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CONTENTS
Volume 53, Number 1, January10 2015
 

Abstract
Due to design codes and regulations and the variety of building plans in Turkey, it is very often seen that band-type windows are left for ventilation and lightening of the basements of buildings which are used for various purposes such as workplaces and storage. Therefore when the necessary support measures cannot be given, short columns are subjected to very high shear forces and so damage occurs. One of the precautions to avoid the damage of short column mechanisms in buildings where band-type windows are in the basement is to strengthen the short columns with fiber reinforced polymer (FRP). In this study, the effect of the FRP retrofitting process of the short columns around band-windowed structures, which are found especially in basement areas, is analyzed in accordance with Turkish Seismic Code 2007 (TSC 2007). Three different models which are bare frame, frame with short columns and retrofitted short columns with FRP, are created and analyzed according to TSC 2007 performance analysis methods to understand the effects of band windows in basements and the effect of FRP retrofitting.

Key Words
performance analysis; short column; reinforced concrete frame; irregular structures; FRP

Address
Ali Koçak: Yildiz Technical University, 34210, Istanbul, Turkey

Abstract
The cross sections of hollow cylindrical tubes ovalise under a pure bending condition, and this reduces their flexural stiffness as their curvatures increase. It is important to accurately evaluate this phenomenon, known as the \"Brazier effect\", to understand the bending behaviour of the systems considered. However, if the tubes are supported by an elastic medium or foundation, the ovalisation displacements of their cross sections may decrease. From this point of view, the purpose of this research is to analytically investigate the bending characteristics of single- and double-walled elastic tubes contacted by an elastic material by considering the Brazier effect. The Brazier moment, which is the maximum moment-carrying capacity of the ovalised cross section, can be calculated by introducing the strain energy per unit length of the tube in terms of the degree of ovalisation for the tube and the curvature. The total strain energy of the double-walled system is the sum of the strain energies of the outer and inner tubes and that of the compliant core. Results are comparatively presented to show the variation in the degree of ovalisation and the Brazier moment for single- and double-walled tubes.

Key Words
elastic tube; pure bending; Brazier effect

Address
Motohiro Sato: Faculty of Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo 060-8628, Japan
Yuta Ishiwata: Graduate School of Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo 060-8628, Japan

Abstract
The rational analytical solutions are presented for functionally graded beams subjected to arbitrary tractions on the upper and lower surfaces. The Young\'s modulus is assumed to vary exponentially along the thickness direction while the Poisson\'s ratio keeps unaltered. Within the framework of symplectic elasticity, zero eigensolutions along with general eigensolutions are investigated to derive the homogeneous solutions of functionally graded beams with no body force and traction-free lateral surfaces. Zero eigensolutions are proved to compose the basic solutions of the Saint-Venant problem, while general eigensolutions which vary exponentially with the axial coordinate have a significant influence on the local behavior. The complete elasticity solutions presented here include homogeneous solutions and particular solutions which satisfy the loading conditions on the lateral surfaces. Numerical examples are considered and compared with established results, illustrating the effects of material inhomogeneity on the localized stress distributions.

Key Words
functionally graded material; symplectic framework; exact solution; eigensolution

Address
Li Zhao and Wei Z. Gan: Ningbo Key Laboratory for Concrete Structure Durability, Ningbo University of Technology, No.89 Cuibai Road, Ningbo, P.R. China

Abstract
In this paper, a model for the evaluation of shear strength of fibre reinforced polymer (FRP)-reinforced concrete beams is given. The survey of literature indicates that the FRP reinforced beams tested with shear span to depth ratio less than or equal to 1.0 is limited. In this study, eight concrete beams reinforced with GFRP rebars without stirrups are cast and tested over shear span to depth ratio of 0.5 and 1.75. The concrete compressive strength is varied from 40.6 to 65.3 MPa. The longitudinal reinforcement ratio is varied from 1.16 to 1.75. The experimental shear strength and load-deflection response of the beams are determined and reported in this paper. A model is proposed for the prediction of shear strength of beams reinforced with FRP bars. The proposed model accounts for compressive strength of concrete, modulus of FRP rebar, longitudinal reinforcement ratio, shear span to depth ratio and size effect of beams. The shear strength of FRP reinforced concrete beams predicted using the proposed model is found to be in better agreement with the corresponding test data when compared with the shear strength predicted using the eleven models published in the literature. Design example of FRP reinforced concrete beam is also given in the appendix.

