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CONTENTS
Volume 28, Number 4, August25 2018
 

Abstract
In this paper, the lateral-torsional buckling of axially-transversally functionally graded tapered beam is investigated. The structure cross-section is assumed to be symmetric I-section, and it is continuously laterally supported by torsional springs through the length. In addition, the height of cross-section varies linearly throughout the length of structure. The proposed formulation is obtained for the case that the elastic and shear modulus change as a power function along the beam length and section height. This structure carries two concentrated moments at the ends. In this study, the lateral displacement and twisting angle relation of the beam are defined by sinusoidal series. After establishing the eigenvalue equation of unknown constants, the beam critical bending moment is found. To validate the accuracy and correctness of results, several numerical examples are solved.

Key Words
functionally graded material; lateral and torsional buckling; tapered beam; warping; continuous torsional bracing

Address
Department of Civil Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.


Abstract
This paper presents a multi-layer finite element for buckling and free vibration analyses of laminated beams based on a higher-order layer-wise theory. An N-layer beam element with (9N + 7) degrees-of-freedom is proposed for analyses. Delamination and slip between the layers are not allowed. Element matrices for the single- and multi-layer beam elements are derived by Lagrange's equations. Buckling loads and natural frequencies are calculated for different end conditions and lamina stacking. Comparisons are made to show the accuracy of proposed element.

Key Words
laminated beams; finite element method; free vibration; buckling; higher-order shear deformation theory

Address
Department of Civil Engineering, Faculty of Engineering, Karadeniz Technical University, Trabzon 61080, Turkey.


Abstract
Static stability is a decisive factor in the design of domes. Stability-related external factors, such as load and supports, are incorporated into structural vulnerability theory by the definition of a relative rate of joint well-formedness (rr). Hence, the instability mechanism of domes can be revealed. To improve stability, an optimization model against instability, which takes the maximization of the lowest rr (rr,min) as the objective and the discrete member sections as the variables, is established with constraints on the design requirements and steel consumption. Optimizations are performed on two real-life Kiewitt-6 model domes with a span of 23.4 m and rise of 11.7 m, which are initially constructed for shaking table collapse test. Well-formedness analyses and stability calculation (via arc-length method) of the models throughout the optimization history demonstrate that this proposed method can effectively enhance rr,min
Key Words
domes; optimization; instability mechanism; well-formedness; shaking table collapse test

Address
(1) Jihong Ye:
The State Key Laboratory for GeoMechanics & Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, China;
(2) Mingfei Lu:
Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education, Southeast University, Nanjing 210018, China.

Abstract
The structural behaviors of cylindrical barns as a specific engineering structure have been considered as a complicated computing process. The structure design against the earthquake load, to protect by using the code, is an urgency avoiding unexpected damages. The situation has been subjected to the applied design method if there would be no failure across the construction procedures. The purpose of the current study is to clarify the behaviors of cylindrical reinforced concrete barns through the analytic methods across the mass and Lagrangian approaches through the whole outcomes comparison indicating that the isoparametric element obtained from the Lagrangian approach has been successfully applied in the barns earthquake analysis when the slosh effects have been discarded. The form of stress distributions is equal with sz closed distributions to one another.

Key Words
analysis of cylindrical barns; earthquake load; added mass; Lagrangian approach; analytical methods

Address
(1) Yousef Zandi:
Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran;
(2) Mahdi Shariati, Aminaton Marto:
Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia;
(3) Mahdi Shariati:
Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran;
(4) Mahdi Shariati, Ali Toghroli:
Department of Civil Engineering, Faculty of engineering, University of Malaya, Kuala Lumpur, Malaysia;
(5) Xing Wei:
Department of Bridge Engineering, School of Civil Engineering, Southwest Jiaotong University, Chengdu, China;
(6) Zeki Karaca:
Department of Civil Engineering, Karadeniz Technichal University, Trabzon, Turkey;
(7) Duy Kien Dao:
Department of Civil Engineering, Ho Chi Minh City University of Technology and Education, 1 Vo Van Ngan street, Thu Duc District, Ho Chi Minh City, Vietnam;
(8) Mir Heydar Hashemi:
Department of Civil Engineering, Faculty of Engineering, Azarbaijan Shahid Madani University, Tabriz, Iran;
(9) Yadollah Sedghi:
Department of Civil Engineering, Qeshm International Branch, Islamic Azad University, Qeshm, Iran;
(10) Karzan Wakil:
University of Human Development, Iraq;
(11) Karzan Wakil:
Information Technology Department, Technical College of Informatics, Sulaimani Polytechnic University, Iraq;
(12) Majid Khorami:
Facultad de Arquitectura y Urbanismo, Universidad Tecnologica Equinoccial, Calle Rumipamba s/n y Bourgeois, Quito, Ecuador.

