Techno Press
Tp_Editing System.E (TES.E)
Login Search


sem
 
CONTENTS
Volume 54, Number 1, April10 2015
 

Abstract
An experimental investigation is conducted to examine the behavior and cracking of steel fiberreinforced concrete spandrel L-shaped beams subjected to combined torsion, bending, and shear. The experimental program includes 12 medium-sized L-shaped spandrel beams organized into two groups, namely, specimens with longitudinal reinforcing bars, and specimens with bars and stirrups. All cases are examined with 0%, 1%, and 1.5% steel fiber volume fractions and tested under two different loading eccentricities. Test results indicate that the torque to shear ratio has a significant effect on the crack pattern developed in the beams. The strain on concrete surface follows the crack width value, and the addition of steel fibers reduces the strain. Fibrous concrete beams exhibited improved overall torsional performance compared with the corresponding non-fibrous control beams, particularly the beams tested under high eccentricity.

Key Words
reinforced concrete; torsion; combined loading; spandrel beam; steel fiber; crack

Address
Omer Farouk Ibraheem, B.H. Abu Bakar and I. Johari: Department of Civil Engineering, University Sains Malaysia (USM), Penang, Malaysia

Abstract
Open ground storey (OGS) buildings are characterized by the sudden reduction of stiffness in the ground storey with respect to the upper infilled storeys. During earthquakes, this vertical irregularity may result in accumulated damage in the ground storey members of OGS buildings without much damage in the upper storeys. Hence, the structural design of OGS buildings needs special attention. The present study suggests a modification of existing displacement-based design (DBD) procedure by proposing a new lateral load distribution. The increased demands of ground storey members of OGS buildings are estimated based on non-linear time history analysis results of four sets of bare and OGS frames having four to ten storey heights. The relationship between the increased demand and the relative stiffness of ground storey (with respect to upper storeys) is taken as the criterion for developing the expression for the design lateral load. It is also observed that under far-field earthquakes, there is a decrease in the ground storey drift of OGS frames as the height of the frame increases, whereas there is no such reduction when these frames are subjected to near-field earthquakes.

Key Words
open ground storey buildings; pilotis; displacement-based design; stiffness irregularity; time history analysis; storey drift; base shear

Address
Jiji Anna Varughese: Government Engineering College, Barton Hill, Thiruvananthapuram, Kerala, 695 035, India
Devdas Menon and A. Meher Prasad: Indian Institute of Technology, Madras, Chennai, 600 036, India

Abstract
The performance of a newly generated steel connection known as SidePlateTM moment connection for seismic loading and progressive collapse phenomenon has been investigated in this paper. The seismic evaluation portion of the study included a thorough study on of interstory drift angles and flexural strengths based on 2010 AISC Seismic Provisions while the acceptance criteria provided in UFC 4- 023-03 guideline to resist progressive collapse must be satisfied by the rotational capacity of the connections. The results showed that the SidePlate moment connection was capable of attaining adequate rotational capacity and developing full inelastic capacity of the connecting beam. Moreover, the proposed connection demonstrated an exceptional performance for keeping away the plastic hinges from the connection and exceeding interstory drift angle of 0.06 rad with no fracture developments in beam flange groove-welded joints. The test results indicated that this type of connection had strength, stiffness and ductility to be categorized as a rigid, full-strength and ductile connection.

Key Words
sideplate moment connection; interstory drift angle; progressive collapse; seismic performance

Address
Iman Faridmehr, Mohd Hanim Osman, Mahmood Bin Md. Tahir: UTM-Construction Research Centre, Faculty of Civil Engineering, Universiti Teknologi Malaysia, Skudai, Johor, 81310, Malaysia
Ali Farokhi Nejad: Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Skudai, Johor, 81310, Malaysia
Reza Hodjati: Department of Civil Engineering, Shahrood Branch, Islamic Azad University, Shahrood, Iran

Abstract
Taking the mid-span/center-point of the structure as the reference point of capturing the maximum dynamic response is very customary in the available literature of the moving load problems. In this article, the absolute maximum dynamic response of an Euler-Bernoulli beam subjected to a moving mass is widely investigated for various boundary conditions of the base beam. The response of the beam is obtained by utilizing a robust numerical method so-called OPSEM (Orthonormal Polynomial Series Expansion Method). It is underlined that the absolute maximum dynamic response of the beam does not necessarily take place at the mid-span of the beam and thus the conventional analysis needs modifications. Therefore, a comprehensive parametric survey of the base beam absolute maximum dynamic response is represented in which the contribution of the velocity and weight of the moving inertial objects are scrutinized and compared to the conventional version (maximum at mid-span).

