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Volume 22, Number 4, November20 2016

A novel four variable refined plate theory is proposed in this work for laminated composite plates. The theory considers a parabolic distribution of the transverse shear strains, and respects the zero traction boundary conditions on the surfaces of the plate without employing shear correction coefficient. The displacement field is based on a novel kinematic in which the undetermined integral terms are used, and only four unknowns are involved. The analytical solutions of antisymmetric cross-ply and angle-ply laminates are determined via Navier technique. The obtained results from the present model are compared with three-dimensional elasticity solutions and results of the first-order and the other higher-order theories reported in the literature. It can be concluded that the developed theory is accurate and simple in investigating the bending and buckling responses of laminated composite plates.

Key Words
laminated composite plates; refined plate theory; navier solution

(1) Slimane Merdaci, Abdelouahed Tounsi, Ahmed Bakora:
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
(2) 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.

In this study, optimum structural designs of braced (non-swaying) planar steel frames are investigated by using one of the recent meta-heuristic search techniques, teaching.learning based optimization. Optimum design problems are performed according to American Institute of Steel Construction- Allowable Stress Design (AISCASD) specifications. A computer program is developed in MATLAB interacting with SAP2000 OAPI (Open Application Programming Interface) to conduct optimization procedures. Optimum cross sections are selected from a specified list of 128W profiles taken from AISC. Two different braced planar frames taken from literature are carried out for stress, geometric size, displacement and inter-storey drift constraints. It is concluded that teaching-learning based optimization presents robust and applicable optimum solutions in multi-element structural problems.

Key Words
teaching-learning based optimization; optimum design; planar steel frames; MATLABSAP2000 OAPI

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

An investigation has been done to study the evolution of the microstructure, mechanical and electrical properties of AlMgSi alloy destined for the transport of electric energy, in function of the deformation caused by the cold drawing process. We identified that drawing of aluminum wire causes development of a fibrous texture of type <111> and <100>. We notice also that the electrical resistivity and mechanical resistance increases with the increasing of the deformation level. Characterization methods used in this work is: The Electron Back Scattered Diffraction EBSD, X-Ray diffraction, Vickers microhardness, Tensile test, Measuring electrical resistivity, the Scanning Electron Microscope (SEM) and Energy Diffraction Spectrum (EDS).

Key Words
aluminum alloy; microstructure; texture; electrical resistivity; mechanical resistance; deformation by drawing wire

(1) M. Zidani, L. Bessais, M.D. Hadid, S. Messaoudi:
Laboratoire de Génie Energétique et Matériaux, Université de Biskra, Biskra, Algérie;
(2) H. Farh:
Laboratoire des composants actif et matériaux, Oum el Bouaghi, Algeria;
(3) D. Miroud:
Laboratoire des Sciences et Génie des Matériaux (LSGM), USTHB, Alger, 16000 Algérie;
(4) M.K. Loudjani, A.L. Helbert, T. Baudin:
ICMMO, SP2M, Univ Paris-Sud, Universite Paris-Saclay, UMR CNRS 8182, 91405, Orsay Cedex, France.

This paper aims to investigate the demountability of steel column-baseplate connections subjected to monotonic and cyclic loading. This paper presents the finite element analysis of steel column-baseplate connections under monotonic and cyclic loading. The finite element model takes into account the effects of material and geometric nonlinearities. Bauschinger and pinching effects were also included in the developed model, through which degradation of steel yield strength in cyclic loading can be well simulated. The results obtained from the finite element model are compared with the existing experimental results. It is demonstrated that the finite element model accurately predicts the initial stiffness, ultimate bending moment strength of steel column-baseplate connections. The finite element model is utilised to examine the effects of axial load, baseplate thickness, anchor bolt diameter and position on the behaviour of steel column-baseplate connections. The effects of various parameters on the demountability of steel column-baseplate connections are investigated. To achieve a demountable and reusable structure, various design parameters need to be considered. Initial stiffness and moment capacity of steel columnbaseplate connections are compared with design strengths from Eurocode 3. The comparison between finite element analysis and Eurocode 3 indicates that predictions of initial stiffness for semi-rigid connections should be developed and improved design of the connections needs to be used in engineering practice.