Abstract
This paper reports the experimental results of three through bolt beam-column connections under pure shear forces using modified push-out tests. The investigated specimens include extended end-plates and six through-bolts connecting square concrete-filled steel tubular column (S-CFST) to steel beams. The main goal of this study is to investigate if and how the mechanical shear connectors, such as steel angles and stud bolts, contribute to the shear transfer mechanisms in the steel-concrete interface of the composite column. The contribution of shear studs and steel angles to improve the shear resistance of steel-concrete interface in through-bolt connections was investigated using tests. The results showed that their contribution is not significant when the beam-column connection is included in the push-out tests. The specimens failed by pure shear of the long bolts, and the ultimate load can be predicted using the shear resistance of the bolts under shear forces. The predicted values of load allowed obtaining a good agreement with the tests results.

Key Words
beam-to-column connection; shear forces; through-bolt connection; steel-concrete interface; mechanical connectors

Address
(1) Silvana De Nardin:
Department of Structural Engineering, University of Sao Paulo, Sao Carlos, Avenida Trabalhador Saocarlense 400, Centro, Sao Carlos-SP - CEP: 13.566-590, Brazil;
(2) Ana Lucia H.C. El Debs:
Department of Civil Engineering, Federal University of Sao Carlos, Rod. Washington Luis km 235 - SP-310 - Sao Carlos, CEP 13565-905, Brazil.

Abstract
In this study, the effect of polyurethane foam filler, in addition to surface layer thickness and core material thickness, on vibration characteristics of sandwich structures was investigated. The manufacturing process was carried out according to the Taguchi method. The natural frequencies and damping ratios of the produced samples were determined experimentally for fixedfree boundary conditions. In addition, solid models were developed for test samples and their finite element analyses were performed with ANSYS® to obtain their natural frequencies and mode shapes. An acceptably good agreement was found with the comparison of experimental results with the numerically obtained ones. The most effective parameters on the vibration characteristics of the sandwich structure were determined by the Taguchi method.

Key Words
honeycomb sandwich structure; polyurethane foam; natural frequency; damping ratio; Taguchi method

Address
(1) Muhammet R. Aydin:
Department of Mechanical Engineering, Iğdır University, 76000, Iğdır, Turkey;
(2) Ömer Gündoğdu:
Department of Mechanical Engineering, Atatürk University, 25240, Erzurum, Turkey.

Abstract
The composite reinforced concrete and steel (RCS) structural systems have larger structural lateral stiffness, higher inherent structural damping, and faster construction speed than either traditional reinforcement concrete or steel structures. In this paper, four RCS subassemblies with or without the RC slab designed following a strong column-weak beam philosophy were constructed and tested under reversed-cyclic loading. Parameters including the width of slab and composite effect of the RC slab and beam were explored. The test results showed that all specimens performed in a ductile manner with plastic hinges formed in the beam ends near the column faces. The seismic responses of composite connections are influenced significantly by different width of slabs. Compared with that of the steel beam without the RC slab, it was found that the load carrying capacity of composite connections with the RC slab increased by 30% on average, and strength degradation, energy dissipation also had better performance, while the ductility of that were almost the same. Furthermore, the contribution of connection deformation to the overall specimen displacement was analyzed and compared. It decreased approximately 10% due to the coupling effect in the columns and beams with the RC slab. Based on the test result, some suggestions are presented for the design of composite RCS joints.

Key Words
reinforced concrete column and steel beam; composite connections; slab; quasi-static test; seismic behavior; capacity; deformation

Address
(1) Liquan Xiong, Jinjie Men, Ruyue Ren, Mengke Lei:
College of Civil Engineering, Xi'an University of Architecture & Technology, 13 Yanta Road, Xi'an, Shaanxi Province, 710055, China;
(2) Liquan Xiong:
Department of Civil Engineering, Chongqing Three Gorges University, 666 Tianxing Road, Wanzhou, Chongqing Municipality, 404120, China.

