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CONTENTS
Volume 32, Number 4, August25 2019
 

Abstract
This study aims to accurately predict the first ply failure loads of laminated composite hypar shell roofs with different boundary conditions. The geometrically nonlinear finite element method (FEM) is used to analyse different symmetric and anti-symmetric, cross and angle ply shells. The first ply failure loads are obtained through different well-established failure criteria including Puck\'s criterion along with the serviceability criterion of deflection. The close agreement of the published and present results for different validation problems proves the correctness of the finite element model used in the present study. The effects of edge conditions on first ply failure behavior are discussed critically from practical engineering point of view. Factor of safety values and failure zones are also reported to suggest design and non-destructive monitoring guidelines to practicing engineers. Apart from these, the present study indicates the rank wise relative performances of different shell options. The study establishes that the angle ply laminates in general perform better than the cross ply ones. Among the stacking sequences considered here, three layered symmetric angle ply laminates offer the highest first ply failure load. The probable failure zones on the different shell surfaces, identified in this paper, are the areas where non-destructive health monitoring may be restricted to. The contributions made through this paper are expected to serve as important design aids to engineers engaged in composite hypar shell design and construction.

Key Words
composite; finite element method (FEM); hypar shell roofs; first ply failure; nonlinear analysis

Address
Department of Civil Engineering, Jadavpur University, Kolkata-700032, India.


Abstract
With the aim to put forward the analytical model for calculating the shear capacity of precast steel reinforced concrete (PSRC) beams, a static test on two full-scale PSRC specimens was conducted under four-point loading, and the failure modes and strain developments of the specimens were critically investigated. Based on the test results, a modified truss-arch model was proposed to analyze the shear mechanisms of PSRC and cast-in-place SRC beams. In the proposed model, the overall shear capacity of PSRC and cast-in-place SRC beams can be obtained by combining the shear capacity of encased steel shape with web concrete determined by modified Nakamura and Narita model and the shear capacity of reinforced concrete part determined by compatible truss-arch model which can consider both the contributions of concrete and stirrups to shear capacity in the truss action as well as the contribution of arch action through compatibility of deformation. Finally, the proposed model is compared with other models from JGJ 138 and AISC 360 using the available SRC beam test data consisting of 75 shear-critical PSRC and SRC beams. The results indicate that the proposed model can improve the accuracy of shear capacity predictions for shear-critical PSRC and cast-in-place SRC beams, and relatively conservative results can be obtained by the models from JGJ 138 and AISC 360.

Key Words
steel reinforced concrete beams; precast concrete; shear capacity; modified truss-arch model; experimental study

Address
(1) Yong Yang, Yicong Xue, Yunlong Yu:
School of Civil Engineering, Xi'an University of Architecture and Technology, Shaanxi, China;
(2) Yicong Xue:
School of Natural and Built Environment, Queen's University Belfast, Northern Ireland, UK;
(3) Yunlong Yu:
Key Lab of Structure and Earthquake Resistance, Shaanxi, China.

Abstract
Despite the rapid advancement in computing resources, many real-life design and optimization problems in structural engineering involve huge computation costs. To counter such challenges, approximate models are often used as surrogates for the highly accurate but time intensive finite element models. In this paper, surrogates for first-order shear deformation based finite element models are built using a polynomial regression approach. Using statistical techniques like Box-Cox transformation and ANOVA, the effectiveness of the surrogates is enhanced. The accuracy of the surrogate models is evaluated using statistical metrics like R2, R2adj, R2pred, and Q2F3. By combining these surrogates with nature-inspired multi-criteria decision-making algorithms, namely multi-objective genetic algorithm (MOGA) and multi-objective particle swarm optimization (MOPSO), the optimal combination of various design variables to simultaneously maximize fundamental frequency and frequency separation is predicted. It is seen that the proposed approach is simple, effective and good at inexpensively producing a host of optimal solutions.

Key Words
FE-surrogate; metamodel; multi-objective genetic algorithm (MOGA); multi-objective particle swarm optimization (MOPSO); pareto front

Address
(1) Kanak Kalita:
Department of Mechanical Engineering, Vel Tech Rangarajan Dr. Sagunthala R&D Institute of Science and Technology, Avadi, 600 062, India;
(2) Partha Dey:
Department of Mechanical Engineering, Academy of Technology, Adisaptagram, Hooghly 712 121, India;
(3) Milan Joshi:
Department of Applied Science & Humanities, SVKM's NMIMS Mukesh Patel School of Technology Management & Engineering, Shirpur 425 405, India;
(4) Salil Haldar:
Department of Aerospace Engineering and Applied Mechanics, Indian Institute of Engineering, Science and Technology, Howrah 711 103, India.

