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Volume 22, Number 3, October30 2016

This work presents a bending, buckling, and vibration analysis of functionally graded plates by employing a novel higher-order shear deformation theory (HSDT). This theory has only four unknowns, which is even less than the first shear deformation theory (FSDT). A shear correction coefficient is, thus, not needed. Unlike the conventional HSDT, the present one has a new displacement field which introduces undetermined integral variables. Equations of motion are obtained by utilizing the Hamilton's principles and solved via Navier's procedure. The convergence and the validation of the proposed theoretical numerical model are performed to demonstrate the efficacy of the model.

Key Words
bending; buckling; vibration; functionally graded plate; plate theory

(1) Habib Hebali:
Université Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algérie;
(2) Habib Hebali, Ahmed Bakora, Abdelouahed Tounsi, Abdelhakim Kaci:
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
(3) Abdelouahed Tounsi:
Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria;
(4) Abdelhakim Kaci:
Department of Civil Engineering and Hydraulics, University Dr. Taher Moulay of Saida, Algeria.

The confined concrete stress-strain curves utilised in computational models of concrete-filled steel tubular (CFST) columns can have a significant influence on the accuracy of the predicted behaviour. A generic model is proposed for predicting the stress-strain behaviour of confined concrete in short circular, elliptical and octagonal CFST columns subjected to axial compression. The finite element (FE) analysis is carried out to simulate the concrete confining pressure in short circular, elliptical and octagonal CFST columns. The concrete confining pressure relies on the geometric and material parameters of CFST columns. The post-peak behaviour of the concrete stressstrain curve is determined using independent existing experimental results. The strength reduction factor is derived for predicting the descending part of the confined concrete behaviour. The fibre element model is developed for the analysis of circular, elliptical and octagonal CFST short columns under axial loading. The FE model and fibre element model accounting for the proposed concrete confined model is verified by comparing the computed results with experimental results. The ultimate axial strengths and complete axial load-strain curves obtained from the FE model and fibre element model agree reasonably well with experimental results. Parametric studies have been carried out to examine the effects of important parameters on the compressive behaviour of short circular, elliptical and octagonal CFST columns. The design model proposed by Liang and Fragomeni (2009) for short circular, elliptical and octagonal CFST columns is validated by comparing the predicted results with experimental results.

Key Words
confined concrete model; numerical analysis; concrete-filled steel tubular columns

(1) Vipulkumar I. Patel:
School of Engineering and Mathematical Sciences, College of Science, Health and Engineering, La Trobe University, P.O. Box 199, Bendigo, VIC 3552, Australia;
(2) Brian Uy:
School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia;
(3) Prajwal K.A.:
Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India;
(4) Vipulkumar I. Patel, Brian Uy, Prajwal K.A., Farhad Aslani:
Centre for Infrastructure Engineering and Safety, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052, Australia;
(5) Farhad Aslani:
School of Civil, Environmental and Mining Engineering, The University of Western Australia, Crawley, WA 6009, Australia.

A Harmony Search (HS) and Genetic Algorithms (GA), two powerful metaheuristic search techniques, are used for minimum weight designs of different truss structures by selecting suitable profile sections from a specified list taken from American Institute of Steel Construction (AISC). A computer program is coded in MATLAB interacting with SAP2000-OAPI to obtain solution of design problems. The stress constraints according to AISC-ASD (Allowable Stress Design) and displacement constraints are considered for optimum designs. Three different truss structures such as bridge, dome and tower structures taken from literature are designed and the results are compared with the ones available in literature. The results obtained from the solutions for truss structures show that optimum designs by these techniques are very similar to the literature results and HS method usually provides more economical solutions in multi-element truss problems.

Key Words
AISC-ASD; harmony search algorithm; genetic algorithm; optimum design; truss structures

Department of Civil Engineering, Bayburt University, Bayburt 69000, Turkey.

