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CONTENTS
Volume 69, Number 6, March25 2019
 

Abstract
Investigations on seismic performance of eccentrically braced frames equipped with dual vertical links have received little attention. Therefore, the main goal of this paper is to describe design steps for such frames and evaluate nonlinear performance of this system according to the reliability analysis. In this study, four and eight story frame structures are analyzed and the response modification factors for different intensity and damage levels are derived in a matrix form based on a new approach. According to the obtained results, the system has high ductility and acceptable seismic performance. Moreover, it is concluded that using response modification factor equal to 8 in the design of system provides desirable seismic reliability under the design and maximum probable hazard levels. Due to desirable performance and significant advantages of the dual vertical links, this system can be used as a main lateral load bearing system, in addition to its application for rehabilitation of damaged structures.

Key Words
eccentric bracing; dual vertical link; demand response modification factor; capacity response modification factor; reliability analysis; fragility curves

Address
Vahid Mohsenian and Ali Nikkhoo: Department of Civil Engineering, University of Science and Culture, Tehran, Iran

Abstract
The present investigation has focus on the study of deformation due to thermomechanical sources in a thick circular plate. The thick circular plate is homogeneous, transversely isotropic with two temperatures and without energy dissipation. The upper and lower surfaces of the thick circular plate are traction free. The Laplace and Hankel transform has been used for finding the general solution to the field equations. The analytical expressions of stresses, conductive temperature and displacement components are computed in the transformed domain. However, the resulting quantities are obtained in the physical domain by using numerical inversion technique. Numerically simulated results are illustrated graphically. The effects of two temperatures by considering different values of temperature parameters are shown on the various components. Some particular cases are also figured out from the present investigation.

Key Words
Laplace and Hankel transform; two temperature; thermoelastic; thick circular plate; transversely isotropic

Address
Parveen Lata and Iqbal Kaur: Department of Basic and Applied Sciences, Punjabi University, Patiala, Punjab, India

Abstract
The 3-noded metric Timoshenko beam element with an offset of the internal node from the element centre is used here to demonstrate the best-fit paradigm using function space formulation under locking and mesh distortion. The best-fit paradigm follows from the projection theorem describing finite element analysis which shows that the stresses computed by the displacement finite element procedure are the best approximation of the true stresses at an element level as well as global level. In this paper, closed form best-fit solutions are arrived for the 3-noded Timoshenko beam element through function space formulation by combining field consistency requirements and distortion effects for the element modelled in metric Cartesian coordinates. It is demonstrated through projection theorems how lock-free best-fit solutions are arrived even under mesh distortion by using a consistent definition for the shear strain field. It is shown how the field consistency enforced finite element solution differ from the best-fit solution by an extraneous response resulting from an additional spurious force vector. However, it can be observed that when the extraneous forces vanish fortuitously, the field consistent solution coincides with the best-fit strain solution.

Key Words
metric element; function spaces; symmetric formulation; element distortion; best-fit paradigm; variational correctness; orthogonal projections

Address
S. Manju: CSIR-National Aerospace Laboratories, Bangalore 560017, India
Somenath Mukherjee: CSIR-Central Mechanical Engineering Research Institute, Durgapur 713209, India

Abstract
In order to study the axial compression performance of sand-lightweight concrete-filled steel tube (SLCFST) stub columns, three circular SLCFST (C-SLCFST) stub column specimens and three SLCFST square (S-SLCFST) stub column specimens were fabricated and static monotonic axial compression performance testing was carried out, using the volume ratio between river sand and ceramic sand in sand-lightweight concrete (SLC) as a varying parameter. The stress process and failure mode of the specimens were observed, stress-strain curves were obtained and analysed for the specimens, and the ultimate bearing capacity of SLCFST stub column specimens was calculated based on unified strength theory, limit equilibrium theory and superposition theory. The results show that the outer steel tubes of SLCFST stub columns buckled outward, core SLC was crushed, and the damage to the upper parts of the S-SLCFST stub columns was more serious than for C-SLCFST stub columns. Three stages can be identified in the stress-strain curves of SLCFST stub columns: an elastic stage, an elastic-plastic stage and a plastic stage. It is suggested that AIJ-1997, CECS 159:2004 or AIJ-1997, based on superposition theory, can be used to design the ultimate bearing capacity under axial compression for C-SLCFST and S-SLCFST stub columns; for varying replacement ratios of natural river sand, the calculated stress-strain curves for SLCFST stub columns under axial compression show good fitting to the test measure curves.