Abstract
In this research the effect of high strength concrete (HSC) on shear capability of the channel shear connectors (CSC) in the steel concrete composite floor system was estimated experimentally and analytically. The push-out test was carried out for assessing the accurateness of the proposed model (nonlinear and finite element model) for the test specimens. A parametric analysis was conducted for predicting the shear capacity of the connectors (CSC) in the HSC. Eight push-out specimens of different sizes of channels with different high strength concrete were tested under the monotonic loading system. The aim of this study was to evaluate the efficacy of the National Building Code of Canada (NBC) of Canada for analysing the loading abilities of the CSC in the HSC. Using the experimental tests results and verifying the finite element results with them, it was then confirmed by the extended parametric studies that the Canadian Design Code was less efficient for predicting the capacity of the CSC in the HSC. Hence, an alternative equation was formulated for predicting the shear capacity of these connectors during the inclusion of HSC for designing the codes.

Key Words
high strength concrete; channel shear connector; push-out test; finite element analysis; steel concrete composite floor

Address
(1) Masoud Paknahad:
Department of Civil Engineering, Mahallat Institute of Higher Education, Mahallat, Iran;
(2) Mahdi Shariati:
Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran;
(3) Mahdi Shariati:
Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia;
(4) Mahdi Shariati:
Department of Civil Engineering, University of Malaya, 50603, Kuala Lumpur, Malaysia;
(5) Yadollah Sedghi:
Department of Civil Engineering, Qeshm International Branch, Islamic Azad University, Qeshm, Iran;
(6) Mohammad Bazzaz:
Department of Civil, Environmental, and Architectural Engineering, University of Kansas, Lawrence, KS, USA;
(7) Majid Khorami:
Facultad de Arquitectura y Urbanismo, Universidad Tecnologica Equinoccial, Calle Rumipamba s/n y Bourgeois, Quito, Ecuador.

Abstract
In this paper, the effect of matrix cracks on the buckling of a hybrid laminated plate is investigated. The plate is composed of carbon nanotube reinforced functionally graded (CNTR-FG) layers and conventional fiber reinforced composite (FRC) layers. Different distributions of single walled carbon nanotubes (SWCNTs) through the thickness of layers are considered. The cracks are modeled as aligned slit cracks across the ply thickness and transverse to the laminate plane, and the distribution of cracks is assumed statistically homogeneous corresponding to an average crack density. The first-order shear deformation theory (FSDT) is employed to incorporate the effects of rotary inertia and transverse shear deformation, and the meshless kp-Ritz method is used to obtain the buckling solutions. Detailed parametric studies are conducted to investigate the effects of matrix crack density, CNTs distributions, CNT volume fraction, plate aspect ratio and plate length-to-thickness ratio, boundary conditions and number of layers on buckling behaviors of hybrid laminated plates containing CNTR-FG layers.

Key Words
buckling; carbon nanotube-reinforced functionally graded composites; matrix crack; meshless kp-Ritz method

Address
School of Sciences, Nanjing University of Science and Technology, Nanjing 210094, China.


Abstract
The differential quadrature (DQ) and teaching-learning based optimization (TLBO) methods are coupled to introduce a hybrid numerical method for maximizing fundamental natural frequency of laminated composite skew plates. The fiber(s) orientations are selected as design variable(s). The first-order shear deformation theory (FSDT) is used to obtain the governing equations of the plate. The equations of motion and the related boundary conditions are discretized in space domain by employing the DQ method. The discretized equations are transferred from the time domain into the frequency domain to obtain the fundamental natural frequency. Then, the DQ solution is coupled with the TLBO method to find the maximum frequency of the plate and its related optimum stacking sequences of the laminate. Convergence and applicability of the proposed method are shown and the optimum fundamental frequency parameter of the plates with different skew angle, boundary conditions, number of layers and aspect ratio are obtained. The obtained results can be used as a benchmark for further studies.

Key Words
a hybrid numerical method; differential quadrature method; teaching-learning based optimization method; laminated composite skew plates

Address
(1) Ali R. Vosoughi:
Department of Mechanical Engineering, School of Engineering, Persian Gulf University, Bushehr 7516913798, Iran;
(2) Parviz Malekzadeh:
Department of Mechanical Engineering, School of Engineering, Persian Gulf University, Bushehr 7516913798, Iran;
(3) Umut Topal:
Department of Civil Engineering, Faculty of Technology, Karadeniz Technical University, Trabzon, Turkey;
(4) Tayfun Dede:
Department of Civil Engineering, Karadeniz Technical University, 61080 Trabzon, Turkey.


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