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CONTENTS
Volume 24, Number 6, August30 2017
 

Abstract
High strength preloadable bolt assemblies are commonly adopted in beam-to-column bolted connections. Nowadays, two systems of high strength preloadable grade 10.9 bolt assembly are recommended in Europe for structural applications, namely HR and HV, which are characterized by different failure modes. Recently, experimental tests performed on HR and HV bolt assemblies highlighted that the type of bolt assembly may significantly influence the joint response. Therefore, the accuracy of numerical modelling of bolt assemblies is crucial to simulate effectively the non-linear behaviour of bolted joints with either failure mode 2 or mode 3 of the bolt rows. In light of these considerations, this present paper describes and discusses some modelling criteria for both HR and HV bolts to be implemented in 3D finite element models by finite element analysis and structural designers. The comparison between the calibrated models and experimental results shows the accuracy of the proposed assumptions in simulating all stages of assembly tensile response.

Key Words
high strength preloadable bolt; HR; HV; modelling criteria; bolted connections

Address
(1) Mario D'Aniello, Raffaele Landolfo:
Department of Structures for Engineering and Architecture, University of Naples "Federico II", via Forno Vecchio, 36 – Napoli 80134, Italy;
(2) David Cassiano:
ISISE, University of Coimbra, Polo II – R. Luís Reis Santos, 3030-788 Coimbra, Portugal.

Abstract
In the present work, an analytical solution for the static analysis of laminated composites, functionally graded and sandwich singly and doubly curved panels on the rectangular plan-form, subjected to uniformly distributed transverse loading is presented. Mathematical formulation is based on the higher order shear deformation theory and principle of virtual work is applied to derive the equations of equilibrium subjected to small deformation. A solution methodology based on the fast converging finite double Chebyshev series is used to solve the linear partial differential equations along with the simply supported boundary condition. The effect of span to thickness ratio, radius of curvature to span ratio, stacking sequence, power index are investigated. The accuracy of the solution is checked by the convergence study of non-dimensional central deflection and moments. Present results are compared with those available in the literature.

Key Words
analytical solution; higher order shear deformation theory; doubly curved panels; Chebyshev polynomial

Address
Department of Applied Mechanics, MNNIT, Allahabad, U.P., 211004. India.


Abstract
In this paper, two powerful analytical methods called Variational Approach (VA) and Hamiltonian Approach (HA) are used to solve high nonlinear non-Natural vibration problems. The presented approaches are works well for the whole range of amplitude of the oscillator. The first iteration of the approaches leads us to high accurate solution. Numerical results are also presented by using Runge-Kutta's [RK] algorithm. The full comparison between the presented approaches and the numerical ones are shown in figures. The effects of important parameters on the response of nonlinear behavior of the systems are studied completely. Finally, the results show that the Variational Approach and Hamiltonian approach are strong enough to prepare easy analytical solutions.

Key Words
Hamiltonian Approach (HA); Variational Approach (VA); nonlinear vibration; analytical method

Address
(1) Mahmoud Bayat:
Young Researchers and Elite Club, Roudehen Branch, Islamic Azad University, Roudehen, Iran;
(2) Iman Pakar:
Young Researchers and Elite Club, Mashhad Branch, Islamic Azad University, Mashhad, Iran.

Abstract
A GFRP-concrete composite bridge deck is presented in this paper. This composite deck is composed of concrete and a GFRP plate and is connected by GFRP perfobond (PBL) shear connectors with penetrating GFRP rebar. There are many outstanding advantages in mechanical behavior, corrosion resistance and durability of this composite deck over conventional reinforced concrete decks. To analyze the shear and flexural performance of this GFRP-concrete composite deck, a static loading experiment was carried out on seven specimens. The failure modes, strain development and ultimate bearing capacity were thoroughly examined. Based on elastic theory and strain-based theory, calculation methods for shear and flexural capacity were put forward and revised. The comparison of tested and theoretical capacity results showed that the proposed methods could effectively predict both the flexural and shear capacity of this composite deck. The ACI 440 methods were relatively conservative in predicting flexural capacity and excessively conservative in predicting shear capacity of this composite deck. The analysis of mechanical behavior and the design method can be used for the design of this composite deck and provides a significant foundation for further research.