Australian railway networks possess a large amount of aging timber components and need to replace them in excess of 280 thousands m3 per year. The relatively high turnover of timber sleepers (crossties in a plain track), bearers (skeleton ties in a turnout), and transoms (bridge cross beams) is responsible for producing greenhouse gas emissions 6 times greater than an equivalent reinforced concrete counterparts. This paper presents an innovative solution for the replacement of aging timber transoms installed on existing railway bridges along with the incorporation of a continuous walkway platform, which is proven to provide environmental, safety and financial benefits. Recent developments for alternative composite materials to replace timber components in railway infrastructure construction and maintenance demonstrate some compatibility issues with track stiffness as well as structural and geometrical track systems. Structural concrete are generally used for new railway bridges where the comparatively thicker and heavier fixed slab track systems can be accommodated. This study firstly demonstrates a novel and resilient alterative by incorporating steel-concrete composite slab theory and combines the capabilities of being precast and modulated, in order to reduce the depth, weight and required installation time relative to conventional concrete direct-fixation track slab systems. Clear benefits of the new steel-concrete composites are the maintainability and constructability, especially for existing railway bridges (or brown fields). Critical considerations in the design and finite element modelling for performance benchmarking of composite structures and their failure modes are highlighted in this paper, altogether with risks, compatibilities and compliances.

Key Words
railway infrastructure; resilient track slabs; modular components; precast composites; construction; maintenance; replacement; bridge

(1) Olivia Mirza, Kenny Kwok:
School of Computing, Engineering & Mathematics, University of Western Sydney, Kingswood, NSW 2747 Australia;
(2) Sakdirat Kaewunruen:
Birmingham Centre for Railway Research and Education, School of Engineering, The University of Birmingham, Edgbaston, B15 2TT, UK;
(3) Dane W.P. Griffin:
Rondo Consulting Pty Ltd., Penrith, NSW 2750 Australia.

The present investigation is to study the plane wave propagation and reflection of plane waves in a homogeneous transversely isotropic magnetothermoelastic medium with two temperature and rotation in the context of GN Type-II and Type-III (1993) theory of thermoelasticity. It is found that, for two dimensional assumed model, there exist three types of coupled longitudinal waves, namely quasi- longitudinal wave (QL), quasi- transverse wave (QTS) and quasi -thermal waves (QT). The different characteristics of waves like phase velocity, attenuation coefficients, specific loss and penetration depth are computed numerically and depicted graphically. The phenomenon of reflection coefficients due to quasi-waves at a plane stress free with thermally insulated boundary is investigated. The ratios of the linear algebraic equations. These amplitude ratios are used further to calculate the shares of different scattered waves in the energy of incident wave. The modulus of the amplitude and energy ratios with the angle of incidence are computed for a particular numerical model. The conservation of energy at the free surface is verified. The effect of energy dissipation and two temperatures on the energy ratios are depicted graphically and discussed. Some special cases of interest are also discussed.

Key Words
phase velocity; attenuation coefficients; specific loss; penetration depth; reflection; energy ratios

(1) Parveen Lata:
Department of Basic and Applied Sciences, Punjabi University, Patiala, Punjab, India;
(2) Rajneesh Kumar:
Department of Mathematics, Kurukshetra University, Kurukshetra, Haryana, India;
(3) Nidhi Sharma:
Department of Mathematics, MM University, Mullana, Ambala, Haryana, India.

The primary objectives of this research are to investigate the energy factor response of steel moment resisting frame (MRF) systems equipped with fuses subject to ground motions and to develop an energy-based evaluation approach for evaluating the damage-control behavior of the system. First, the energy factor of steel MRF systems with fuses below the resilience threshold is derived utilizing the energy balance equation considering bilinear oscillators with significant post-yielding stiffness ratio, and the effect of structural nonlinearity on the energy factor is investigated by conducting a parametric study covering a wide range of parameters. A practical transformation approach is also proposed to associate the energy factor of steel MRF systems with fuses with classic design spectra based on elasto-plastic systems. Then, the energy balance is extended to structural systems, and an energy-based procedure for damage-control evaluation is proposed and a damage-control index is also derived. The approach is then applied to two types of steel MRF systems with fuses to explore the applicability for quantifying the damagecontrol behavior. The rationality of the proposed approach and the accuracy for identifying the damage-control behavior are demonstrated by nonlinear static analyses and incremental dynamic analyses utilizing prototype structures.