Abstract
Running safety and ride comfort of high speed railway largely depend on the track geometry that is dependent on the bridge deformation. This study presents a theoretical study on mapping the bridge vertical deformations to the change of track geometry. Analytical formulae are derived through the theoretical analysis to quantify the track geometry change, and validated against the finite element analysis and experimental data. Based on the theoretical formulae, parametric studies are conducted to evaluate the effects of key parameters on the track geometry of a high speed railway. The results show that the derived formulae provide reasonable prediction of the track geometry change under various bridge vertical deformations. The rail deflection increases with the magnitude of bridge pier settlement and vertical girder fault. Increasing the stiffness of the fasteners or mortar layer tends to cause a steep rail deformation curve, which is undesired for the running safety and ride comfort of high-speed railway.

Key Words
analytical model; bridge vertical deformation; high-speed railway; mapping relationship; track deformation; track geometry

Address
(1) Hongye Gou, Zhiwen Ran, Longcheng Yang, Yi Bao, Qianhui Pu:
Department of Bridge Engineering, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China;
(2) Hongye Gou:
Key Laboratory of High-Speed Railway Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China;
(3) Hongye Gou:
Department of Civil, Environmental and Ocean Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, USA.

Abstract
In tied-arch bridges, the way the arch and the deck are connected may become crucial. The deck is usually suspended from hangers made out of steel pinned cables capable of resisting axial forces only. However, a proper structural response may be ensured by fixing and stiffening the hangers in order to resist, additionally, shear forces and bending moments. Thus, this paper studies the effect of different pinned and stiffened hanger arrangements on the structural behavior of the tied-arch bridges, with the intention of providing designers with useful tools at the early steps of design. Longitudinally and transversally stiffened hangers (and the effect of hinges at the hangers and their locations) are studied separately because the in-plane and the out-of-plane behavior of the bridge are uncoupled due to its symmetry. As a major conclusion, regarding the in-plane behavior, hangers composed of cables (either with vertical, Nielsen-Lohse or network arrangements) are recommended due to its low cost and ease of erection. Alternatively, longitudinally stiffened hangers, fixed at both ends, can be used. Regarding the out-of-plane behavior, and in addition to three-dimensional arrangements of cables, of limited effectiveness, transversally stiffened hangers fixed at both ends are the most efficient arrangement. A configuration almost as efficient and, additionally, cheaper and easier to build can be achieved by locating a hinge at the end corresponding to the most flexible structural element (normally the arch). Its efficiency is further improved if the cross-section tapers from the fixed end to the pinned end.

Key Words
arch bridge; stiffened hanger; hinge; cable arrangement; preliminary design; conceptual design

Address
Civil Engineering Department, Universidad Politécnica de Cartagena (UPCT), Paseo Alfonso XIII, 52, Cartagena 30203, Spain.

Abstract
Exposed column base connections are used in low- to mid-rise steel moment resisting frames. This paper is to investigate the effect of the base plate thickness on the exposed column base connection strength, stiffness, and energy dissipation. Five specimens with different base plate thickness were numerically modelled using ABAQUS software. The numerical model is able to reproduce the key characteristics of the experimental response. Based on the numerical analysis, the critical base plate thickness to identify the base plate and anchor rod yield mechanism is proposed. For the connection with base plate yield mechanism, the resisting moment is carried by the flexural bending of the base plate. Yield lines in the base plate on the tension side and compression side are illustrated, respectively. This type of connection exhibits a relatively large energy dissipation. For the connection with anchor rod yield mechanism, the moment is resisted through a combination of bearing stresses of concrete foundation on the compression side and tensile forces in the anchor rods on the tension side. This type of connection exhibits self-centering behavior and shows higher initial stiffness and bending strength. In addition, the methods to predict the moment resistance of the connection with different yield mechanisms are presented. And the evaluated moment resistances agree well with the values obtained from the FEM model.

Key Words
exposed column base; base plate thickness; anchor rod yield mechanism; base plate yield mechanism; finite element analysis

Address
(1) Yao Cui:
State Key Laboratory of Coastal and Offshore Engineering, Faculty of Infrastructure Engineering, Dalian University of Technology, No. 2 Linggong-road, Dalian 116024, P.R. China;
(2) Fengzhi Wang, Hao Li:
School of Civil Engineering, Faculty of Infrastructure Engineering, Dalian University of Technology, No. 2 Linggong-road, Dalian 116024, P.R. China;
(3) Satoshi Yamada:
Institute of Innovative Research, Tokyo Institute of Technology, J2-21, Tokyo Institute of Technology, 4259 Nagatsuda, Midori-ku, Yokohama, Japan.

