structural properties and axial load ratios, tested by other researchers. The predicted values are having a better agreement with experimental results. A simplified user friendly hydrodynamic load model has been developed based on Morison equation supplemented with a wave slap term to predict the high frequency non-linear impulsive hydrodynamic loads arising from steep waves, known as ringing loads. A computer program has been formulated based on the model to obtain the wave loads and non-dimensional wave load coefficients for all discretised nodes, along the length of column from instantaneous free water surface to bottom of the column at mud level. The columns of same size and material properties but having different slenderness ratio are analysed by the developed numerical procedure for the simulated wave loads under various vertical thrust. This paper discusses the results obtained in detail and effect of slenderness in resisting wave loads under various vertical thrust.

Key Words
concrete column; wave loads; eccentric compression; Moment-Thrust-curvature; secondary moments

Address
M. Jayakumar : Department of Civil and Construction Engineering, Curtin University, Sarawak. Malaysia
B.V. Rangan : Faculty of Engineering and Computing, Curtin University, Perth, Australia

Abstract
Reliability-based design limit states and associated partial load factors provide a consistent level of design safety across bridge types and members. However, limit states in the current AASHTO LRFD have not been developed explicitly for the situation encountered by integral abutment bridges (IABs) that have unique boundary conditions and loads with inherent uncertainties. Therefore, new reliability-based limit states for IABs considering the variability of the abutment support conditions and thermal loading must be developed to achieve IAB designs that achieve the same safety level as other bridge designs. Prestressed concrete girder bridges are considered in this study and are subjected to concrete time-dependent effects (creep and shrinkage), backfill pressure, temperature fluctuation and temperature gradient. Based on the previously established database for bridge loads and resistances, reliability analyses are performed. The IAB limit states proposed herein are intended to supplement current AASHTO LRFD limit states as specified in AASHTO LRFD Table 3.4.1-1.

Key Words
structural reliability; bridge design; integral abutment;AASHTO, LRFD

Address
WooSeok Kim : Civil Engineering, Chungnam National University, Deajeon, 305-764, Korea
Jeffrey A. Laman : Civil and Environmental Engineering, Pennsylvania State University, University Park, PA, 16802, USA
Jong Yil Park : Safety Engineering, Seoul National University of Science and Technology, 139-743, Seoul, Korea

Abstract
This paper proposes a Particle Swarm Optimization (PSO) algorithm, which is improved by making use of the Harmony Search (HS) approach and called HS-PSO algorithm. A computer code is developed for optimal sizing design of non-linear steel frames with various semi-rigid and rigid beam-tocolumn connections based on the HS-PSO algorithm. The developed code selects suitable sections for beams and columns, from a standard set of steel sections such as American Institute of Steel Construction (AISC) wide-flange W-shapes, such that the minimum total cost, which comprises total member plus connection costs, is obtained. Stress and displacement constraints of AISC-LRFD code together with the size constraints are imposed on the frame in the optimal design procedure. The nonlinear moment-rotation behavior of connections is modeled using the Frye-Morris polynomial model. Moreover, the P-A effects of beam-column members are taken into account in the non-linear structural analysis. Three benchmark design examples with several types of connections are presented and the results are compared with those of standard PSO and of other researches as well. The comparison shows that the proposed HS-PSO algorithm performs better both than the PSO and the Big Bang-Big Crunch (BB-BC) methods.

Key Words
harmony search; Particle Swarm Optimization; semi-rigid connections; steel frames; optimal sizing design

Address
Ali Hadidi and Amin Rafiee : Department of Civil Engineering, University of Tabriz, Tabriz, Iran

Abstract
Perfectly matched layers are employed in time harmonic analysis of dam-foundation systems. The Lysmer boundary condition at the truncation boundary of the PML region has been incorporated in the formulation of the dam-foundation FE model (including PML). The PML medium is defined in a way that the formulation of the system can be transformed into time domain. Numerical experiments show that applying Lysmer boundary conditions at the truncation boundary of the PML area reduces the computational cost and make the PML approach a more efficient technique for the analysis of dam-foundation systems.

Key Words
wave propagation; semi-infinite domain; perfectly matched layers; dam-foundation system

Address
Adib Khazaee and Vahid Lotfi : Department of Civil and Environmental Engineering, Amirkabir University of Technology, 424 Hafez Ave., Tehran, Iran

Abstract
In this article, the force method and Charged System Search (CSS) algorithm are used for the analysis and optimal design of truss structures. The CSS algorithm is employed as the optimization tool and the force method is utilized for analysis. In this paper in addition to member\'s cross sections, redundant forces, geometry and topology variables are considered as the optimization variables. Minimum complementary energy principle is used directly to analyze the structure. In the presented method, redundant forces are calculated by the CSS in order to minimize the energy function. Combination of the CSS and force method leads to an efficient algorithm in comparison to some of the optimization algorithms.

Key Words
optimization; charged system search; force method; minimum complementary energy; truss structures

Address
A. Kaveh and B. Ahmadi : Centre of Excellence for Fundamental Studies in Structural Engineering, Iran University of Science and Technology, Narmak, Tehran 16, Iran

Abstract
Over the past years, hybrid building systems, consisting of reinforced concrete frames in bottom and steel frames in top are used as a cost-effective alternative to traditional structural steel or reinforced concrete constructions. Dynamic analysis of hybrid structures is usually a complex procedure due to various dynamic characteristics of each part, i.e. stiffness, mass and especially damping. In hybrid structures, one or more transitional stories with composite sections are used for better transition of lateral and gravity forces. The effect of transitional storey has been considered in no one of the studies in the field of hybrid structures damping. In this study, a method has been proposed to determining the equivalent modal damping ratios for hybrid steel-concrete buildings with transitional storey. In the proposed method, hybrid buildings are considered to have three structural systems, reinforced concrete, composite steel and concrete (transitional storey) and steel system. In this method, hybrid buildings are substituted appropriately with 3-DOF system.

Key Words
hybrid buildings; damping ratio; transitional storey; steel-concrete; non-classical damping; nonlinear analysis; main modes

Address
Abbas Sivandi-Pour, Mohsen Gerami and Daryush Khodayarnezhad : Faculty of Civil Engineering, Semnan University, Semnan, Iran

Abstract
The present paper addresses a general formulation for the thermo elastic analysis of a functionally graded cylindrical shell subjected to external loads. The shear deformation theory and energy method is employed for this purpose. This method presents the final relations by using a set of second order differential equations in terms of integral of material properties along the thickness direction. The proposed formulation can be considered for every distribution of material properties, whether functional or non functional. The obtained formulation can be used for manufactured materials or structures with numerical distribution of material properties which are obtained by using the experiments. The governing differential equation is applied for two well-known functionalities and some previous results are corrected with present true results.

Key Words
shear deformation theory; thermo elastic; shell; temperature; cylinder; energy

Address
M. Arefi : Department of Solid Mechanic, Faculty of Mechanical Engineering, University of Kashan, Kashan 87317-51167, Iran


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