Key Words
steel moment resisting frame system; structural fuse; damage-control; energy factor; singledegree-of-freedom system; evaluation approach

(1) Ke Ke:
State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China;
(2) Ke Ke:
College of Civil Engineering, Tongji University, Shanghai 200092, China;
(3) Michael C.H. Yam:
Department of Building and Real Estate, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.

The joints of the new prefabricated concrete assemble beam-column joints are put together by the hybrid joints of inserting steel under post-tensioned and non-prestressed force and both beams and columns adopt prefabricated components. The low cyclic loading test has been performed on seven test specimens of beam-column joints. Based on the experimental result, the rotation capacity of the joints is studied and the M-θ relation curve is obtained. According to Eurocode 3: Design of steel structures and based on the initial rotational stiffness, the joints are divided into three types; by equivalent bending-resistant stiffness to the precast beam, the equivalent modulus of elasticity Ee is elicited with the superposition method; the beam length is figured out that satisfies the rigid joints and after meeting the requirements of application and safety, the new prefabricated concrete assemble beam-column joints can be regarded as the rigid joints; the design formula adopted by the standard of concrete joint classification is theoretically derived ,thereby providing a theoretical basis for the new prefabricated concrete structure.

Key Words
beam-column joint; rotation capacity; stiffness of equivalent bending-resistant; standard of concrete joint classification

(1) Chun Han:
College of Civil Engineering and Architecture, Xinxiang University, Xinxiang, P.R. China;
(2) Qingning Li, Weishan Jiang:
College of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, P.R. China;
(3) Xin Wang:
United Architecture Design Group Shanghai, Incorporated, Wuhan 430000, P.R. China;
(4) Wei Li:
College of Civil Engineering and Architecture, Wenzhou University, Wenzhou, P.R. China.

When an eccentrically braced frame (EBF) is subjected to severe earthquakes, the links experience inelastic deformations while beams outside of the link, braces and columns are designed to remain elastic. To perform reliable inelastic analyses of EBFs sufficient analytical model which can accurately predict the inelastic performance of the links is needed. It is said in the literature that available analytical models for shear links generally predict very well the maximum shear forces and deformations from experiments on shear links, but may underestimate the intermediary values. In this study it is shown that available analytical models do not predict very well the maximum shear forces and deformations too. In this study an analytical model which can accurately predict both maximum and intermediary values of shear force and deformation is proposed. The model parameters are established based on test results from several experiments on shear links. Comparison of available test results with the hysteresis curves obtained using the proposed analytical model established the accuracy of the model. The proposed model is recommended to be used to perform inelastic analyses of EBFs.

Key Words
eccentrically braced frame; shear link; analytical model; inelastic analysis; hysteresis curves

(1) Amir Ashtari:
Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran;
(2) Saeed Erfani:
Department of Civil Engineering, Amirkabir University of Technology, Tehran, Iran.

This study aims to monitor the variation of modal frequencies of steel buildings during their construction sequence. In this respect, construction of a steel building is followed by vibration based measurements. The monitored building is a three-story educational building within a building group whose structural system consists of steel moment resisting steel frames and eccentric braces. Five different acceleration measurements in two perpendicular directions are taken on five different construction stages, starting from the erection of the columns and beams ending with the completion of the construction. The recorded measurements are transferred into frequency domain and the dominant frequencies for each case have been determined. The change in the dominant frequencies is evaluated with the existing construction stages and performed constructional works between the stages. The last measurement, performed on the building in service, revealed the first two dominant frequencies as mutual in X and Y direction, showing that these dynamic modes are torsional modes. This result is investigated by numerical analysis performed with finite element model of the building constructed for design purpose. Lower frequencies and different mode shapes are determined from numerical analysis. The reason of lower frequencies is discussed and the vibration survey is extended to determine the effects of an adjacent building. The results showed that the building is in strong relation with an adjoining building in spite of a designed construction joint.

