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Volume 22, Number 2, October10 2016

In order to investigate mechanical properties and load-bearing capacity of T-shaped Concrete-Filled Square Steel Tubular (TCFST) composite columns under eccentric axial load, three T-shaped composite columns were tested under eccentric compression. Experimental results show that failure mode of the columns under eccentric compression was bending buckling of the whole specimen, and mono column performs flexural buckling. Specimens behaved good ductility and load-bearing capacity. Nonlinear finite element analysis was also employed in this investigation. The failure mode, the load-displacement curve and the ultimate bearing capacity of the finite element analysis are in good agreement with the experimental ones. Based on eccentric compression test and parametric finite element analysis, the calculation formula for the equivalent slenderness ratio was proposed and the bearing capacity of TCFST composite columns under eccentric compression was calculated. Results of theoretical calculation, parametric finite element analysis and eccentric compression experiment accord well with each other, which indicates that the theoretical calculation method of the bearing capacity is advisable.

Key Words
TCFST; finite element analysis; bearing capacity; the equivalent slenderness ratio; eccentric compression test

(1) Bin Rong:
Department of Civil Engineering, Tianjin University, Tianjin, 300072, China;
(2) Bin Rong, Guangchao You, Ruoyu Zhang, Changxi Feng, Rui Liu:
Key Laboratory of Coast Civil Structure Safety, Tianjin University, Tianjin, 300072, China.

This paper experimentally investigated the behavior of steel frame structures of traditional-style buildings subjected to combined constant axial load and reversed lateral cyclic loading conditions. The low cyclic reversed loading test was carried out on a 1/2 model of a traditional-style steel frame. The failure process and failure mode of the structure were observed. The mechanical behaviors of the steel frame, including hysteretic behaviors, order of plastic hinges, load-displacement curve, characteristic loads and corresponding displacements, ductility, energy dissipation capacity, and stiffness degradation were analyzed. Test results showed that the Dou-Gong component (a special construct in traditional-style buildings) in steel frame structures acted as the first seismic line under the action of horizontal loads, the plastic hinges at the beam end developed sufficiently and satisfied the Chinese Seismic Design Principle of "strong columns-weak beams, strong joints-weak members". The pinching phenomenon of hysteretic loops occurred and it changed into Z-shape, indicating shear-slip property. The stiffness degradation of the structure was significant at the early stage of the loading. When failure, the ultimate elastic-plastic interlayer displacement angle was 1/20, which indicated high collapse resistance capacity of the steel frame. Furthermore, the finite element analysis was conducted to simulate the behavior of traditional-style frame structure. Test results agreed well with the results of the finite element analysis.

Key Words
traditional-style buildings; steel frame structure; quasi-static test; mechanical behavior; finite element analysis

School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, P.R. China.

In this paper, a new simple higher-order shear deformation theory for bending and free vibration analysis of functionally graded (FG) plates is developed. The significant feature of this formulation is that, in addition to including a sinusoidal variation of transverse shear strains through the thickness of the plate, it deals with only three unknowns as the classical plate theory (CPT), instead of five as in the well-known first shear deformation theory (FSDT) and higher-order shear deformation theory (HSDT). A shear correction factor is, therefore, not required. Equations of motion are derived from Hamilton's principle. Analytical solutions for the bending and free vibration analysis are obtained for simply supported plates. The accuracy of the present solutions is verified by comparing the obtained results with those predicted by classical theory, first-order shear deformation theory, and higher-order shear deformation theory. Verification studies show that the proposed theory is not only accurate and simple in solving the bending and free vibration behaviours of FG plates, but also comparable with the other higher-order shear deformation theories which contain more number of unknowns.

Key Words
a simple 3-unknown theory; bending; vibration; functionally graded plates

(1) Mohammed Sid Ahmed Houari, Aicha Bessaim:
Université Mustapha Stambouli de Mascara, Department of Civil Engineering, Mascara, Algeria;
(2) Mohammed Sid Ahmed Houari, Abdelouahed Tounsi, Aicha Bessaim:
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) S.R. Mahmoud:
Department of Mathematics, Faculty of Science, King Abdulaziz University, Saudi Arabia;
(5) S.R. Mahmoud:
Mathematics Department, Faculty of Science, University of Sohag, Egypt.