Abstract
In this paper, an analytical approach for the free vibration analysis of spiral stiffened functionally graded (SSFG) cylindrical shells is investigated. The SSFG shell is resting on linear and non-linear elastic foundation with damping force. The elastic foundation for the linear model is according to Winkler and Pasternak parameters and for the non-linear model, one cubic term is added. The material constitutive of the stiffeners is continuously changed through the thickness. Using the Galerkin method based on the von Kármán equations and the smeared stiffeners technique, the non-linear vibration problem has been solved. The effects of different geometrical and material parameters on the free vibration response of SSFG cylindrical shells are adopted. The results show that the angles of stiffeners and elastic foundation parameters strongly effect on the natural frequencies of the SSFG cylindrical shell.

Key Words
FG cylindrical shells; non-linear free vibration; spiral stiffeners; damping; elastic foundation

Address
Faculty of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, Iran.


Abstract
The mechanical response of concrete-filled steel tubular (CFST) columns subjected to pure compression or uniaxial bending was studied in depth over the last decades. However, the available research results on CFST columns under biaxial bending are still scarce and the lack of experimental tests for this loading situation is evident. At the same time, the design provisions in Eurocode 4 Part 1.1 for verifying the stability of CFST columns under biaxial bending make use of a simplistic interaction curve, which needs to be revised. This paper presents the outcome of a numerical investigation on slender CFST columns subjected to biaxial bending. Eccentricities differing in minor and major axis, as well as varying end moment ratios are considered in the numerical model. A parametric study is conducted for assessing the current design guidelines of EN1994-1-1. Different aspect ratios, member slenderness, reinforcement ratios and load eccentricities are studied, covering both constant and variable bending moment distribution. The numerical results are subsequently compared to the design provisions of EN1994-1-1, showing that the current interaction equation results overly conservative. An alternative interaction equation is developed by the authors, leading to a more accurate yet conservative proposal.

Key Words
biaxial bending; non-constant bending moment; concrete-filled steel tubular columns; finite element analysis; parametric studies; Eurocode 4

Address
(1) Ana Espinós, Manuel L. Romero:
Instituto de Ciencia y Tecnología del Hormigón (ICITECH), Universitat Politècnica de València, Valencia, Spain;
(2) Vicente Albero:
Department of Mechanical Engineering and Construction, Universitat Jaume I, Castellón, Spain;
(3) Maximilian Mund, Patrick Meyer, Peter Schaumann:
Institute for Steel Construction, Leibniz Universitaet Hannover, Germany.

Abstract
This paper introduces an improved numerical model which can consider the bond-slip effect in steel-concrete composite structures without taking double nodes to minimize the complexity in constructing a finite element model. On the basis of a linear partial interaction theory and the use of the bond link element, the slip behavior is defined and the equivalent modulus of elasticity and yield strength for steel is derived. A solution procedure to evaluate the slip behavior along the interface of the composite flexural members is also proposed. After constructing the transfer matrix relation at an element level, successive application of the constructed relation is conducted from the first element to the last element with the compatibility condition and equilibrium equations at each node. Finally, correlation studies between numerical results and experimental data are conducted with the objective of establishing the validity of the proposed numerical model.

Key Words
composite structure; bond-slip; slip analysis; flexural member; FEM

Address
Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea.


Abstract
The use of shear studs usually placed in the form of mechanical shear connectors makes it possible to adopt composite steel-concrete structures in various structures, and steel-concrete plate composite (SCP) is being seriously considered for the installation of storage tanks exposed to harsh environments. However, manufacturing of SCP must be based on the application of existing design guidelines which require very close arrangement of shear studs. This means that the direct application of current design guidelines usually produces very conservative results and close arrangement of shear studs precludes pouring concrete within exterior steel faceplates. In this light, an improved guideline to determine the stud spacing should be introduced, and this paper proposes an improved ratio of the stud spacing to the thickness of steel plate on the basis of numerous parametric studies to evaluate the relative influence of the stud spacing on the stability of the SCP.

Key Words
steel-concrete plate composite; shear stud spacing; local buckling; design guideline

Address
Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea.



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