Key Words
absolute maximum dynamic response; Euler-Bernoulli beam; moving mass; OPSEM

Address
Mohammad Ali Lotfollahi-Yaghin and Hassan Jafarian Kafshgarkolaei: Department of Civil Engineering, University of Tabriz, Tabriz, Iran
Hamed Allahyari and Taher Ghazvinic: Department of Civil Engineering, Babol University of Technology, Babol, Iran


Abstract
In this paper, a receding contact problem for an elastic layer resting on two quarter planes is considered. The layer is pressed by a stamp and distributed loads. It is assumed that the contact surfaces are frictionless and only compressive traction can be transmitted through the contact surfaces. In addition the effect of body forces are neglected. Firstly, the problem is solved analytically based on theory of elasticity. In this solution, the problem is reduced into a system of singular integral equations in which contact areas and contact stresses are unknowns using boundary conditions and integral transform techniques. This system is solved numerically using Gauss-Jacobi integral formulation. Secondly, two dimensional finite element analysis of the problem is carried out using ANSYS. The dimensionless quantities for the contact areas and the contact pressures are calculated under various distributed load conditions using both solutions. It is concluded that the position and the magnitude of the distributed load have an important role on the contact area and contact pressure distribution between layer and quarter plane contact surface. The analytic results are verified by comparison with finite element results.

Key Words
receding contact; quarter plane; Gauss-Jacobi; finite element method; ANSYS

Address
Gökhan Adiyaman: Department of Civil Engineering, Karadeniz Technical University, 61080, Trabzon, Turkey
Murat Yaylaci: Department of Civil Engineering, Recep Tayyip Erdoğan Üniversity, 53100, Rize, Turkey
Ahmet Birinci: Department of Civil Engineering, Karadeniz Technical University, 61080, Trabzon, Turkey

Abstract
This paper focuses on an analytical research on the critical buckling load of cylindrical shells with stepwise variable wall thickness under axial compression. An arctan function is established to describe the thickness variation along the axial direction of this kind of cylindrical shells accurately. By using the methods of separation of variables, small parameter perturbation and Fourier series expansion, analytical formulas of the critical buckling load of cylindrical shells with arbitrary axisymmetric thickness variation under axial compression are derived. The analysis is based on the thin shell theory. Analytic results show that the critical buckling load of the uniform shell with constant thickness obtained from this paper is identical with the classical solution. Two important cases of thickness variation pattern are also investigated with these analytical formulas and the results coincide well with those obtained from other authors. The cylindrical shells with stepwise variable wall thickness, which are widely used in actual engineering, are studied by this method and the analytical formulas of critical buckling load under axial compression are obtained. Furthermore, an example is presented to illustrate the effects of each strake

Key Words
cylindrical shells; tanks; stepwise variable wall thickness; axial compression; critical buckling load

Address
H.G. Fan, Z.P. Chen, W.Z. Feng, F. Zhou, X.L. Shen and G.W. Cao: Institute of Process Equipment, Zhejiang University, 38 Zheda Road, Hangzhou, Zhejiang 310027, P.R. China

Abstract
Structural damage detection using modal strain energy (MSE) is one of the most efficient and reliable structural health monitoring techniques. However, some of the existing MSE methods have been validated for special types of structures such as beams or steel truss bridges which demands improving the available methods. The purpose of this study is to improve an efficient modal strain energy method to detect and quantify the damage in complex structures at early stage of formation. In this paper, a modal strain energy method was mathematically developed and then numerically applied to a fixed-end beam and a three-story frame including single and multiple damage scenarios in absence and presence of up to five per cent noise. For each damage scenario, all mode shapes and natural frequencies of intact structures and the first five mode shapes of assumed damaged structures were obtained using STRAND7. The derived mode shapes of each intact and damaged structure at any damage scenario were then separately used in the improved formulation using MATLAB to detect the location and quantify the severity of damage as compared to those obtained from previous method. It was found that the improved method is more accurate, efficient and convergent than its predecessors. The outcomes of this study can be safely and inexpensively used for structural health monitoring to minimize the loss of lives and property by identifying the unforeseen structural damages.

Key Words
modal strain energy; degree-of-freedom (DOF); finite element method (FEM); vibration based damage detection; structural damage

Address
Parviz Moradipour, Tommy H.T. Chan and Chaminda Gallage: School of Civil Engineering & Built Environment, Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4001, Australia

Abstract
The aluminum dome has been widely used in natatorium, oil storage tank, power plant, coal, as well as other industrial buildings and structures. However, few research has focused on the structural behavior and design method of this dome. At present, most designs of aluminum alloy domes have referred to theories and methods of steel spatial structures. However, aluminum domes and steel domes have many differences, such as elasticity moduli, roof structures, and joint rigidities, which make the design and analysis method of steel spatial structures not fully suitable for aluminum alloy dome structures. In this study, a stability analysis method, which can consider structural imperfection, member initial curvature, semi-rigid joint, and skin effect, was presented and used to study the stability behavior of aluminum dome structures. In addition, some meaningful conclusions were obtained, which could be used in future designs and analyses of aluminum domes.