In this paper, free vibration, forced vibration, resonance and stress wave propagation behavior in nanocomposite plates reinforced by wavy carbon nanotube (CNT) are studied by a mesh-free method based on first order shear deformation theory (FSDT). The plates are resting on Winkler-Pasternak elastic foundation and subjected to periodic or impact loading. The distributions of CNTs are considered functionally graded (FG) or uniform along the thickness and their mechanical properties are estimated by an extended rule of mixture. In the mesh-free analysis, moving least squares (MLS) shape functions are used for approximation of displacement field in the weak form of motion equation and the transformation method is used for imposition of essential boundary conditions. Effects of CNT distribution, volume fraction, aspect ratio and waviness, and also effects of elastic foundation coefficients, plate thickness and time depended loading are examined on the vibrational and stresses wave propagation responses of the nanocomposite plates reinforced by wavy CNT.

Key Words
stress wave; resonance; vibration; nanocomposite plates; wavy carbon nanotube; mesh-free

(1) Rasool Moradi-Dastjerdi:
Young Researchers and Elite Club, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr, Iran;
(2) Hamed Momeni-Khabisi:
Department of Mechanical Engineering, University of Jiroft, Jiroft, Iran.

The objective of this paper is to investigate buckling behavior of composite laminated cylinders by using semi-analytical finite strip method. The shell is subjected to deformation-dependent loads which remain normal to the shell middle surface throughout the deformation process. The load stiffness matrix, which is responsible for variation of load direction, is also throughout the deformation process. The shell is divided into several closed strips with alignment of their nodal lines in the circumferential direction. The governing equations are derived based on the first-order shear deformation theory with Sanders-type of kinematic nonlinearity. Displacements and rotations of the shell middle surface are approximated by combining polynomial functions in the meridional direction and truncated Fourier series along with an appropriate number of harmonic terms in the circumferential direction. The load stiffness matrix, which is responsible for variation of load direction, is also derived for each strip and after assembling, global load stiffness matrix of the shell is formed. The numerical illustrations concern the pressure stiffness effect on buckling pressure under various conditions. The results indicate that considering pressure stiffness causes buckling pressure reduction which in turn depends on various parameters such as geometry and lay-ups of the shell.

Key Words
deformation-dependent loads; finite strip method; buckling behavior; laminated composite; cylindrical shells

(1) Majid Khayat, Davood Poorveis:
Department of Civil Engineering, Shahid Chamran University of Ahvaz, Iran;
(2) Shapour Moradi:
Department of Mechanical Engineering, Shahid Chamran University of Ahvaz, Iran.

The results of a series of finite element (FE) simulations and experimental studies are used to develop strength and stiffness models that predict the failure capacity and response characteristics of unstiffened extended endplate connections with circular and rectangular bolt configurations associated with deep girders. The proposed stiffness models are composed of multi-linear springs which model the overall extended endplate/column flange system deformation and strength of key-components. Comparison of model predictions with FE and experimental results available in the literature show that the proposed models accurately predict the strength and the response of extended endplate/column system with circular and rectangular bolt configurations. The effect of the bolt configuration (circular and rectangular) on the prying phenomenon encountered in the unstiffened extended endplate/column system was investigated. Based on FE results, extended endplate with circular bolt configuration has a more ductile behavior and exhibits higher total prying forces. The proposed models can be used to design connections that cover all possible failure modes for extended endplate with circular bolt configuration. This study provides guidelines for engineers to account for the additional forces induced in the tension bolts and for the maximum rotational capacity demand in the connection which are required for seismic analysis and design.

Key Words
extended endplate; failure modes; circular bolts; finite element; strength and stiffness models; ductility

Department of Civil and Environmental Engineering, Faculty of Engineering and Architecture, American University of Beirut (AUB), Beirut, Lebanon.

This paper extends our recent work on the fatigue behavior of stud shear connectors in steel and recycled tyre rubber-filled concrete (RRFC) composite beams. A series of 16 fatigue push-out tests were conducted using a hydraulic servo testing machine. Three different recycled tyre rubber contents of concrete, 0%, 5% and 10%, were adopted as main variable parameters. Stress amplitudes and the diameters of studs were also taken into consideration in the tests. The results show that the fatigue lives of studs in 5% and 10% RRFC were 1.6 and 2.0 times greater of those in normal concrete, respectively. At the same time, the ultimate residual slips' values of stud increased in RRFC to highlight its better ductility. The average ultimate residual slip value of the studs was found to be equal to a quarter of studs' diameter. It had also been proved that stress amplitude was inversely proportional to the fatigue life of studs. Moreover, the fatigue lives of studs with large diameter were slightly shorter than those of smaller ones and using larger ones had the risk of tearing off the base metal. Finally, the comparison between test results and three national codes was discussed.

