Techno Press
Tp_Editing System.E (TES.E)
Login Search


sem
 
CONTENTS
Volume 43, Number 6, September25 2012
 

Abstract
The goal of this study is to conceptually orientate optimized layouts of outrigger belt trusses which are in widespread use today in the design of tall buildings by strut-and-tie truss models utilizing a topology optimization method. In this study unknown strut-and-tie models are realized by using a typical SIMP method of topology optimization methods. In tradition strut-and-tie model designs find the appropriate strut-and-tie trusses along force paths with respect to elastic stress distribution, and then engineers or designers determine the most proper truss models by experience and intuition. It is linked to a trial-and-error procedure based on heuristic strategies. The presented strut-and tie model design by using SIMP provides that belt truss models are automatically and robustly produced by optimal layout information of struts-and-ties conforming to force paths without any trial-and-error. Numerical applications are studied to verify that outrigger belt trusses for tall buildings are optimally chosen by the proposed method for both static and dynamic responses.

Key Words
outrigger belt truss; topology optimization; tall buildings; strut-and-ties

Address
Dong-Kyu Lee: Architecture & Offshore Research Department, Steel Structure Research Division, Research Institute of Industrial Science & Technology, Korea
Jin-Ho Kim: Architecture & Offshore Research Department, Steel Structure Research Division, Research Institute of Industrial Science & Technology, Korea
Uwe Starossek: Structural Analysis and Steel Structures Institute, Hamburg University of Technology, Germany
Soo-Mi Shin: Research Institute of Industrial Technology, Pusan National University, Korea

Abstract
The temperature on steel structures is larger than the ambient air temperature under solar radiation and the temperature distribution on the affected structure is non-uniform and complicated. The steel tube, as a main structural member, has been investigated through experiment and numerical analysis. In this study, the temperature distribution on a properly designed steel tube under solar radiation is measured. A finite element transient thermal analysis method is presented and verified by the experimental results and a series of parametric studies are carried out to investigate the influence of various geometric properties and orientation on the temperature distribution. Furthermore, a simplified approach is proposed to predict the temperature distribution of steel tube. Based on both the experimental and the numerical results, it is concluded that the solar radiation has a significant effect on the temperature distribution of steel tubes. Under the solar radiation, the temperature of steel tubes is about 20.6oC higher than the ambient air temperature. The temperature distribution of steel tubes is sensitive to the steel solar radiation absorption, steel tube diameter and orientation, but insensitive to the solar radiation reflectance and thickness of steel tube.

Key Words
temperature; solar radiation; steel tube; numerical analysis; simplified calculation method

Address
Hongbo Liu: Department of Civil Engineering, Tianjin University, Tianjin, 300072, China
Zhihua Chen: Department of Civil Engineering, Tianjin University, Tianjin, 300072, China; Tianjin Key Laboratory of Civil Engineering Structure & New Materials, Tianjin University,
Tianjin, 300072, China
Ting Zhou: Department of Civil Engineering, Tianjin University, Tianjin, 300072, China

Abstract
The tailoring optimization technique recently developed by the author for improving structural response and energy absorption of composites is extended to sandwich shells using a previously developed zig-zag shell model with hierarchic representation of displacements. The in-plane variation of the stiffness properties of plies and the through-the thickness variation of the core properties are determined solving the Euler-Lagrange equations of an extremal problem in which the strain energy due to out-of-plane strains and stresses is minimised, while that due to their in-plane counterparts is maximised. In this way, the energy stored by unwanted out-of-plane modes involving weak properties is transferred to acceptable in-plane modes. As shown by the numerical applications, the critical interlaminar stress concentrations at the interfaces with the core are consistently reduced without any bending stiffness loss and the strength to debonding of faces from the core is improved. The structural model was recently developed by the author to accurately describe strain energy and interlaminar stresses from the constitutive equations. It a priori fulfills the displacement and stress contact conditions at the interfaces, considers a second order expansion of Lame

Key Words
tailoring optimisation; stress relaxation; strength improvement; sandwich shell; zig-zag model

Address
Ugo Icardi: Dipartimento di Ingegneria Meccanica e Aerospaziale, Politecnico di Torino - Corso Duca degli Abruzzi 24, 10129 Torino, Italy

Abstract
In this paper the Modified Finite Element-Transfer Matrix Method, which is the combination of Transfer Matrix Method and Finite Element Method, is applied to the static analysis of the structures. In the method, the structure is divided into substructures thus the number of unknowns that need to be worked out is reduced due to the transformation process. The static analysis of the structures can be performed easily and speedily by the proposed method. At the end of the study examples are presented for ensuring the agreement between the proposed method and classic Finite Element Method.

Key Words
modified finite element transfer matrix; transformation; static analysis

Address
D. Ozturk: Department of Civil Engineering, Engineering Faculty, Ege University, Izmir, Turkey
K. Bozdogan: Department of Civil Engineering, Engineering Faculty, Kirklareli University, Kirklareli, Turkey
A. Nuhoglu: Department of Civil Engineering, Engineering Faculty, Ege University, Izmir, Turkey

Abstract
This paper presents a multi-objective evolutionary algorithm for combinatorial optimisation and applied for design optimisation of fiber reinforced composite structures. The proposed algorithm closely follows the implementation of Pareto Archive Evolutionary strategy (PAES) proposed in the literature. The modifications suggested include a customized neighbourhood search algorithm in place of mutation operator to improve intensification mechanism and a cross over operator to improve diversification mechanism. Further, an external archive is maintained to collect the historical Pareto optimal solutions. The design constraints are handled in this paper by treating them as additional objectives. Numerical studies have been carried out by solving a hybrid fiber reinforced laminate composite cylindrical shell, stiffened composite cylindrical shell and pressure vessel with varied number of design objectives. The studies presented in this paper clearly indicate that well spread Pareto optimal solutions can be obtained employing the proposed algorithm.