Key Words
aluminum dome; structure type; stability; semi-rigid; skin effect; member initial curvature

Address
Hongbo Liu and Zhihua Chen: State Key Laboratory Of Hydraulic Engineering Simulation And Safety, Tianjin University, Tianjin 300072, China
Shuai Xu and Yidu Bu: School of Civil Engineering, Tianjin University, Tianjin 300072, China

Abstract
The present investigation is concerned with a study effect of magnetic field and nonhomogenous on the elastic stresses in rotating orthotropic infinite circular cylinder. A certain boundary conditions closed form stress fields solutions are obtained for rotating orthotropic cylinder under initial magnetic field with constant thickness for three cases: (1) Solid cylinder, (2) Cylinder with a circular hole at the center, (3) Cylinder mounted on a circular rigid shaft. Analytical expressions for the components of the displacement and stress fields in different cases are obtained. The effect of rotation and magnetic field and non-homogeneity on the displacement and stress fields are studied. Numerical results are illustrated graphically for each case. The effects of rotating and magnetic field and non-homogeneity are discussed.

Key Words
magnetic field; rotation; free vibrations; non-homogeneous; orthotropic cylinder

Address
Nahed S. Hussein: Department of Mathematics, Faculty of Science, Taif University, Saudi Arabia; Department of Mathematics, Faculty of Science, Cairo University, Egypt
F.S. Bayones: Department of Mathematics, Faculty of Science, Taif University, Saudi Arabia
S.R. Mahmoud: Mathematics Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia; Mathematics Department, Faculty of Science, Sohag University, Egypt

Abstract
In the bolted connections, bolt placements are generally described and are generally made in the direction of design effects and in the perpendicular direction to design effects. In these both directions, the reliability of the distance of bolts to the edges of connection plate and the distance of bolts to each other is investigated for high strength steel connections built up with high strength bolts in this study. For this purpose, simple SL (bearing type shear connection) and SLP (bearing type shear connection for body-fit bolts) type steel connections with St 52 grade steel plates with 8 different thicknesses and with 8.8D grade high strength bolts (HV) were constituted and analyzed under H (Dead Loads+Live Loads+Snow Loads+ Roof Loads) and HZ (H Loads+Wind Loads+Earthquake Loads) loadings. Geometric properties, material properties and design actions were taken as random variables. Monte Carlo Simulation method was used to compute failure risk and the first order second moment method was used to determine the reliability indexes of those different distances describing the placement of bolts. Results obtained from computations have been presented in graphics and in a Table. Then, they were compared with some values proposed by some structural codes. Finally, new equations were constituted for minimum and maximum values of distances describing bolt placement by regression analyses performed on those results.

Key Words
reliability analysis; bolted connection; bolt distance; bolt placement; monte carlo simulation

Address
Ertekin Öztekin: Department of Civil Engineering, Gumushane University, Baglarbasi 29100, Gumushane, Turkey

Abstract
This study presents the effects of the spatial variation of ground motions in a hard rock site on the seismic responses of a base-isolated nuclear power plant (BI-NPP). Three structural models were studied for the BI-NPP supported by different number of lead rubber bearing (LRB) base isolators with different base mat dimensions. The seismic responses of the BI-NPP were analyzed and investigated under the uniform and spatial varying excitation of El Centro ground motion. In addition, the rotational degrees of freedom (DOFs) of the base mat nodes were taken to consider the flexural behavior of the base mat on the seismic responses under both uniform and spatial varying excitation. Finally, the seismic response results for all the analysis cases of the BI-NPP were investigated in terms of the vibration periods and mode shapes, lateral displacements, and base shear forces. The analysis results indicate that: (1) considering the flexural behavior of the base mat has a negligible effect on the lateral displacements of base isolators regardless of the number of the isolators or the type of excitation used; (2) considering the spatial variation of ground motions has a substantial influence on the lateral displacements of base isolators and the NPP stick model; (3) the ground motion spatial variation effect is more prominent on lateral displacements than base shear forces, particularly with increasing numbers of base isolators and neglecting flexural behavior of the base mat.

Key Words
base isolation; nuclear power plant; spatial variation; seismic analysis

Address
Mohamed A. Sayed, Sunghyuk Go and Dookie Kim: Department of Civil and Environmental Engineering, Kunsan National University, South Korea
Sung Gook Choc: INNOS TECH Company, Incheon, South Korea

Abstract
We present a torsion analysis of single-bent leaf flexure that is partially restrained, subject to a torsional load. The theoretical equations for the torsional angle are derived using Castigliano\'s theorem. These equations consider the partially restrained warping, and are verified using finite element analysis (FEA). A sensitivity analysis over the length, width, and thickness is performed and verified via FEA. The results show that the errors between the theory result and the FEA result are lower than 6%. This indicates that the proposed theoretical torsional analysis with partially restrained warping is sufficiently accurate.

Key Words
torsion; warping restraint factor; partially restrained warping; leaf flexure; Castigliano

Address
Nghia Huu Nguyen, Byoung-Duk Lim and Dong-Yeon Lee: School of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749, Republic of Korea


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com