Key Words
shear strength; GFRP; concrete deep beams; shear span to depth ratio; size effect

Address
Job Thomas and S. Ramadass: Division of Civil Engineering, School of Engineering, Cochin University of Science and Technology, Kochi, Kerala, PIN 682022 India

Abstract
This study investigates the feasibility of retrofitting an existing building by connecting the existing building to a new building using connecting dampers. The new building is base-isolated and viscoelastic dampers are assigned as connecting dampers. Scaled models are tested under three different earthquake records using a shaking table. The existing building and the new building are 9 and 8 stories respectively. The existing building model shows more than 3% increase in damping ratio. The maximum dynamic responses and the root mean square responses of the existing building model to earthquakes are substantially reduced by at least 20% and 59% respectively. Further, numerical models are developed by conducting time-history analysis to predict the performance of the proposed seismic mitigation system. The predictions agree well with the test results. Numerical simulations are carried out to optimize the properties of connecting dampers and base isolators. It is demonstrated that more than 50% of the peak responses can be reduced by properly adjusting the properties of connecting dampers and base isolators.

Key Words
experimental study, base isolation, connecting damper, adjacent buildings, seismic mitigation

Address
Zhidong Yangand Eddie S.S. Lam: Department of Civil & Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong

Abstract
In case of aircraft impact on nuclear containment structures, the initial kinetic energy of the aircraft is transferred and absorbed by the outer containment, may causing either complete or partial failure of containment structure. In the present study safety analysis of BWR Mark III type containment has been performed. The total height of containment is 67 m. It has a circular wall with monolithic dome of 21m diameter. Crash analysis has been performed for fighter jet Phantom F4. A normal hit at the crown of containment dome has been considered. Numerical simulations have been carried out using finite element code ABAQUS/Explicit. Concrete Damage Plasticity model have been incorporated to simulate the behaviour of concrete at high strain rate, while Johnson-Cook elasto-visco model of ductile metals have been used for steel reinforcement. Maximum deformation in the containment building has reported as 33.35 mm against crash of Phantom F4. Deformations in concrete and reinforcements have been localised to the impact region. Moreover, no significant global damage has been observed in structure. It may be concluded from the present study that at higher velocity of aircraft perforation of the structure may happen.

Key Words
nuclear safety; containment buildings; aircrafts crash; Phantom f4

Address
M.R. Sadique, M.A. Iqbal and P. Bhargava: Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee-247667, India

Abstract
In current bridge management systems (BMSs), load and speed restrictions are applied on unhealthy bridges to keep the structure safe and serviceable for as long as possible. But the question is, whether applying these restrictions will always decrease the internal forces in critical components of the bridge and enhance the safety of the unhealthy bridges. To find the answer, this paper for the first time in literature, looks into the design aspects through studying the changes in demand by capacity ratios of the critical components of a bridge under the train loads. For this purpose, a structural model of a simply supported bridge, whose dynamic behaviour is similar to a group of real railway bridges, is developed. Demand by capacity ratios of the critical components of the bridge are calculated, to identify their sensitivity to increase of speed and magnitude of live load. The outcomes of this study are very significant as they show that, on the contrary to what is expected, by applying restriction on speed, the demand by capacity ratio of components may increase and make the bridge unsafe for carrying live load. Suggestions are made to solve the problem.

Key Words
rating bridges; train loads; axle spacing; criticality; speed restriction; bridge management

Address
Mehran Aflatooni, Tommy H.T. Chan and David P. Thambiratnam: School of Civil Engineering and Built Environment, Science and Engineering Faculty, Queensland University of Technology, 2 George St., Brisbane, Queensland 4001, Australia

Abstract
In this paper, the classical continuum mechanics is adopted and modified to be consistent with the unique behavior of micro/nano solids. At first, some kinematical principles are discussed to illustrate the effect of the discrete nature of the microstructure of micro/nano solids. The fundamental equations and relations of the modified couple stress theory are derived to illustrate the microstructural effects on nanostructures. Moreover, the effect of the material surface energy is incorporated into the modified continuum theory. Due to the reduced coordination of the surface atoms a residual stress field, namely surface pre-tension, is generated in the bulk structure of the continuum. The essential kinematical and kinetically relations of nano-continuums are derived and discussed. These essential relations are used to derive a size-dependent model for Mindlin functionally graded (FG) nano-plates. An analytical solution is derived to show the feasibility of the proposed size-dependent model. A parametric study is provided to express the effect of surface parameters and the effect of the microstructure couple stress on the bending behavior of a simply supported FG nano plate.