Key Words
steel columns; column-baseplate connections; monotonic and cyclic loading; demountability; finite element analysis

(1) Dongxu Li, Brian Uy:
Centre for Infrastructure Engineering and Safety, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052, Australia;
(2) Brian Uy:
School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia;
(3) Farhad Aslani:
School of Civil, Environmental and Mining Engineering, The University of Western Australia, Crawley, WA 6009, Australia;
(4) Vipul Patel:
School of Engineering and Mathematical Sciences, College of Science, Health and Engineering, La Trobe University, P.O. Box 199, Bendigo, VIC 3552, Australia.

In this paper, the behavior of woven E-glass fabric composite laminate was experimentally investigated under quasi-static indentation and high velocity impact by flat-ended, hemispherical, conical (cone angle of 37° and 90°) and ogival (CRH of 1.5 and 2.5) cylindrical perforators. Moreover, the results are compared in order to explore the possibility of extending quasi-static indentation test results to high velocity impact test results in different characteristics such as perforation mechanisms, performance of perforators, energy absorption, friction force, etc. The effects of perforator nose shape, nose length and nose-shank connection shapes were investigated. The results showed that the quasi-static indentation test has a great ability to predict the high velocity impact behavior of the composite laminates especially in several characteristics such as perforation mechanisms, perforator performance. In both experiments, the highest performance occurs for 2.5 CRH projectile and the lowest is related to blunt projectiles. The results show that sharp perforators indicate lower values of dynamic enhancement factor and the flat-ended perforator represents the maximum dynamic enhancement factor among other perforators. Moreover, damage propagation far more occurred in high velocity impact tests then quasi-static tests. The highest damage area is mostly observed in ballistic limit of each projectile which projectile deviation strongly increases this area.

Key Words
static perforation; dynamic perforation; projectile nose shape; woven fabric composite laminate; energy absorption

(1) E. Mehrabani Yeganeh, G.H. Liaghat:
Department of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran;
(2) M.H. Pol:
Department of Mechanical Engineering, Tafresh University, Tafresh, Iran.

This paper simulates the hysteretic behavior of steel reinforced recycled concrete (SRRC) columns under cyclic loads using OpenSees software. The effective fiber model and displacement-based beam-column element in OpenSees is applied to each SRRC columns. The Concrete01 material model for recycled aggregate concrete (RAC) and Steel02 material model is proposed to perform the numerical simulation of columns. The constitutive models of RAC, profile steel and rebars in columns were assigned to each fiber element. Based on the modelling method, the analytical models of SRRC columns are established. It shows that the calculated hysteresis loops of most SRRC columns agree well with the test curves. In addition, the parameter studies (i.e., strength grade of RAC, stirrups strength, steel strength and steel ratio) on seismic performance of SRRC columns were also investigated in detail by OpenSees. The calculation results of parameter analysis show that SRRC columns suffered from flexural failure has good seismic performance through the reasonable design. The ductility and bearing capacity of columns increases as the increasing magnitude of steel strength, steel ratio and stirrups strength. Although the bearing capacity of columns increases as the strength grade of RAC increases, the ductility and energy dissipation capacity decreases gradually. Based on the test and numerical results, the flexural failure mechanism of SRRC columns were analysed in detail. The computing theories of the normal section of bearing capacity for the eccentrically loaded columns were adopted to calculate the nominal bending strength of SRRC columns subjected to vertical axial force under lateral cyclic loads. The calculation formulas of horizontal bearing capacity for SRRC columns were proposed based on their nominal bending strength.

Key Words
steel reinforced recycled concrete (SRRC); columns; OpenSees software; numerical analysis; flexural failure; horizontal bearing capacity

(1) Hui Ma, Yunhe Liu, Jing Dong:
School of Civil Engineering and Architecture, Xi\'an University of Technology, Xi\'an, P.R. China;
(2) Jianyang Xue:
School of Civil Engineering, Xi\'an University of Architecture and Technology, Xi\'an, P.R. China.

The paper presents an experimental study of the structural behavior of circular flyash-concrete-filled steel tubular stub columns under axial compressive loads. In this study, 90% and 100% by weight of the cement in the concrete core was replaced with flyash. Twenty-seven specimens were tested to study the influence of flyash content, wall thickness of the steel tube, and curing age on the ultimate capacity and confinement effect. The experimental results were compared with the design values calculated using AISC-LRFD (1999), ACI (1999), AIJ (1997) and Eurocode 4 (1994). From the experimental study, it was determined that the confinement effect of circular steel tubes filled with high content flyash concrete was better than that of specimens filled with ordinary Portland cement concrete. The 5.88-mm-thick steel tube filled with 100% flyash concrete was equivalent in strength to a steel tube filled with C30 concrete at 28 days.

