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CONTENTS
Volume 26, Number 5, March10 2018
 

Abstract
In this paper the time-dependent creep analysis of a thick-walled FG cylinder with finite length subjected to axisymmetric mechanical and thermal loads are presented. First order shear deformation theory (FSDT) is used for description of displacement components. Inner and outer temperatures and outer pressure are considered as thermo-mechanical loadings. Both thermal and mechanical loadings are assumed variable along the axial direction using the sinusoidal distribution. To find temperature distribution, two dimensional heat transfer equation is solved using the required boundary conditions. The energy method and Euler equations are employed to reach final governing equations of the cylinder. After determination of elastic stresses and strains, the creep analysis can be performed based on the Yang method. The results of this research indicate that the boundaries have important effects on the responses of the cylinder. The effect of important parameters of this analysis such as variable loading, non-homogeneous index of functionally graded materials and time of creep is studied on the behaviors of the cylinder.

Key Words
creep analysis; first order shear deformation theory; functionally graded materials; cylindrical shell

Address
Department of Solid Mechanic, Faculty of Mechanical Engineering, University of Kashan, Kashan 87317-51167, Iran.


Abstract
Progressive building collapse occurs when failure of a structural component leads to the failure and collapse of surrounding members, possibly promoting additional failure. Global system collapse will occur if the damaged system is unable to reach a new static equilibrium configuration. The most common type of primary failure which led to the progressive collapse phenomenon, is the sudden removal of a column by various factors. In this study, a method is proposed to prevent progressive collapse phenomena in structures subjected to removal of a single column. A vierendeel peripheral frame at roof level is used to redistribute the removed column's load on other columns of the structure. For analysis, quasi-static approach is used which considers various load combinations. This method, while economically affordable is easily applicable (also for new structures as well as for existing structures and without causing damage to their architectural requirements). Special emphasis is focused on the evolution of vertical displacements of column removal point. Even though additional stresses and displacements are experienced by removal of a structural load bearing column, the proposed method considerably reduces the displacement at the mentioned point and prevents the collapse of the structural frame.

Key Words
steel moment frames; progressive collapse; structural failures ; vierendeel frame; column removal

Address
Department of Civil Engineering, Sharif University of Technology, Tehran, Iran.


Abstract
In this paper, a refined higher-order shear deformation theory including the stretching effect is developed for the analysis of bending analysis of the simply supported functionally graded (FG) sandwich plates resting on elastic foundation. This theory has only five unknowns, which is even less than the other shear and normal deformation theories. The theory presented is variationally consistent, without the shear correction factor. 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
FG sandwich plates; new plate theory; bending; stretching effect; analytical modeling

Address
(1) Tarek Houari, Mohamed Benguediab:
Département de Génie Mécanique, Faculté de Technologie, Université Sidi Bel Abbes, Algérie;
(2) Aicha Bessaim, Mohammed Sid Ahmed Houari:
Département de Génie Civil, Faculté des Sciences et de la Technologie, Université Mustapha Stambouli Mascara, Algeria;
(3) Aicha Bessaim, Mohammed Sid Ahmed Houari, Abdelouahed Tounsi:
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
(4) Aicha Bessaim, Mohammed Sid Ahmed Houari:
Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics, Université de Sidi Bel Abbes, Faculté de Technologie, Département de génie civil, Algeria;
(5) Abdelouahed Tounsi:
Laboratoire de Modélisation et Simulation Multi-échelle, Faculté des Sciences, Département de Physique, Université de Sidi Bel Abbes, Algeria.

Abstract
This study develops and numerically verifies an innovative seismically resilient bracing system. The proposed selfcentering tension-only brace (SC-TOB) is composed of a tensioning system to provide a self-centering response, a frictional device for energy dissipation, and a high-strength steel cable as a bracing element. It is considered to be an improvement over the traditional self-centering braces in terms of lightness, high bearing capacity, load relief, and double-elongation capacity. In this paper, the mechanics of the system are first described. Governing equations deduced from the developed analytical model to predict the behavior of the system are then provided. The results from a finite element validation confirm that the SC-TOB performs as analytically predicted. Key parameters including the activation displacement and load, the self-centering parameter, and equivalent viscous damping are investigated, and their influences on the system behavior are discussed. Finally, a design procedure considering controlled softening behavior is developed and illustrated through a design example.