Key Words
couple stress theory; nanomechanics; nano plates; functionally graded materials; surface elasticity; size-dependent model

Address
F.F. Mahmoud and M. Shaat: Mechanical Engineering Department, Zagazig University, Zagazig 44511, Egypt

Abstract
In the present paper a three-dimensional non-linear truss element and a short computer program for the modeling and predicting approximate lateral deflections in thin glass plates by the method of incremental loading are proposed. Due to the out-of-plane large deflections of thin glass plates compared to the plate thickness within each loading increment, the equilibrium and stiffness conditions are written with respect to the deformed structure. An application is presented on a thin fully tempered monolithic rectangular glass plate, laterally supported around its perimeter subjected to uniform wind pressure. The results of the analysis are compared with published experimental results and found to have satisfactory approximation. It is also observed that the large deflections of a glass plate lead to a part substitution of the bending plate behavior by a tensioned membrane behavior which is favorable.

Key Words
truss model; glass plate; tempered glass; geometric nonlinearity; wind pressure; computer program

Address
H. Xenidis: Department of Civil Engineering, Aristotle University of Thessaloniki, 54124, Greece
K. Morfidis: Institute of Engineering Seismology and Earthquake Engineering (EPPO-ITSAK), Thessaloniki 55535, Greece
P.G. Papadopoulos: Department of Civil Engineering, Aristotle University of Thessaloniki, 54124, Greece

Abstract
Elements used in steel structures may be considered as an assembly of number of thin flat walls. Local buckling of these members can limit the buckling capacity of axial load resistance or flexural strength. We can avoid a premature failure, caused by effects of local buckling, by limiting the value of the wall slenderness which depend on its critical buckling stress. According to Eurocode 3, the buckling stress is calculated for an internal wall assuming that the latter is a simply supported plate on its contour. This assumption considers, without further requirement, that the two orthogonal walls to this wall are sufficiently rigid to constitute fixed supports to it. In this paper, we focus on webs of steel profiles that are internal walls delimited by flanges profiles. The objective is to determine, for a given web, flanges dimensions from which the latter can be considered as simple support for this web.

Key Words
local buckling; thin plates; elastic supports

Address
Chems eddine Taleb, Fatiha Ammari and Redouane Adman: Faculty of Civil Engineering, University of Sciences and Technology HOUARI BOUMEDIENE, BP 32 EL ALIA 16111 BAB EZZOUAR Algiers, Algeria

Abstract
This paper is concerned with effects of the wall flexibility on the seismic behavior of groundsupported cylindrical silos. It is a well-known fact that almost all analytical approximations in the literature to determine the dynamic pressure stemming from the bulk material assume silo structure as rigid. However, it is expected that the horizontal dynamic material pressures can be modified due to varying horizontal extensional stiffness of the bulk material which depends on the wall stiffness. In this study, finite element analyses were performed for six different slenderness ratios according to both rigid and flexible wall approximations. A three dimensional numerical model, taking into account bulk material-silo wall interaction, constituted by ANSYS commercial program was used. The findings obtained from the numerical analyses were discussed comparatively for rigid and flexible wall approximations in terms of the dynamic material pressure, equivalent base shear and bending moment. The numerical results clearly show that the wall flexibility may significantly affects the characteristics behavior of the reinforced concrete (RC) cylindrical silos and magnitudes of the responses under strong ground motions.

Key Words
cylindrical silos; wall flexibility; bulk material-silo wall interaction; seismic response

Address
Ramazan Livaoglu: Department of Civil Engineering, Uludağ University, 16059 Bursa, Turkey
Aysegul Durmus: Department of Civil Engineering, Karadeniz Technical University, 61080 Trabzon, Turkey

Abstract
Several structural calamities in the second half of the 20th century have shown that adequate collapse-resistance cannot be achieved by designing the individual elements of a structure without taking their interconnectivity into consideration. It has long been acknowledged that membrane behaviour of reinforced concrete structures can significantly increase the robustness of a structure and delay a complete collapse. An experimental large-scale test was conducted on a horizontally restrained, continuous reinforced concrete slab exposed to an artificial failure of the central support and subsequent loading until collapse of the specimen. Within this investigation the development of catenary action associated with the formation of large displacements was observed to increase the ultimate load capacity of the specimen significantly. The development of displacements, strains and horizontal forces within this investigation confirmed a load transfer process from an elastic bending mechanism to a tension controlled catenary mechanism. In this contribution a special focus is directed towards strain and crack development at critical sections. The results of this contribution are of particular importance when validating numerical models related to the development of catenary action in concrete slabs.

Key Words
concrete; slabs; robustness; membrane actions; real-scale testing

Address
Dirk Gouverneur, Robby Caspeeleand Luc Taerwe: Department of Structural Engineering, Ghent University, Technologiepark-Zwijnaarde 904, 9052 Ghent, Belgium


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