Key Words
flyash-concrete-filled steel tubes; stub columns; ultimate load-carrying capacity; confinement effect

(1) Yang Zhang, Guang-Yuan Fu, Chen-Jiang Yu, She-Xu Zhao, Si-Ping Li:
Department of Engineering Mechanics, Shanghai Jiao Tong University, Shanghai 200240, P.R. China;
(2) Yang Zhang:
School of Civil Engineering, Nanyang Institute of Technology, Nanyang 473004, P.R. China;
(3) Bing Chen:
Department of Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, P.R. China.

This paper presents the experimental and numerical study on the distribution of transverse and longitudinal residual stresses in cold-formed thick-walled structural steel rectangular hollow sections manufactured by indirect technique. Hole-drilling method is employed to measure the magnitude of the transverse and longitudinal surface residual stress distribution, and the effects of the residual stresses are evaluated qualitatively by sectioning method. It is shown that compared to normal cold-formed thin-walled structural hollow sections (SHS), the coldformed thick-walled SHS has similar level of residual stress in the flat area but higher residual stresses in the corner and welding areas. Both the transverse and longitudinal residual stresses tend to open the section. In order to predict the surface residual stresses in the corners of the cold-formed thick-walled SHS, an analytical model is developed. 2D finite element simulation of the cold bending process is conducted to validate the analytical approach. It is shown that in analyzing bending for thick-walled sections, shifting of neutral axis must be considered, since it would lead to nonlinear and non-symmetrical distribution of stresses through the thickness. This phenomenon leads to the fact that cold-formed thick-walled SHSs has different distribution and magnitude of the residual stresses from the cold-formed thin-walled SHSs.

Key Words
cold-formed; thick-walled; structural hollow section; residual stress; analytical model

(1) Xingzhao Zhang, Su Liu:
School of Architecture, Hunan University, P.R. China;
(2) Mingshan Zhao:
School of Civil and Environmental Engineering, Nanyang Technological University, Singapore;
(3) Sing-Ping Chiew:
Singapore Institute of Technology, Singapore.

In this paper, it is aimed to evaluate the earthquake angle influence on the seismic performance of steel highway bridges. Upper-deck steel highway bridge, which has arch type load bearing system with a total length of 216 m, has been selected as an application and analyzed using finite element methods. The bridge is subjected to 1992 Erzincan earthquake ground motion components in nineteen directions whose values range between 0 to 90 degrees, with an increment of 5 degrees. The seismic weight is calculated using full dead load plus 30% of live load. The variation of maximum displacements in each directions and internal forces such as axial forces, shear forces and bending moments for bridge arch and deck are attained to determine the earthquake angle influence on the seismic performance. The results show that angle of seismic input motion considerably influences the response of the bridge. It is seen that maximum arch displacements are obtained at X, Y and Z direction for 0°, 65° and 5°, respectively. The results are changed considerably with the different earthquake angle. The maximum differences are calculated as 57.06%, 114.4% and 55.71% for X, Y and Z directions, respectively. The maximum axial forces, shear forces and bending moments are obtained for bridge arch at 90°, 5° and 0°, respectively. The maximum differences are calculated as 49.12%, 37.37% and 51.50%, respectively. The maximum shear forces and bending moments are obtained for bridge deck at 0°. The maximum differences are calculated as 49.67%, and 49.15%, respectively. It is seen from the study that the variation of earthquake angle effect the structural performance of highway bridges considerably. But, there is not any specific earthquake angle of incidence for each structures or members which increases the value of internal forces of all structural members together. Each member gets its maximum value of in a specific angle of incidence.

Key Words
earthquake angle effect; finite element method; seismic performance; steel bridge

Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkey.

