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CONTENTS
Volume 71, Number 2, July25 2019
 

Abstract
This paper presents the numerical simulation of membrane structure under impact load. Firstly, the numerical simulation model is validated by comparing with the test in Hao\'s research. Then, the effects of the shape of the projectile, the membrane prestress and the initial impact speed, are investigated for studying the dynamic response and failure mechanism, based on the membrane displacement, projectile acceleration and kinetic energy. Finally, the results show that the initial speed and the punch shape are related with the loss of kinetic energy of projectiles. Meanwhile, the membrane prestress is an important factor that affects the energy dissipation capacity and the impact resistance of membrane structures.

Key Words
tensile membrane structures; failure mechanism; dynamic response; impact load; parameter analysis

Address
Yingying Zhang, Yushuai Zhao, Mingyue Zhang: Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Engineering, State Key Laboratory for Geomechanics & Deep Underground Engineering, Jiangsu Collaborative Innovation Center for Building Energy Saving and Construction Technology
Yi Zhou: School of Civil Engineering, Southwest Jiaotong University
Qilin Zhang: College of Civil Engineering, Tongji University

Abstract
Optimum shape and length of laterally loaded piles can be obtained with different optimization techniques. In particular, the Fully Stress Design method (FSD) is an optimality condition that allows to obtain the optimum shape of the pile, while the optimum length can be obtained through a transversality condition at the pile lower end. Using this technique, the structure is analysed by finite elements and shaped through the FSD method by contemporarily checking that the transversality condition is satisfied. In this paper it is noted that laterally loaded piles with optimum shape and length have some peculiar characteristics, depending on the type of cross-section, that allow to design them with simple calculations without using finite element analysis. Some examples illustrating the proposed simplified design method of laterally loaded piles with optimum shape and length are introduced.

Key Words
Winkler\'s soil; FSD method; laterally loaded piles; optimum shape and length; specific constants; simplified design

Address
Luigi Fenu: Department of Civil & Environment Engineering and Architecture, University of Cagliari, Via Marengo 2, 09123 Cagliari, Italy
Bruno Briseghella and Giuseppe Carlo Marano: College of Civil Engineering, Fuzhou University, No. 2 Xue Yuan Road, University Town, Fuzhou 350108 - Fujian, China

Abstract
It is necessary to predict subway induced vibration if a new subway is to be built. To obtain the vibration response reliably, a three-dimensional (3D) FEM model, consisting of the tunnel, the soil, the subway load and the building above, is established in MIDAS GTS NX. For this study, it is a six-story frame structure built above line 3 of Guangzhou metro. The entire modeling process is described in detail, including the simplification of the carriage load and the determination of model parameters. Vibration measurements have been performed on the site of the building and the model is verified with the collected data. The predicted and measured vibration response are used together to assess vibration level due to the subway traffic in the building. The No.1 building can meet work and residence comfort requirement. This study demonstrates the applicability of the numerical train-tunnel-soil-structure model for the serviceability assessment of subway induced vibration and aims to provide practical references for engineering applications.

Key Words
frame structure; subway induced vibration; train-tunnel-soil-structure model; measurement; model parameters; serviceability assessment; one-third octave

Address
Yuhong Ling, Jingxin Gu: Department of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510640, China
T.Y. Yang: Department of Civil Engineering, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
Rui Liu: Architectural Design and Research Institute of SCUT, Guangzhou 510640, China
Yuhong Ling, Rui Liu: State Key Laboratory of Subtropical Building Science, Guangzhou 510640, China
Yeming Huang: Shum Yip Land Company Limited, Shenzhen 518040, China

Abstract
In a project schedule, it is possible to reduce the time required to complete a project by allocating extra resources for critical activities. However, accelerating a project causes additional expense. This issue is addressed by finding optimal set of time-cost alternatives and is known as the time-cost trade-off problem in the literature. The aim of this study is to identify the optimal set of time-cost alternatives using a multiobjective teaching-learning-based optimization (TLBO) algorithm integrated with the non-dominated sorting concept and is applied to successfully optimize the projects ranging from a small to medium large projects. Numerical simulations indicate that the utilized model searches and identifies optimal / near optimal trade-offs between project time and cost in construction engineering and management. Therefore, it is concluded that the developed TLBO-based multiobjective approach offers satisfactorily solutions for time–cost trade-off optimization problems.

