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


sss
 
CONTENTS
Volume 2, Number 4, October 2006
 

Abstract
The paper considers the dynamic behaviour of the two-layered and multi-layered plate packets under dynamic (seismic) loading. These models correspond to the base-foundation packet structures. The analysis of the various models, including the models of contact between the layers, is derived on the base of the precise solutions of elasticity theory equations. It is shown that the application of the seismoisolator or, in general, less rigid materials between the base and the foundation brings to reduction of the natural frequencies of free vibrations of the packet base-foundation, as well as to the significant reduction of the negative seismic effect on the structures.

Key Words
free vibrations; seismoisolator; frequencies; layered plates.

Address
Department of Plates and Shells, Institute of Mechanics, National Academy of Sciences, Yerevan, Armenia

Abstract
In the case of hospital buildings, where seismic design requirements are very high, existing structures and especially those attacked by past earthquakes, appear, often, unable to fulfil the necessary safety prerequisites. In this paper, the retrofitting of hospital buildings is investigated, using alternative methods of repair and strengthening. Analysis of an existing hospital building in Patras, Greece, is performed. The load-bearing system is a reinforced concrete system. Two solutions are proposed: strengthening using concrete jackets around column and beam elements and application of viscoelastic dampers for the increase of the stability of the structure. Adequate finite element models are constructed for each case and conclusions are drawn on the efficiency of each rehabilitation method.

Key Words
earthquake; hospital; passive control; dampers; rehabilitation; retrofitting; finite element analsis; jackets.

Address
Institute of Structural Analysis and Aseismic Research, School of Civil Engineering, National Technical University of Athens, 9, Iroon Polytechniou, Zografou Campus, 15773, Athens, Greece

Abstract
The reliability analysis of structures subjected to stochastic loading involves evaluation of time and probability of the system

Key Words
first-passage time problem; reliability; large deviations analysis.

Address
Space Research Institute, Russian Academy of Sciences, Moscow 117997, Russia

Abstract
The paper describes the testing facilities and the methodology on testing of laminated rubber bearings envisaged for application in the system of Dynamic Damper (DD) of seismic isolated buildings, as well as the obtained results. For the first time in Armenia laminated rubber bearings were tested simultaneously under the action of horizontal shear force and vertical tension force. The test results have proven the possibility of using rubber bearings as elements subjected to tension due to action of the mass of DD. Also it was confirmed that the suggested structural concept of DD for reducing the displacements and shear forces of seismic isolation systems will have reliable behavior during the design level earthquakes.

Key Words
seismic isolation; dynamic damper; testing; rubber bearing; shear; tension; modulus; stiffness; displacement.

Address
Engineering Research Center, The American University of Armenia, 40 Marshal Baghramian st., 375019, Yerevan, Armenia

Abstract
This paper illustrates an analytical investigation of the vibration parameters of buildings on sliding seismic isolation bearings with elastic limiters of the relative displacement. The installation scheme of sliding bearings and elastic limiters for the separate unit of a 4 storey hospital building with brick walls is designed. The analysis of the vibrations of the hospital building is conducted for harmonic base excitation.

Key Words
earthquake; building; foundation; seismic isolation bearings; rubber limiter; horizontal oscillations; accelerations; dynamic response.

Address
Kyrgyz State University of Construction, Transportation and Architecture, House 1/ Apartment 1, Jilgorodok Sovmina, 720016, Bishkek, Kyrgystan

Abstract
A procedure to retrofit existing essential facilities subjected to seismic excitation is proposed. The main features of this procedure are to reduce maximum acceleration and associated forces in buildings subjected to seismic excitation by reducing their strength (weakening). The weakening retrofit, which is an opposite strategy to strengthening, is particularly suitable for buildings having overstressed components and foundation supports or having weak brittle components. However, by weakening the structure large deformations are expected. Supplemental damping devices however can control the deformations within desirable limits. The structure retrofitted with this strategy will have, therefore, a reduction in the acceleration response and a reduction in the deformations, depending on the amount of additional damping introduced in the structure. An illustration of the above strategy is presented here through an evaluation of the inelastic response of the structure through a nonlinear dynamic analysis. The results are compared with different retrofit techniques. A parametric analysis has also been carried out to evaluate the effectiveness of the retrofitting method using different combination of the performance thresholds in accelerations and displacements through fragility analysis.

Key Words
damping; fragility; inelastic spectral analysis; retrofit; strengthening; weakening.

Address
Stefania Viti; Department of Constructions, University of Florence, Italy
Gian Paolo Cimellaro and Andrei M. Reinhorn; Department of Civil, Structural & Environmental Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA

Abstract
Equations describing deformation defects, damage accumulation, and fracture condition have been suggested. Analytical and numerical solutions have been obtained for defects produced by a shear in a fixed direction. Under cyclic loading the number of cycles to failure well fits the empirical Koffin-Manson law. The developed model is expanded to the case of the micro-plastic deformation, which accompanies martensite accommodation in shape memory alloys. Damage of a shape memory specimen has been calculated for two regimes of loading: a constant stress and cyclic variation of temperature across the interval of martensitic transformations, and at a constant temperature corresponding to the pseudoelastic state and cyclic variation of stress. The obtained results are in a good qualitative agreement with available experimental data.

Key Words
shape memory alloys; modeling; fracture; cyclic loading, thermocycling.

Address
Research Institute of Mathematics and Mechanics, Saint-Petersburg State University, Universitetski pr., 28, Stary Petergof, 198504, St-Petersburg, Russia


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