Key Words
sand-lightweight concrete-filled steel tube; stub column; cross section form; replacement ratio; ultimate bearing capacity under axial compression; complete curve between stress and strain

Address
Xianggang Zhang, Xinyan Lin, Jianhui Yang and Lei Fu:
1) Henan Province Engineering Laboratory of Eco-Architecture and the Built Environment, Henan Polytechnic University, Jiaozuo, Henan, China
2) School of Civil Engineering, Henan Polytechnic University, Jiaozuo, Henan, China
Dapeng Deng: School of Civil Engineering, Henan Polytechnic University, Jiaozuo, Henan, China

Abstract
In the current research paper, a quasi-3D beam theory is developed for free vibration analysis of functionally graded microbeams. The volume fractions of metal and ceramic are assumed to be distributed through a beam thickness by three functions, power function, symmetric power function and sigmoid law distribution. The modified coupled stress theory is used to incorporate size dependency of micobeam. The equation of motion is derived by using Hamilton\'s principle, however, Navier type solution method is used to obtain frequencies. Numerical results show the effects of the function distribution, power index and material scale parameter on fundamental frequencies of microbeams. This model provides designers with guidance to select the proper distributions and functions.

Key Words
vibration; microbeam; law distribution; quasi-3D theory; functionally graded material

Address
Youcef Tlidji and Kadda Draiche:
1) Laboratory of Materials et Hydrology, University of Sidi Bel Abbes, BP 89 Cite Ben M\'hidi, 22000 Sidi Bel Abbes, Algeria
2) Department of Civil Engineering, Ibn Khaldoun University, BP 78 Zaaroura, 14000 Tiaret, Algeria
Mohamed Zidour:
1) Department of Civil Engineering, Ibn Khaldoun University, BP 78 Zaaroura, 14000 Tiaret, Algeria
2) Laboratory of Geomatics and Sustainable Development, Ibn Khaldoun University of Tiaret, Algeria
Abdelkader Safa and Abdelmoumen Anis Bousahla:
1) Laboratory of Materials et Hydrology, University of Sidi Bel Abbes, BP 89 Cite Ben M\'hidi, 22000 Sidi Bel Abbes, Algeria
2) Department of Civil Engineering, Ahmed Zabana University, 48000 Relizane, Algeria
Mohamed Bourada: Laboratory of Materials et Hydrology, University of Sidi Bel Abbes, BP 89 Cite Ben M\'hidi, 22000 Sidi Bel Abbes, Algeria
Abdelouahed Tounsi:
1) Laboratory of Materials et Hydrology, University of Sidi Bel Abbes, BP 89 Cite Ben M\'hidi, 22000 Sidi Bel Abbes, Algeria
2) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia
S.R. Mahmoud: Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia

Abstract
Past earthquakes have shown that appropriately designed and detailed buildings with shear walls have great performance such a way that a considerable portion of inelastic energy dissipation occurs in these structural elements. A plastic hinge is fundamentally an energy diminishing means which decrease seismic input energy through the inelastic deformation. Plastic hinge development in a RC shear wall in the areas which have plastic behavior depends on the ground motions characteristics as well as shear wall details. One of the most generally used forms of structural walls is flanged RC wall. Because of the flanges, these types of shear walls have large in-plane and out-of-plane stiffness and develop high shear stresses. Hence, the purpose of this paper is to evaluate the main characteristics of these structural components and provide a more comprehensive expression of plastic hinge length in the application of performance-based seismic design method and promote the development of seismic design codes for shear walls. In this regard, the effects of axial load level, wall height, wall web and flange length, as well as various features of earthquakes, are examined numerically by finite element methods and the outcomes are compared with consistent experimental data. Based on the results, a new expression is developed which can be utilized to determine the length of plastic hinge area in the flanged RC shear walls.

Key Words
plastic hinge; flanged shear wall; time history analysis; RC element

Address
Farzad Ghaderi Bafti and Alireza Mortezaei: Civil Engineering Department, Seismic Geotechnical and High Performance Concrete Research Centre, Semnan Branch, Islamic Azad University, Semnan, Iran
Ali Kheyroddin: Civil Engineering Faculty, Semnan University, Semnan, Iran

Abstract
Minimizing the stress concentration around hypotrochoid hole in finite metallic plates under in-plane loading is an important consideration in engineering design. In the analysis of finite metallic plate, the effective factors on stress distribution around holes include curvature radius of the corner of the hole, hole orientation, plate\'s aspect ratio, and hole size. This paper aims to investigate the impact of these factors on stress analysis of finite metallic plate with central hypotrochoid hole. To obtain the lowest value of stress around a hypotrochoid hole, a swarm intelligence optimization method named ant lion optimizer is used. In this study, with the hypothesis of plane stress circumstances, analytical solution of Muskhelishvili\'s complex variable method and conformal mapping is employed. The plate is taken into account to be finite, isotropic and linearly elastic. By applying suitable boundary conditions and least square boundary collocation technique, undefined coefficients of stress function are found. The results revealed that by choosing the above-mentioned factor correctly, the lowest value of stress would be obtained around the hole allowing to an increment in load-bearing capacity of the structure.