Key Words
GFRP-concrete composite deck; flexural performance; shear performance; design method; experimental study

Address
School of Civil Engineering, Xi'an University of Architecture & Technology, Xi'an, Shaanxi 710055, China.


Abstract
The constitutive relation is an important factor in analysis of confined concrete in composite structures. In order to propose a constitutive model for nonlinear analysis of confined concrete, lateral restraint mechanism of confined concrete is firstly analyze to study the generalities. As the foundation of the constitutive model, peak stress and peak strain is the first step in research. According to the generalities and the Twin Shear Unified Strength Theory, a novel unified equation for peak stress and peak strain are established. It is well coincident with experimental results. Based on the general constitutive relations and the unified equation for peak stress and peak strain, we propose a unified and convenient constitutive model for confined concrete with fewer material parameters. Two examples involved with steel tube confined concrete and hoop-confined concrete are considered. The proposed constitutive model coincides well with the experimental results. This constitutive model can also be extended for nonlinear analysis to other types of confined concrete.

Key Words
confined concrete; lateral restraint force; the Twin Shear Unified Strength Theory; constitutive model

Address
Department of Civil Engineering, Xi'an University of Architecture and Technology, Yanta Road, Xi'an, Shaanxi 710055, China.


Abstract
The current study addresses the local buckling analysis of an infinite thin rectangular symmetrically laminated composite plate restrained by a tensionless Winkler foundation and subjected to uniform in-plane shear loading. An analytic method (i.e., one-dimensional mathematical method) is used to achieve the analytical solution estimate of the contact buckling coefficient. In addition, to study the effect of ply angle and foundation stiffness on the critical buckling coefficients for the laminated composite plates, the parametric studies are implemented. Moreover, the convergence for finite element (FE) mesh is analysed, and then the examples in the parametric study are validated by the FE analysis. The results show that the FE analysis has a good agreement with the analytical solutions. Finally, an example with the analytical solution and FE analysis is presented to demonstrate the availability and feasibility of the presented analytical method.

Key Words
buckling coefficient; contact buckling; finite element analysis; Winkler foundation; laminated composite plate

Address
School of Natural and Built Environments, University of South Australia, Adelaide, SA 5095, Australia.


Abstract
In the present work, by considering the agglomeration effect of single-walled carbon nanotubes, free vibration characteristics of functionally graded (FG) nanocomposite sandwich plates resting on Pasternak foundation are presented. The volume fractions of randomly oriented agglomerated single-walled carbon nanotubes (SWCNTs) are assumed to be graded in the thickness direction. To determine the effect of CNT agglomeration on the elastic properties of CNT-reinforced composites, a two-parameter micromechanical model of agglomeration is employed. In this research work, an equivalent continuum model based on the Eshelby-Mori-Tanaka approach is employed to estimate the effective constitutive law of the elastic isotropic medium (matrix) with oriented straight CNTs. The 2-D generalized differential quadrature method (GDQM) as an efficient and accurate numerical tool is used to discretize the equations of motion and to implement the various boundary conditions. The proposed rectangular plates have two opposite edges simply supported, while all possible combinations of free, simply supported and clamped boundary conditions are applied to the other two edges. The benefit of using the considered power-law distribution is to illustrate and present useful results arising from symmetric and asymmetric profiles. The effects of twoparameter elastic foundation modulus, geometrical and material parameters together with the boundary conditions on the frequency parameters of the laminated FG nanocomposite plates are investigated. It is shown that the natural frequencies of structure are seriously affected by the influence of CNTs agglomeration. This study serves as a benchmark for assessing the validity of numerical methods or two-dimensional theories used to analysis of laminated plates.