Key Words
critical path method (CPM); multi objective optimization; meta-heuristic algorithm; time cost trade-off problem (TCTP); construction management

Address
Mohammad A. Eirgash: Civil Engineering Department, Institute of Natural Sciences, Karadeniz Technical University, 61080 Trabzon, Turkey.
Vedat Toğan: Civil Engineering Department, Engineering Faculty, Karadeniz Technical University, 61080 Trabzon, Turkey.
Tayfun Dede: Civil Engineering Department, Engineering Faculty, Karadeniz Technical University, 61080 Trabzon

Abstract
Longitudinal fracture behavior of non-linear elastic beam configurations is studied in terms of the strain energy release rate. It is assumed that the beams exhibit continuous material inhomogeneity along the width as well as along the height of the cross-section. The Ramberg-Osgood stress-strain relation is used for describing the non-linear mechanical behavior of the inhomogeneous material. A solution to strain energy release rate is derived that holds for inhomogeneous beams of arbitrary cross-section under combination of axial force and bending moments. Besides, the solution may be applied at any law of continuous distribution of the modulus of elasticity in the beam cross-section. The longitudinal crack may be located arbitrary along the beam height. The solution is used to investigate a longitudinal crack in a beam configuration of rectangular cross-section under four-point bending. The crack is located symmetrically with respect to the beam mid-span. It is assumed that the modulus of elasticity varies continuously according a cosine law in the beam cross-section. The longitudinal fracture behavior of the inhomogeneous beam is studied also by applying the J-integral approach for verification of the non-linear solution to the strain energy release rate derived in the present paper. Effects of material inhomogeneity, crack location along the beam height and non-linear mechanical behavior of the material on the longitudinal fracture behavior are evaluated. Thus, the solution derived in the present paper can be used in engineering design of inhomogeneous non-linear elastic structural members to assess the influence of various material and geometrical parameters on longitudinal fracture.

Key Words
inhomogeneous beam; longitudinal fracture; material nonlinearity; strain energy

Address
Department of Technical Mechanics, University of Architecture, Civil Engineering and Geodesy, 1 Chr. Smirnensky blvd., 1046, Sofia, Bulgaria

Abstract
This paper investigates the probability of failure of reinforced concrete beams for limit state of collapse for flexure and shear. The influence of randomness of the variables on the failure probability is also examined. The Indian standard code for plain and reinforced concrete IS456:2000 is used for the design of beams. Probabilistic models are developed for flexure and shear according to IS456:2000. The loads considered acting on the beam are live load and dead load only. Random variables associated with the limit state equation such as grade of concrete, grade of steel, live load and dead load are identified. Probability of failure is evaluated based on the limit state equation using First Order Reliability Method (FORM). Importance of the random variables on the limit state equations are observed and the variables are accordingly reduced. The effect of the reduced parameters is checked on the probability of failure. The results show the role of each parameter on the design of beam. Thus, the Indian standard guidelines for plain and reinforced concrete IS456:2000 is investigated with the probabilistic and risk-based analysis and design for a simple beam. The results obtained are also compared with the literature and accordingly some suggestions are made.

Key Words
flexure; FORM; IS456:2000; probabilistic; reinforced concrete; shear

Address
Department of Applied Mechanics, Visvesvaraya National Institute of Technology, Nagpur - 440010, Maharashtra, India

Abstract
This paper deals with damage detection in a girder bridge using transmissibility functions as input data to Artificial Neural Networks (ANNs). The original contribution in this work is that these two novel methods are combined to detect damage in a bridge. The damage was simulated in a real bridge in Vietnam, i.e. Ca-Non Bridge. Finite Element Method (FEM) of this bridge was used to show the reliability of the proposed technique. The vibration responses at some points of the bridge under a moving truck are simulated and used to calculate the transmissibility functions. These functions are then used as input data to train the ANNs, in which the target is the location and the severity of the damage in the bridge. After training successfully, the network can be used to assess the damage. Although simulated responses data are used in this paper, the practical application of the technique to real bridge data is potentially high.