Key Words
laminate composites; cylindrical shell; stiffened shell; multi-objective optimization; Pareto optimal solutions; neighbourhood search; evolutionary algorithm

Address
K. Lakshmi and A. Rama Mohan Rao: CSIR-Structural Engineering Research Centre, Taramani, Chennai, 600113, Tamil Nadu, India

Abstract
The size and topology of geometrically nonlinear dome structures are optimized thereby minimizing both its entire weight & joint (node) displacements and maximizing load-carrying capacity. Design constraints are implemented from provisions of American Petroleum Institute specification (API RP2A-LRFD). In accordance with the proposed design constraints, the member responses computed by use of arc-length technique as a nonlinear structural analysis method are checked at each load increment. Thus, a penalization process utilized for inclusion of unfeasible designations to genetic search is correspondingly neglected. In order to solve this complex design optimization problem with multiple objective functions, Non-dominated Sorting Genetic Algorithm II (NSGA II) approach is employed as a multi-objective optimization tool. Furthermore, the flexibility of proposed optimization is enhanced thereby integrating an automatic dome generating tool. Thus, it is possible to generate three distinct sphere-shaped dome configurations with varying topologies. It is demonstrated that the inclusion of brace (diagonal) members into the geometrical configuration of dome structure provides a weight-saving dome designation with higher load-carrying capacity. The proposed optimization approach is recommended for the design optimization of geometrically nonlinear dome structures.

Key Words
dome structure; geometrically nonlinear; NSGAII; API RP2A-LRFD

Address
Talaslioglu Tugrul: Department of Civil Engineering, Osmaniye Korkut Ata University, 8000, Osmaniye, Turkey

Abstract
An experimental method was suggested for obtaining fracture toughness (KIc) and the tensile strength (at) of chopped strand glass fiber reinforced polymer concretes (PC). Semi-circular bend (SCB) specimens subjected to three-point bending were used for conducting the experiments on the PC material. While the edge cracked SCB specimen could be used to evaluate fracture toughness, the tensile strength was obtained from the un-cracked SCB specimen. The experiments showed the practical applicability of both cracked and un-cracked SCB specimens for using as suitable techniques for measuring KIc and at in polymer concretes. In comparison with the conventional rectangular bend beam specimen, the suggested SCB samples need significantly less material due to its smaller size. Furthermore, the average values of

Key Words
polymer concrete; SCB specimen; tensile strength; fracture toughness; experiment

Address
M.R.M. Aliha: Fatigue and Fracture Laboratory, Center of Excellence in Experimental Solid Mechanics and Dynamics,
School of Mechanical Engineering, Iran University of Science and Technology (IUST), Tehran 16846-13114, Iran; Welding and Joining Research Center, School of Industrial Engineering, Iran University of Science and Technology (IUST),Tehran 16846-13114, Iran
M. Heidari-Rarani: Composites Research Laboratory, Center of Excellence in Experimental Solid Mechanics and Dynamics, School of Mechanical Engineering, Iran University of Science and Technology (IUST), Tehran 16846-13114, Iran
M.M. Shokrieh: Composites Research Laboratory, Center of Excellence in Experimental Solid Mechanics and Dynamics, School of Mechanical Engineering, Iran University of Science and Technology (IUST), Tehran 16846-13114, Iran
M.R. Ayatollahi: Fatigue and Fracture Laboratory, Center of Excellence in Experimental Solid Mechanics and Dynamics, School of Mechanical Engineering, Iran University of Science and Technology (IUST), Tehran 16846-13114, Iran

Abstract
This paper focuses on the stochastic response analysis of industrial masonry chimneys to surface blast-induced random ground motions by using a three dimensional finite element model. Underground blasts induce ground shocks on nearby structures. Depending on the distance between the explosion centre and the structure, masonry structures will be subjected to ground motions due to the surface explosions. Blast-induced random ground motions can be defined in terms of the power spectral density function and applied to each support point of the 3D finite element model of the industrial masonry system. In this paper, mainly a parametric study is conducted to estimate the effect of the blastinduced ground motions on the stochastic response of a chimney type masonry structure. With this purpose, different values of charge weight and distance from the charge centre are considered for the analyses of the chimney. The results of the study underline the remarkable effect of the surface blastinduced ground motions on the stochastic behaviour of industrial masonry type chimneys.

Key Words
industrial masonry chimney; blast-induced ground motion; stochastic dynamic analysis; power spectral density function; charge weight; charge centre

Address
Kemal Haciefendioglu: Department of Civil Engineering, Ondokuz May s University, 55139, Samsun, Turkey
Kurtulus Soyluk: Department of Civil Engineering, Gazi University, Maltepe, 06570 Ankara, Turkey


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com