Key Words
Mori-Tanaka approach; two-parameter micromechanical model of agglomeration; sandwich structures; 2D generalized differential quadrature method; vibration analysis

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


Abstract
The present paper studies the stability analysis of the continuously graded CNT-Reinforced Composite (CNTRC) panel stiffened by rings and stringers. The Stiffened Panel (SP) subjected to axial and lateral loads is reinforced by agglomerated CNTs smoothly graded through the thickness. A two-parameter Eshelby-Mori-Tanaka (EMT) model is adopted to derive the effective material moduli of the CNTRC. The stability equations of the CNRTC SP are obtained by means of the adjacent equilibrium criterion. Notwithstanding most available literature in which the stiffener effects were smeared out over the respective stiffener spacing, in the present work, the stiffeners are modeled as Euler-Bernoulli beams. The Generalized Differential Quadrature Method (GDQM) is employed to discretize the stability equations. A numerical study is performed to investigate the influences of different types of parameters involved on the critical buckling of the SP reinforced by agglomerated CNTs. The results achieved reveal that continuously distributing of CNTs adjacent to the inner and outer panel's surface results in improving the stiffness of the SP and, as a consequence, inclining the critical buckling load. Furthermore, it has been concluded that the decline rate of buckling load intensity factor owing to the increase of the panel angle is significantly more sensible for the smaller values of panel angle.

Key Words
panel structure; buckling stability; Generalized Differential Quadrature Method (GDQM); polymer matrix; two-parameter Eshelby-Mori-Tanaka (EMT); carbon-nanotubes; third-order shear deformation theory

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


Abstract
A steel slit shear wall has vertical slits and when it is under lateral loads, the section between these slits has double-curvature deformation, and by forming a flexural plastic hinge at the end of the slit, it dissipates the energy on the structure. In this article, Experimental, numerical and analytical analyses are performed to study the effect of slit shape and edge stiffener on the behavior of steel slit shear wall. Seismic behavior of three models with different slit shapes and two models with different edge stiffener shapes are studied and compared. Hysteresis curves, energy dissipation, out of plane buckling, initial stiffness and strength are discussed and studied. The proposed slit shape reduces the initial stiffness, increases the strength and energy dissipation. Also, edge stiffener shape increases the initial stiffness significantly.

Key Words
steel slit shear wall; analytical analysis; energy dissipation; hysteresis curve

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


Abstract
This paper aims to investigate the strength degradation of reinforced concrete piers wrapped with steel plates which corrode at the pier base by employing a three dimensional elasto-plastic finite element formulation. The prediction accuracy of the employed finite element analysis method is firstly verified by comparing the analytical results with test results. Then, a series of parametric studies is carried out to investigate the effects of steel plate's corrosion position along width direction, corrosion depth along plate thickness, corrosion range along width direction, and steel plate-concrete bonding degradation on the strength of the piers. It is observed that the strength degradation of the piers is closely related to steel plate's corrosion position, corrosion depth and corrosion range in the case of local corrosion on the webs. In contrast, when the base of flanges corrodes, the strength degradation of the piers is only related to steel plate's corrosion depth and corrosion range, and the influence of corrosion position on the strength degradation is very gentle. Furthermore, the strength of the piers decreases with the degradation of steel plate-concrete bonding behavior. Finally, the maximum strength of the piers obtained from numerical analysis corresponding to different bonding behavior is compared with theoretical results within an accepted error.

Key Words
bridge engineering; reinforced concrete pier; steel plate; local corrosion; steel plate-concrete bonding behavior; strength degradation

Address
(1) Shengbin Gao:
State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China;
(2) Shengbin Gao, Daxu Zhang:
Department of Civil Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China;
(3) Jie Ni:
The IT Electronic 11th Design & Research Institute, Shanghai, 200233, China;
(4) Hanbin Ge:
Department of Civil Engineering, Meijo University, Nagoya, 468-8502, Japan.

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