Key Words
self-centering brace; tension-only brace; residual deformation; energy dissipation; pre-tension

Address
(1) Pei Chi, Tong Guo:
College of Civil Engineering, Nanjing Tech University, 30 South Puzhu Road, Nanjing 211816, China;
(2) Pei Chi, Dafu Cao:
College of Civil Science and Engineering, Yangzhou University, 88 South University Avenue, Yangzhou 225009, China;
(3) Yang Peng, Jun Dong:
College of Civil Engineering, Nanjing Tech University, 30 South Puzhu Road, Nanjing 211816, China.

Abstract
Although a lot of experimental and analytical investigations have been carried out for steel bridge piers made of SS400 and SM490, the formulas available for SS400 and SM490 are not suitable for evaluating ultimate load and deformation capacities of steel bridge piers made of high strength steel (HSS) SM570. The effect of various parameters is investigated in this paper, including plate width-to-thickness ratio, column slenderness ratio and axial compression force ratio, on the ultimate load and deformation capacities of steel bridge box piers made of SM570 steel subjected to cyclic loading. The elasto-plastic behavior of the steel bridge piers under cyclic loads is simulated through plastic large deformation finite element analysis, in which a modified two-surface model (M2SM) including cyclic hardening is employed to trace the material nonlinearity. An extensive parametric study is conducted to study the influences of structural parameters on the ultimate load and deformation capacities. Based on these analytical investigations, new formulas for predicting ultimate load and deformation capacities of steel bridge piers made of SM570 are proposed. This study extends the ultimate load and deformation capacities evaluation of steel bridge piers from SS400, SM490 steels to SM570 steel, and provides some useful suggestions.

Key Words
steel bridge pier; ultimate load; deformation capacity; high strength steel; two-surface model

Address
(1) Lan Kang:
School of Civil Engineering and Transportation, South China University of Technology, Guangzhou, 510640, China;
(2) Motoya Suzuki, Hanbin Ge:
Department of Civil Engineering, Meijo University, Nagoya, 468-8502, Japan;
(3) Lan Kang:
State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou, Guangdong Province, 510641, China.

Abstract
A calculation method was presented to calculate the deflection of GFRP-concrete-steel beams with full or partial shear connections. First, the sectional analysis method was improved by considering concrete nonlinearity and shear connection stiffness variation along the beam direction. Then the equivalent slip strain was used to take into consideration of variable crosssections. Experiments and nonlinear finite element analysis were performed to validate the calculation method. The experimental results showed the deflection of composite beams could be accurately predicted by using the theoretical model or the finite element simulation. Furthermore, more finite element models were established to verify the accuracy of the theoretical model, which included different GFRP plates and different numbers of shear connectors. The theoretical results agreed well with the numerical results. In addition, parametric studies using theoretical method were also performed to find out the effect of parameters on the deflection. Based on the parametric studies, a simplified calculation formula of GFRP-concrete-steel composite beam was exhibited. In general, the calculation method could provide a more accurate theoretical result without complex finite element simulation, and serve for the further study of continuous GFRP-concrete-steel composite beams.

Key Words
GFRP-concrete-steel; composite beam; deflection; finite element; slip; variable cross-sections

Address
Department of Bridge Engineering, School of Transportation, Southeast University, Nanjing, China.


Abstract
Vibration analysis of deep curved FG nano-beam has been carried out based on modified couple stress theory. Material properties of curved Timoshenko beam are assumed to be functionally graded in radial direction. Governing equations of motion and related boundary conditions have been obtained via Hamilton's principle. In a parametric study, influence of length scale parameter, aspect ratio, gradient index, opening angle, mode number and interactive influences of these parameters on natural frequency of the beam, have been investigated. It was found that, considering geometrical deepness term leads to an increase in sensitivity of natural frequency about variation of aforementioned parameters.

Key Words
deep curved nano beam; Timoshenko beam model; functionally graded material; modified couple stress; vibration analysis

Address
Smart Structures and New Advanced Materials Laboratory, Department of Mechanical Engineering, University of Zanjan, Zanjan, Iran.