The proper selection of materials for the intended use of the structural member is of particular interest. The paper deals with determining both the mechanical properties at different temperatures and the behavior in tensile creep as well as fatigue testing of tensile stressed specimens made of low alloy 42CrMo4 steel delivered as annealed and cold drawn. This steel is usually used in engineering practice in design of statically and dynamically stressed components. Displayed engineering stress - strain diagrams indicate the mechanical properties, creep curves indicate the material creep behavior while experimental investigations of fatigue may ensure the fatigue limit determination for considered stress ratio. Also, hardness testing provides an insight into material resistance to plastic deformation. Experimentally obtained results regarding material properties were: tensile strength (735 MPa / 20°C, 105 MPa / 680°C), yield strength (593 MPa / 20°C, 76 MPa /680°C). Fatigue limit in the amount of 532.26 MPa, as maximum stress at stress ratio R = 0.25 at ambient temperature was calculated on the basis of experimentally obtained results. Regarding the creep resistance it is visible that this steel can be treated as creep resistant at high temperatures (including 580°C) when applied stress is of low level (till 0.2 of yield stress).

Key Words
42CrMo4 steel; mechanical properties; short-time creep; fatigue; fatigue limit

(1) Josip Brnic, Marko Canadija, Goran Turkalj, Sanjin Krscanski, Domagoj Lanc, Marino Brcic:
Faculty of Engineering, University of Rijeka, Vukovarska 58, 51000 Rijeka, Croatia;
(2) Zeng Gao:
School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo, China.

Vibration analysis of embedded functionally graded (FG)-carbon nanotubes (CNT)-reinforced piezoelectric cylindrical shell subjected to uniform and non-uniform temperature distributions are presented. The structure is subjected to an applied voltage in thickness direction which operates in control of vibration behavior of system. The CNT reinforcement is either uniformly distributed or functionally graded (FG) along the thickness direction indicated with FGV, FGO and FGX. Effective properties of nano-composite structure are estimated through Mixture low. The surrounding elastic foundation is simulated with spring and shear constants. The material properties of shell and elastic medium constants are assumed temperature-dependent. The motion equations are derived using Hamilton's principle applying first order shear deformation theory (FSDT). Based on differential cubature (DC) method, the frequency of nano-composite structure is obtained for different boundary conditions. A detailed parametric study is conducted to elucidate the influences of external applied voltage, elastic medium type, temperature distribution type, boundary conditions, volume percent and distribution type of CNT are shown on the frequency of system. In addition, the mode shapes of shell for the first and second modes are presented for different boundary conditions. Numerical results indicate that applying negative voltage yields to higher frequency. In addition, FGX distribution of CNT is better than other considered cases.

Key Words
vibration of piezoelectric shell; FG-CNT; DC method; Non-uniform temperature distribution; temperature-dependent

(1) Hamid Madani:
Young Researcher and Elite Club, Jasb Branch, Islamic Azad University, Jasb, Iran;
(2) Hadi Hosseini:
Department of Civil Engineering, Khomein Branch, Islamic Azad University, Khomein, Iran;
(3) Maryam Shokravi:
Buein Zahra Technical University, Buein Zahra, Qazvin, Iran.

Steel systems composed of Reinforced Concrete column to Steel beam connection (RCS) have been raised as a structural system in the past few years. The optimized combination of steel-concrete structural elements has the advantages of both systems. Through beam and through column connections are two main categories in RCS systems. This study includes finite-element analyses of mentioned connection to investigate the seismic performance of RCS connections. The finite element model using ABAQUS software has been verified with experimental results of a through beam type connection tested in Taiwan in 2005. According to verified finite element model a parametric study has been carried out on five RCS frames with different types of lateral restraint system. The main objective of this study is to investigate the forming of plastic hinges, distribution of stresses, ductility and stiffness of these models. The results of current research showed good performance of composite systems including concrete column-steel beam in combination with steel shear wall and bracing system, are very desirable. The results show that the linear stiffness of models with X bracing and steel shear wall increase remarkably and their ultimate strength increase about three times rather than other RCS frames.

Key Words
concrete column; steel beam; connection; finite element; RCS; shear wall; bracing

(1) Saeedeh Ghods, Ali Kheyroddin, Majid Gholhaki:
Depatment of Civil Engineering, Semnan University, Semnan, Iran;
(2) Meissam Nazeryan:
Depatment of Civil engineering, Sharif University of Technology, Tehran, Iran;
(3) Seyed Masoud Mirtaheri:
Department of Civil Engineering, K.N. Toosi University of Technology, Tehran, Iran.

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