Key Words
recycled tyre rubber-filled concrete; rubber content; push-out test; S-N curve; stress amplitude; fatigue lives; residual slip

(1) Qing-Hua Han, Yi-Hong Wang, Jie Xu, Ying Xing:
School of Civil Engineering, Tianjin University, Tianjin 300072, China;
(2) Qing-Hua Han, Jie Xu:
Key Laboratory of Coast Civil Structure and Safety of Ministry of Education, Tianjin University, Tianjin 300072, China.

In this work, the two-dimensional generalized magneto-thermoelastic problem of a fiber-reinforced anisotropic material is investigated under Green and Naghdi theory of type III. The solution will be obtained for a certain model when the half space subjected to ramp-type heating and traction free surface. Laplace and exponential Fourier transform techniques are used to obtain the analytical solutions in the transformed domain by the eigenvalue approach. The inverses of Fourier transforms are obtained analytically. The results have been verified numerically and are represented graphically. Comparisons are made with the results predicted by the presence and absence of reinforcement and magnetic field.

Key Words
analytical solution; magnetothermoelasticity; fiber-reinforced material; eigenvalue approach; Green and Naghdi theory

(1) Faris S. Alzahrani:
Department of Mathematics, Faculty of Science, King Abdulaziz University, P.O. Box. 80203, Jeddah 21589, Saudi Arabia;
(2) Ibrahim A. Abbas:
Department of Mathematics, Faculty of Science and Arts - Khulais, University Of Jeddah, Saudi Arabia;
(3) Faris S. Alzahrani, Ibrahim A. Abbas:
Nonlinear Analysis and Applied Mathematics Research Group (NAAM), Department of Mathematics, King Abdulaziz University, Jeddah, Saudi Arabia;
(4) Ibrahim A. Abbas:
Department of Mathematics, Faculty of Science, Sohag University, Sohag, Egypt.

In order to evaluate the effects of U shape ultra high performance concrete (UHPC) permanent form on the behaviors of Reinforced Concrete (RC) beam, a full scale RC composite beam is designed and tested with U shape UHPC permanent form and a reference RC beam with same parameters is tested simultaneously for comparison. The effects of the permanent form on the failure mode, cracking strength, ultimate capacity and deformation are studied. Test results shows that the contributions of the U shape UHPC permanent form to the flexural cracking behaviors of RC beam are significant. This study may provide a reference for the design of sustainable RC beam with high durable UHPC permanent form.

Key Words
composite beam; cracking strength; flexural capacity; permanent form; ultra high performance concrete

(1) Xiangguo Wu:
Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, Harbin Institute of Technology, Harbin, 150090, China;
(2) Yang Lin:
School of Civil Engineering, Harbin Institute of Technology, Harbin, 150090, China.

The fracture propagation mechanism and fractured rock mass failure mechanism were important research in geotechnical engineering field. Many failures and instability in geotechnical engineering were related on fractures propagation, coalescence and interaction in rock mass under the external force. Most of the current research were limited to two-dimensional for the brittleness and transparency of three-dimensional fracture materials couldn't meet the requirements of the experiment. New materials with good transparent and brittleness were developed by authors. The making method of multi fracture specimens were established and made molds that could be reused. The tension-compression ratio of the material reached above 1/6 in normal temperature. Uniaxial and biaxial loading tests of single and double fracture specimens were carried out. Four new fractures were not found in the experiment of two-dimensional fractures such as the fin shaped crack, wrapping wing crack and petal crack and anti-wing crack. The relationship between stress and strain of the specimens were studied. The specimens with the load had experienced four stages of deformation and the process of the fracture propagation was clearly seen in each stage. The expansion characteristics of the fractured specimens were more obvious than the previous research.

Key Words
rock with fractures; transparent and brittle material; prefabricating crack; 3D crack extending; failure law

Geotechnical and Structural Engineering Research Center, Shandong University, No. 17923, Jingshi Road, Jinan, 250061, P.R. China.