Abstract
Flush end-plate (FEP) beam-to-column joints are commonly used for gravity load resisting parts in steel multistorey buildings. However, in seismic resisting structures FEP joints should also provide rotation capacity consistent with the global structural displacements. The current version of EN1993-1-8 recommends a criterion aiming at controlling the thickness of the end-plate in order to avoid brittle failure of the connection, which has been developed for monotonic loading conditions assuming elastic-perfectly plastic behaviour of the connection's components in line with the theory of the component method. Hence, contrary to the design philosophy of the hierarchy of resistances implemented in EN1998-1, the over strength and the hardening of the plastic components are not directly accounted for. In light of these considerations, this paper describes and discusses the results obtained from parametric finite element simulations aiming at investigating the moment-rotation response of FEP joints under cyclic actions. The influence of bolt diameter, thickness of end-plate, number of bolt rows and shape of beam profile on the joint response is discussed and design requirements are proposed to enhance the ductility of the joints.

Key Words
cyclic loading; beam-to-column joints; FEM; flush end-plate; seismic design

Address
(1) David Cassiano:
Constructure, Ltd, Unit D 15 Bell Yard Mews, London SE1 3TY, United Kingdom;
(2) Mario D'\'Aniello:
Department of Structures for Engineering and Architecture, University of Naples "Federico II", via Forno Vecchio, 36 — Napoli 80134, Italy;
(3) Carlos RebelO:
ISISE, University of Coimbra, Polo II . R. Luis Reis Santos, 3030-788 Coimbra, Portugal.

Abstract
In order to improve the efficiency of the Reinforced Concrete, RC, structures against progressive collapse, this paper proposes a procedure using alternate path and specific local resistance method to resist progressive collapse in intermediate RC frame structures. Cap truss consists of multiple trusses above a suddenly removed structural element to restrain excessive collapse and provide an alternate path. Steel strut is used as a brace to resist compressive axial forces. It is similar to knee braces in the geometry, responsible for enhancing ductility and preventing shear force localization around the column. In this paper, column removals in the critical position at the first story of two 5 and 10-story regular buildings strengthened using steel strut or cap truss are studied. Based on nonlinear dynamic analysis results, steel strut can only decrease vertical displacement due to sudden removal of the column at the first story about 23%. Cap truss can reduce the average vertical displacement and column axial force transferred to adjacent columns for the studied buildings about 56% and 61%, respectively due to sudden removal of the column. In other words, using cap truss, the axial force in the removed column transfers through an alternate path to adjacent columns to prevent local or general failure or to delay the progressive collapse occurrence.

Key Words
progressive collapse; reinforced concrete (RC) frame; alternate load path method; steel strut; cap truss; nonlinear dynamic analysis

Address
(1) Seyed Mehdi Zahrai:
Center of Excellence for Engineering and Management of Infrastructures, School of Civil Engineering, College of Engineering, The University of Tehran, Tehran, Iran;
(2) Alireza Ezoddin:
Faculty of Civil Engineering, Semnan University, Semnan, Iran and lecturer, Department of Civil Engineering, Semnan Branch, Technical and Vocational University (TVU), Semnan, Iran.

Abstract
In this study, based on the three-dimensional theory of elasticity, free vibration characteristics of sandwich sectorial plates with multiwalled carbon nanotube-(MWCNT)-reinforced composite core are considered. Modified Halpin-Tsai equation is used to evaluate the Young's modulus of the MWCNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. The exponential shape factor modifies the Halpin-Tsai equation from expressing a straight line to a nonlinear one in the MWCNTs wt% range considered. In this paper, free vibration of thick functionally graded sandwich annular sectorial plates with simply supported radial edges and different circular edge conditions including simply supported-clamped, clamped-clamped, and free-clamped is investigated. A semi-analytical approach composed of twodimensional differential quadrature method and series solution are adopted to solve the equations of motion. The material properties change continuously through the core thickness of the plate, which can vary according to a power-law, exponentially, or any other formulations in this direction. This study serves as a benchmark for assessing the validity of numerical methods or two-dimensional theories used to analysis of laminated sectorial plates.

Key Words
sandwich sectorial plates; vibration; modified Halpin-Tsai equation; three-dimensional theory of elasticity

Address
Young Researchers and Elite Club, Islamshahr Branch, Islamic Azad University, Islamshahr, Iran.



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