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CONTENTS
Volume 1, Number 4, October 2016
 

Abstract
The flexural strength of circular concrete-filled tubes (CCFT) can be estimated by several codes such as ACI, AISC, and Eurocode 4. In AISC and Eurocode, two methods are recommended, which are the strain compatibility method (SCM) and the plastic stress distribution method (PSDM). The SCM of AISC is almost the same as the SCM of the ACI method, while the SCM of Eurocode is similar to the ACI method. Only the assumption of the compressive stress of concrete is different. The PSDM of Eurocode approach is also similar to the PSDM of AISC, but they have different definitions of material strength. The PSDM of AISC is relatively easier to use, because AISC provides closed-form equations for calculating the flexural strength. However, due to the complexity of calculation of circular shapes, it is quite difficult to determine the flexural strength of CCFT following other methods. Furthermore, all these methods give different estimations. In this study, an effort is made to review and compare the codes to identify their differences. The study also develops a computing program for the flexural strength of circular concrete filled tubes under pure bending that is in accordance with the codes. Finally, the developed computing algorithm, which is programmed in MATLAB, is used to generate design aid graphs for various steel grades and a variety of strengths of steel and concrete. These design aid graphs for CCFT beams can be used as a preliminary design tool.

Key Words
flexural strength; circular concrete-filled tube; computing algorithm; design aid graph

Address
Minsun Lee and Thomas H.-K. Kang: Department of Architecture and Architectural Engineering, Seoul National University,1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea

Thomas H.-K. Kang: Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign,
205 North Mathews Ave., Urbana 61810, USA

Abstract
Damage detection and localisation in structures is essential since it can be a means for preventive maintenance of those structures under service conditions. The use of structural modal data for detecting the damage is one of the most efficient methods. This paper presents comparative performance of various stateof-the-art meta-heuristics for use in structural damage detection based on changes in modal data. The metaheuristics include differential evolution (DE), artificial bee colony algorithm (ABC), real-code ant colony optimisation (ACOR), charged system search (ChSS), league championship algorithm (LCA), simulated annealing (SA), particle swarm optimisation (PSO), evolution strategies (ES), teaching-learning-based optimisation (TLBO), adaptive differential evolution (JADE), evolution strategy with covariance matrix adaptation (CMAES), success-history based adaptive differential evolution (SHADE) and SHADE with linear population size reduction (L-SHADE). Three truss structures are used to pose several test problems for structural damage detection. The meta-heuristics are then used to solve the test problems treated as optimisation problems. Comparative performance is carried out where the statistically best algorithms are identified.

Key Words
structural health monitoring; meta-heuristics; modal data; damage detection

Address
Nantiwat Pholdee and Sujin Bureerat: Sustainable and Infrastructure Research and Development Center, Department of Mechanical Engineering, Faculty of Engineering, Khon Kaen University, Thailand

Abstract
In this paper, a methodology to simulate the whole-building behaviour of the tall building under fire is developed by the author using a 3-D nonlinear finite element method. The mechanical and thermal material nonlinearities of the structural members, such as the structural steel members, concrete slabs and reinforcing bars were included in the model. In order to closely simulate the real condition under the conventional fire incident, in the simulation, the fire temperature was applied on level 9, 10 and 11. Then, a numerical investigation on the whole-building response of the building in fire was made. The temperature distribution of the floor slabs, steel beams and columns were predicted. In addition, the behaviours of the structural members under fire such as beam force, column force and deflections were also investigated.

Key Words
tall building; fire; whole-building response; composite; steel; thermal behaviour

Address
School of Mathematics, Computer Science & Engineering, Department of Civil Engineering, City University of London, UK

Abstract
Notwithstanding a considerable body of references in the literature on the buckling response of conical shell structures, it seems imperative to provide further insight on the buckling response of locally imperfect steel cones. This paper contains different simulations including non-linear FE analysis and discusses the influence of dent imperfection on the buckling load of these structures subject to external pressure. Data of the present work are evaluated against available experimental results, codes and recommendations and the effect of the local damages is exhaustively set forth. It is also found that the employed FE program can reliably predict the structural response of locally damaged conical shells.

Key Words
conical shells; dent imperfection; external pressure; FE analysis

Address
Tohid Ghanbari Ghazijahani, Hui Jiao: School of Engineering and ICT, University of Tasmania, Sandy Bay Campus, Hobart, TAS 7001, Australia

Hossein Showkati: Department of Civil Engineering, Urmia University, Iran

Abstract
This paper aims to examine the dynamic response of a newly designed ultrasonic motor under half-sine shock impulses. Impact shock was applied to the motor along x, y or z axis respectively with different pulse widths to check the sensitivity of the motor to the shocks in different directions. Finite Element Analysis (FEA) with the ANSYS software was conducted to obtain the relative displacement of a key point of the motor. Numerical results show that the maximum relative displacement is of micro meter level and the maximum stress is five orders smaller than the Young´s modulus of the piezo material, which proves the robustness of the motor.

Key Words
standing wave ultrasonic motor; shock analysis; finite element method; piezoelectric stack

Address
Xiaoyan Hou, Heow Pueh Lee, Chong Jin Ong and Siak Piang Lim: Department of Mechanical Engineering, National University of Singapore, 21 Lower Kent Ridge Road, Singapore


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