In this study, by using finite element non-linear static analysis and comparing it with experimental models, the buckling and post-buckling behavior of bracing gusset plates has been investigated. The effects of such parameters as dimension and thickness of the gusset plate and the influence of position of the bracing member on the behavior of gusset plate have been examined. The results of the analyses clearly suggest that capacity, buckling and post-buckling behaviors of gusset plates depend on the position of the bracing splice plate with respect to the free bending line as well as on the size and thickness of the gusset plate. Also, with respect to numerical analysis results, some practical graphs for the calculation of buckling capacity of gusset plate connections are presented. For steel structures, the proposed method is apparently more accurate than available code procedures.

Key Words
steel structures; gusset plate; bracing splice plate; buckling; post-buckling; free bending line

(1) Mohammad Ali Hadianfard:
Department of Civil and Environmental Engineering, Shiraz University of Technology, P.O. Box 71555-313 Shiraz, Iran;
(2) Ali Reza Khakzad:
Eram Higher Education Institute, Shiraz, Iran.

This paper presents a finite element (FE) model for predicting the behaviour of steel column-column connections under axial compression and tension. A robustness approach is utilised for the design of steel columncolumn connections. The FE models take into account for the effects of initial geometric imperfections, material nonlinearities and geometric nonlinearities. The accuracy of the FE models is examined by comparing the predicted results with independent experimental results. It is demonstrated that the FE models accurately predict the ultimate axial strengths and load-deflection curves for steel column-column connections. A parametric study is carried out to investigate the effects of slenderness ratio, contact surface imperfection, thickness of cover-plates, end-plate thickness and bolt position. The buckling strengths of steel column-column connections with contact surface imperfections are compared with design strengths obtained from Australian Standards AS4100 (1998) and Eurocode 3 (2005). It is found that the column connections with maximum allowable imperfections satisfy the design requirements. Furthermore, the steel column-column connections analysed in this paper can be dismantled and reused safely under typical service loads which are usually less than 40% of ultimate axial strengths. The results indicate that steel column-column connections can be demounted at 50% of the ultimate axial load which is greater than typical service load.

Key Words
steel columns; column-column connection; robustness design; demountability; finite element analysis

(1) Dongxu Li, Brian Uy, Farhad Aslani:
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) Vipul Patel:
School of Engineering and Mathematical Sciences, College of Science, Health and Engineering, La Trobe University, PO Box 199, Bendigo, VIC 3552, Australia;
(4) Farhad Aslani:
School of Civil, Environmental and Mining Engineering, The University of Western Australia, Crawley, WA 6009, Australia.

This paper studies the seismic behavior of reinforced concrete (RC) walls with encased cold-formed and thin-walled (CFTW) steel truss, which can be used as an alternative to the conventional RC walls or steel reinforced concrete (SRC) composite walls for high-rise buildings in high seismic regions. Seven one-fourth scaled RC wall specimens with encased CFTW steel truss were designed, manufactured and tested to failure under reversed cyclic lateral load and constant axial load. The test parameters were the axial load ratio, configuration and volumetric steel ratio of encased web brace. The behaviors of the test specimens, including damage formation, failure mode, hysteretic curves, stiffness degradation, ductility and energy dissipation, were examined. Test results indicate that the encased web braces can effectively improve the ductility and energy dissipation capacity of RC walls. The steel angles are more suitable to be used as the web brace than the latticed batten plates in enhancing the ductility and energy dissipation. Higher axial load ratio is beneficial to lateral load capacity, but can result in reduced ductility and energy dissipation capacity. A volumetric ratio about 0.25% of encased web brace is believed cost-effective in ensuring satisfactory seismic performance of RC walls. The axial load ratio should not exceed the maximum level, about 0.20 for the nominal value or about 0.50 for the design value. Numerical analyses were performed to predict the backbone curves of the specimens and calculation formula from the Chinese Code for Design of Composite Structures was used to predict the maximum lateral load capacity. The comparison shows good agreement between the test and predicted results.

Key Words
wall; seismic performance; axial load ratio; brace; high-rise building

(1) Yun-tian Wu:
Key Laboratory of New Technology for Construction of Cities in Mountain Area, Ministry of Education, China;
(2) Yun-tian Wu, Dao-yang Kang, Yi-ting Su, Yeong-bin Yang:
School of Civil Engineering, Chongqing University, Chongqing 400045, China.

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