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CONTENTS
Volume 9, Number 6, December 2009
 

Abstract
The present paper investigates the stochastic seismic responses of steel structure systems with Partially Restrained (PR) connections by using Perturbation based Stochastic Finite Element (PSFEM) method. A stiffness matrix formulation of steel systems with PR connections and PSFEM and MCS formulations of structural systems are given. Based on the formulations, a computer program in FORTRAN language has been developed, and stochastic seismic analyses of steel frame and bridge systems have been performed for different types of connections. The connection parameters, material and geometrical properties are assumed to be random variables in the analyses. The Kocaeli earthquake occurred in 1999 is considered as a ground motion. The connection parameters, material and geometrical properties are considered to be random variables. The efficiency and accuracy of the proposed SFEM algorithm are validated by comparison with results of Monte Carlo simulation (MCS) method.

Key Words
perturbation based stochastic finite element method; steel structures; PR connections; stiffness matrix; Monte Carlo simulation; stochastic dynamic analysis.

Address
Ozlem Cavdar; Gumushane University, Department of Civil Engineering, 29000, Gumushane, Turkey
Alemdar Bayraktar; Karadeniz Technical University, Department of Civil Engineering, 61080, Trabzon, Turkey
Ahmet Cavdar; Gumushane University, Department of Civil Engineering, 29000, Gumushane, Turkey
Murat Emre Kartal; Zonguldak Karaelmas University, Department of Civil Engineering, 67100, Zonguldak, Turkey

Abstract
This study intends to examine the characteristics of compressive behavior and conducts comparative analysis between normal compressive strength under existing equations (LRFD, ACI 318, EC 4) and experimental the maximum compressive strength from the compression experiment for the unstiffened steel plate-concrete structures. The six specimens were made to evaluate the constraining factor (x) and width ratio (b) effects subjected to the compressive monotonic loading. Based on this experiments, the following conclusions could be made: first, compressive behaviors of the specimens from the finite element analysis closely agreed with the ones from the actual experiments; second, the higher the width ratio (b) was, the lower the ductility index (DI) was; and third, the test results showed the maximum compressive strength with a margin by 7% compared to the existing codes.

Key Words
composite column(s); steel plate-concrete; initial stiffness; ductility index; ultimate strength; finite element analysis.

Address
Choi, Byong Jeong and Han, Hong Soo; Department of Architectural Engineering, Kyonggi University, Seoul, Korea

Abstract
The harmony search method based optimum design algorithm is presented for geometrically non-linear semi-rigid steel frames. Harmony search method is recently developed metaheuristic algorithm which simulates the process of producing a musical performance. The optimum design algorithm aims at obtaining minimum weight steel frames by selecting from standard set of steel sections such as European wide flange beams (HE sections). Strength constraints of Turkish Building Code for Steel Structures (TS648) specification and displacement constraints were used in the optimum design formulation. The optimum design algorithm takes into account both the geometric non-linearity of the frame members and the semi-rigid behaviour of the beam-to-column connections. The Frye-Morris polynomial model is used to calculate the moment- rotation relation of beam-to-column connections. The robustness of harmony search algorithm, in comparison with genetic algorithms, is verified with two benchmark examples. The comparisons revealed that the harmony search algorithm yielded not only minimum weight steel frames but also required less computational effort for the presented examples.

Key Words
optimum design; harmony search; steel frames; semi-rigid connections.

Address
S.O. Degertekin, M.S. Hayalioglu and H. Gorgun; Department of Civil Engineering, Dicle University, 21280, Diyarbakir, Turkey

Abstract
Fatigue tests for extremely thick plates require a great deal of manufacturing time and are expensive to perform. Therefore, if predictions could be made through simulation models such as an artificial neural network (ANN), manufacturing time and costs could be greatly reduced. In order to verify the effects of fatigue strength depending on the various factors in SM520C-TMC steels, this study constructed an ANN and conducted the learning process using the parameters of calculated stress concentration factor, thickness and input heat energy, etc. The results showed that the ANN could be applied to the prediction of fatigue life.

Key Words
prediction; fatigue life; fatigue strength; artificial neural network.

Address
Kim, Kyoung Nam; School of Civil Engineering, Chungbuk National University, Cheongju, Korea
Lee, Seong Haeng; Department of Civil Engineering, Pusan National University, Busan, Korea
Jung, Kyoung Sup; School of Civil Engineering, Chungbuk National University, Cheongju, Korea

Abstract
Corrosion of steel rebars in bridge decks which are faced to harsh conditions, is a common problem in construction industries due to the porosity of concrete. In this research, the behavior of one-way concrete slabs reinforced with Glass fiber reinforced polymer (GFRP) molded grating is investigated both theoretically and experimentally. In the analytical method, a closed-form solution for load-deflection behavior of a slab under four-point bending condition is developed by considering a concrete slab as an orthotropic plate and defining stiffness coefficients in principal directions. The available formulation for concrete reinforced with steel is expanded for concrete reinforced with GFRP molded grating to predict ultimate failure load. In finite element modeling, an exact nonlinear behavior of concrete along with a 3-D failure criterion for cracking and crushing are considered in order to estimate the ultimate failure load and the initial cracking load. Eight concrete slabs reinforced with steel and GFRP grating in various thicknesses are also tested to verify the results. The obtained results from the models and experiments are relatively satisfactory.

Key Words
concrete slab; molded grating; FEM; analytical solution; experiment.

Address
Shokrieh Mahmood Mehrdad and Heidari-Rarani Mohammad; Composites Research Laboratory, Department of Mechanical Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran 16844, Iran


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