Key Words
Structural Health Monitoring (SHM); transmissibility; Artificial Neural Networks (ANNs); bridge monitoring; Finite Element Method (FEM)

Address
Duong H. Nguyen: Department of Electrical energy, metals, mechanical constructions and systems,
Faculty of Engineering and Architecture, Ghent University, Belgium
Duong H. Nguyen: National University of Civil Engineering, Hanoi, Vietnam
Thanh T. Bui: University of Transport and Communications, Hanoi, Vietnam
Guido De Roeck: KU Leuven, Department of Civil Engineering, Structural Mechanics, B-3001 Leuven, Belgium
Magd Abdel Wahab: Division of Computational Mechanics, Ton Duc Thang University, Ho Chi Minh City, Viet Nam
Magd Abdel Wahab: Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Viet Nam

Abstract
In this investigation, study of the static and dynamic behaviors of functionally graded beams (FGB) is presented using a hyperbolic shear deformation theory (HySDT). The simply supported FG-beam is resting on the elastic foundation (Winkler-Pasternak types). The properties of the FG-beam vary according to exponential (E-FGB) and power-law (P-FGB) distributions. The governing equations are determined via Hamilton\'s principle and solved by using Navier\'s method. To show the accuracy of this model (HySDT), the current results are compared with those available in the literature. Also, various numerical results are discussed to show the influence of the variation of the volume fraction of the materials, the power index, the slenderness ratio and the effect of Winkler spring constant on the fundamental frequency, center deflection, normal and shear stress of FG-beam.

Key Words
functionally graded beam; bending; stress; natural frequency; shear deformation theory; Winkler-Pasternak foundation parameters

Address
Lynda Amel Chaabane, Sara Zerouati: LGCE, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria.
Fouad Bourada, Mohamed Sekkal, Abdelhak Derras, Abdeldjebbar Tounsi, Abdelouahed Tounsi :Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Fouad Bourada: Département des Sciences et de la Technologie, Centre Universitaire de Tissemsilt, BP 38004 Ben Hamouda, Algérie
Fatima Zohra Zaoui: Laboratoire de Modélisation Numérique et Expérimentale des Phénomènes Mécaniques, Faculté des Sciences et Technologie, Département de Génie Mécanique, Université Abdelhamid Ibn Badis of Mostaganem, 27000, Algeria
Abdelmoumen Anis Bousahla: 5Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria, 6Centre Universitaire Ahmed Zabana de Relizane, Algérie
Abdelouahed Tounsi: Civil and Environmental Engineering Department, King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia

Abstract
Probabilistic buckling behavior of sandwich panel considering random system parameters using a radial basis function (RBF) approach is presented in this paper. The random system properties result in an uncertain response of the sandwich structure. The buckling load of laminated sandwich panel is obtained by employing higher-order-zigzag theory (HOZT) coupled with RBF and probabilistic finite element (FE) model. The in-plane displacement variation of core as well as facesheet is considered to be cubic while transverse displacement is considered to be quadratic within the core and constant in the facesheets. Individual and combined stochasticity in all elemental input parameters (like facesheets thickness, ply-orientation angle, core thickness and properties of material) are considered to know the effect of different degree of stochasticity, ply- orientation angle, boundary conditions, core thickness, number of laminates, and material properties on global response of the structure. In order to achieve the computational efficiency, RBF model is employed as a surrogate to the original finite element model. The stiffness matrix of global response is stored in a single array using skyline technique and simultaneous iteration technique is used to solve the stochastic buckling equations.

Key Words
sandwich panel; probabilistic buckling behavior; radial basis function; random properties; higher order zigzag theory

Address
Mechanical Engineering Department, National Institute of Technology Silchar, India


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