Key Words
finite metallic plates; stress concentration factor; hypotrochoid hole; analytical solution; ant lion optimizer

Address
Mohammad H. Bayati Chaleshtari and Mohammad Jafari: Faculty of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, Iran

Abstract
In recent years, interest is growing in the engineering community on the experimental assessment and the theoretical prediction of the out-of-plane (OOP) seismic response of unreinforced masonry (URM) infills, which are widespread in Reinforced Concrete (RC) buildings in Europe and in the Mediterranean area. In the literature, some mechanical-based models for the prediction of the entire OOP force-displacement response have been formulated and proposed. However, the small number of experimental tests currently available has not allowed, up to current times, a robust and reliable evaluation of the predictive capacity of such response models. To enrich the currently available experimental database, six pure OOP tests on URM infills in RC frames were carried out at the Department of Structures for Engineering and Architecture of the University of Naples Federico II. Test specimens were built with the same materials and were different only for the thickness of the infill walls and for the number of their edges mortared to the confining elements of the RC frames. In this paper, the results of these experimental tests are briefly recalled. The main aim of this study is comparing the experimental response of test specimens with the prediction of mechanical models presented in the literature, in order to assess their effectiveness and contribute to the definition of a robust and reliable model for the evaluation of the OOP seismic response of URM infill walls.

Key Words
URM infill wall; experimental; mechanical; out-of-plane strength; out-of-plane response; arching action; stripe method

Address
Gerardo M. Verderame, Paolo Ricci and Mariano Di Domenico: Department of Structures for Engineering and Architecture, University of Naples Federico II Via Claudio 21 – 80125 – Naples, Italy

Abstract
In this study, the problem of axisymmetric deformation of prestressed Föppl-Hencky membrane under constrained deflecting was analytically solved and its closed-form solution was presented. The small-rotation-angle assumption usually adopted in membrane problems was given up, and the initial stress in membrane was taken into account. Consequently, this closed-form solution has higher calculation accuracy and can be applied for a wider range in comparison with the existing approximate solution. The presented numerical examples demonstrate the validity of the closed-form solution, and show the errors of the contact radius, profile and radial stress of membrane in the existing approximate solution brought by the small-rotation-angle assumption. Moreover, the influence of the initial stress on the contact radius is also discussed based on the numerical examples.

Key Words
circular membrane; axisymmetric deformation; constrained deflecting; uniformly loading; closed-form solution

Address
Yong-Sheng Lian, Jiao Dong and Zhi-Xin Yang: School of Civil Engineering, Chongqing University, Chongqing 400045, PR China
Jun-Yi Sun and Zhou-Lian Zheng:
1) School of Civil Engineering, Chongqing University, Chongqing 400045, PR China
2) Key Laboratory of New Technology for Construction of Cities in Mountain Area (Chongqing University),
Ministry of Education, Chongqing 400045, PR China

Abstract
A cable-stayed bridge (CSB) is one of the most complicated structures, especially when subjected to earthquakes and taking into consideration the effect of soil-structure-interaction (SSI). A CSB of a 500 m mid-span was modeled by the SAP2000 software and was subjected to four different earthquakes. To mitigate the harmful effect of the vibration generated from each earthquake, four mitigation schemes were used and compared with the non-mitigation model to determine the effectiveness of each scheme, when applying on the SSI or fixed CSB models. For earthquake mitigation, tuned mass damper (TMD) systems and spring dampers with different placements were used to help reduce the seismic response of the CBS model. The pylons, the mid-span of the deck and the pylon-deck connections are the best TMDs and spring dampers placements to achieve an effective reduction of the earthquake response on such bridges.

Key Words
cable-stayed bridge; soil-structure-interaction (SSI); tuned mass damper (TMD); spring damper; seismic response; nonlinear analysis

Address
Denise-Penelope N. Kontoni: Department of Civil Engineering, Technological Educational Institute of Western Greece, 1 M. Alexandrou Str., Koukouli, GR-26334 Patras, Greece
Ahmed Abdelraheem Farghaly: Department of Civil and Architectural Constructions, Faculty of Industrial Education, Sohag University, Sohag 82524, Egypt


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