Key Words
steel buildings; vibration survey; numerical modeling; dynamic analysis

Civil Engineering Department, Istanbul Medeniyet University, C Blok, No: 102, 34730, Uskudar, Istanbul, Turkey.

The effects of slenderness ratio, eccentricity and column slope on the load-carrying capacities and failure modes of variable and uniform concrete filled steel tubular (CFST) latticed columns under axial and eccentric compression were investigated and compared in this study. The results clearly show that all the CFST latticed columns with variable cross section exhibit an overall failure, which is similar to that of CFST latticed columns with a uniform cross section. The load-carrying capacity decreases with the increase of the slenderness ratio or the eccentricity. For 2-m specimens with a slenderness ratio of 9, the ultimate load-carrying capacity is increased by 3% and 5% for variable CFST latticed columns with a slope of 1:40 and 1:20 as compared with that of uniform CFST latticed columns, respectively. For the eccentrically compressed variable CFST latticed columns, the strain of the columns at the loading side, as well as the difference in the strain, increases from the bottom to the cap, and a more significant increase in strain is observed in the cross section closer to the column cap.

Key Words
concrete filled steel tubular latticed columns; axial compression; eccentric compression; stress mechanism; failure mode; load-carrying capacity

(1) Yan Yang, Jun Zhou, Jiangang Wei, Qingxiong Wu, Baochun Chen:
College of Civil Engineering, Fuzhou University, Fuzhou 350116, China;
(2) Lei Huang:
College of Civil Engineering and Architecture, Wuyi University, Nanping 354300, China.

In this paper, the effect of damping ratio on nonlinear dynamic analysis response and dynamic increase factor (DIF) in nonlinear static analysis of structures against column removal are investigated and a modified empirical DIF is presented. To this end, series of low and mid-rise moment frame structures with different span lengths and number of storeys are designed and the effect of damping ratio in DIF is investigated, performing several nonlinear static and dynamic analyses. For each damping ratio, a nonlinear dynamic analysis and a step by step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived. The results of the analysis reveal that DIF is decreased with increasing damping ratio. Finally, an empirical formula is recommended that relates to damping ratio. Therefore, the new modified DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of moment frame buildings with different damping ratios.

Key Words
progressive collapse; alternate load path; nonlinear static analysis; dynamic increase factor; damping ratio

Department of Civil Engineering, Shahid Bahonar University of Kerman, 22 Bahman Blvd. P.O. Box 76175-133, Kerman, Iran.

In this editorial, buckling analytical investigation of the nanocomposite plate with square cut out reinforced by carbon nanotubes (CNTs) surrounded by Pasternak foundation is considered. The plate is presumed has square cut out in center and resting on Pasternak foundation. CNTs are used as amplifier in plate for diverse distribution, such as uniform distribution (UD) and three patterns of functionally graded (FG) distribution types of CNTs (FG-X, FG-A and FG-O). Moreover, the effective mechanical properties of nanocomposite plate are calculated from the rule of mixture. Domain decomposition method and orthogonal polynomials are applied in order to define the shape function of nanocomposite plate with square cut out. Finally, Rayleigh-Ritz energy method is used to obtain critical buckling load of system. A detailed parametric study is conducted to explicit the effects of the dimensions of plate, length of square cut out, different distribution of CNTs, elastic medium and volume fraction of CNTs. It is found from results that increase the dimensions of plate and length of square cut out have negative impact on buckling behavior of system but considering CNTs in plate has positive influence.

Key Words
buckling analysis; nanocomposite plate; square cut out; domain decomposition method; orthogonal polynomials; Rayleigh-Ritz energy method

(1) M. Jamali, T. Shojaee, B. Mohammadi:
School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran;
(2) R. Kolahchi:
Faculty of Mechanical Engineering University of Kashan, Kashan, Iran.

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