排序方式： 共有28条查询结果，搜索用时 15 毫秒
1.
The effectiveness of seismic isolation in protecting structural and non‐structural elements from damage has been assessed in an extensive programme of shaking‐table tests, carried out on four identical 1/3.3‐scale, two‐dimensional, reinforced concrete (R/C) frames. Four different isolation systems were considered, namely: (i) rubber‐based, (ii) steel‐based, (iii) shape memory alloy (SMA)‐based and (iv) hybrid, i.e. based on both SMA and steel components, isolation systems. This paper presents a comprehensive overview of the main results of the experimental tests on base‐isolated models, whose structural response is described through: (i) maximum base displacements; (ii) maximum interstorey drifts; (iii) maximum storey accelerations and (iv) maximum storey shear forces. The evolution of the fundamental frequency of vibration of the R/C frame during the tests is also described. The beneficial effects of using base isolation resulted in no or slight damage, under strong earthquakes, to both structural and non‐structural members, as well as to the internal content of the building. The comparison with the experimental results obtained in shaking‐table tests on similar fixed‐base models emphasizes these positive aspects. Finally, advantages and drawbacks related to the use of each isolation system are discussed in the paper. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
2.
3.
Donatello Cardone Giuseppe Gesualdi Domenico Nigro 《Bulletin of Earthquake Engineering》2011,9(4):1227-1255
The mechanical properties of elastomers can change significantly due to air temperature variations. In particular, prolonged
exposure to subzero temperatures can result in rubber crystallization, with a considerable increase in the shear stiffness
of the material. As a result, the seismic response of structures with elastomeric isolators can be strongly influenced by
air temperature. Current seismic codes, indeed, require an upper and lower bound analysis, using suitable modification factors,
to account for the changes in the cyclic behavior of elastomeric isolators due to air temperature variations. In this study,
the sensitivity of the cyclic behavior of elastomeric isolators to air temperature variations is investigated based on the
experimental results of an extensive test program on six different elastomeric compounds for seismic isolators, characterized
by a shear modulus ranging from 0.5 to 1.2 MPa at 100% shear strain and 20°C. The cyclic tests have been performed on small-size
specimens, subjected to shear strain amplitudes and frequency of loading typical for elastomeric seismic isolators, at seven
different air temperatures, ranging from 40 to −20°C. The effects of rubber crystallization due to prolonged exposure to low-temperatures
have been also investigated. A finite element model for the evaluation of the temperature contour map inside a full-size elastomeric
isolator exposed to low air temperatures has been also developed. In the paper, the experimental outcomes are compared with
the modification factors provided by the current seismic codes to account for the temperature effects on the mechanical properties
of elastomeric isolators. 相似文献
4.
A performance-based adaptive methodology for the seismic evaluation of multi-span simply supported deck bridges 总被引：1，自引：1，他引：0
Donatello Cardone Giuseppe Perrone Salvatore Sofia 《Bulletin of Earthquake Engineering》2011,9(5):1463-1498
A performance-based adaptive methodology for the seismic assessment of highway bridges is proposed. The proposed methodology
is based on an Inverse (I), Adaptive (A) application of the Capacity Spectrum Method (CSM), with the capacity curve of the
bridge derived through a Displacement-based Adaptive Pushover (DAP) analysis. For this reason, the acronym IACSM is used to
identify the proposed methodology. A number of Performance Levels (PLs), for which the seismic vulnerability and seismic risk
of the bridge shall be evaluated, are identified. Each PL is associated to a number of Damage States (DSs) of the critical
members of the bridge (piers, abutments, joints and bearing devices). The IACSM provides the earthquake intensity level (PGA)
corresponding to the attainment of the selected DSs, using over-damped elastic response spectra as demand curves. The seismic
vulnerability of the bridge is described by means of fragility curves, derived based on the PGA values associated to each
DS. The seismic risk of the bridge is evaluated as convolution integral of the product between the fragility curves and the
seismic hazard curve of the bridge site. In this paper, the key aspects and basic assumptions of the proposed methodology
are presented first. The IACSM is then applied to nine existing simply supported deck bridges, characterized by different
types of piers and bearing devices. Finally, the IACSM predictions are compared with the results of nonlinear response time-history
analysis, carried out using a set of seven ground motions scaled to the expected PGA values. 相似文献
5.
An extensive experimental program of shaking table tests on reduced‐scale structural models was carried out within the activities of the MANSIDE project, for the development of new seismic isolation and energy dissipation devices based on shape memory alloys (SMAs). The aim of the experimental program was to compare the behaviour of structures endowed with innovative SMA‐based devices to the behaviour of conventional structures and of structures endowed with currently used passive control systems. This paper presents a comprehensive overview of the main results of the shaking table tests carried out on the models with and without special braces. Two different types of energy dissipating and re‐centring braces have been considered to enhance the seismic performances of the tested model. They are based on the hysteretic properties of steel elements and on the superelastic properties of SMAs, respectively. The addition of passive control braces in the reinforced concrete frame resulted in significant benefits on the overall seismic behaviour. The seismic intensity producing structural collapse was considerably raised, interstorey drifts and shear forces in columns were drastically reduced. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
6.
7.
A comprehensive parametric study on the inelastic seismic response of seismically isolated RC frame buildings, designed for gravity loads only, is presented. Four building prototypes, with 23 m × 10 m floor plan dimensions and number of storeys ranging from 2 to 8, are considered. All the buildings present internal resistant frames in one direction only, identified as the strong direction of the building. In the orthogonal weak direction, the buildings present outer resistant frames only, with infilled masonry panels. This structural configuration is typical of many existing RC buildings, realized in Italy and other European countries in the 60s and 70s. The parametric study is based on the results of extensive nonlinear response‐time history analyses of 2‐DOF systems, using a set of seven artificial and natural seismic ground motions. In the parametric study, buildings with strength ratio (Fy/W) ranging from 0.03 to 0.15 and post‐yield stiffness ratio ranging from 0% to 6% are examined. Three different types of isolation systems are considered, that is, high damping rubber bearings, lead rubber bearings and friction pendulum bearings. The isolation systems have been designed accepting the occurrence of plastic hinges in the superstructure during the design earthquake. The nonlinear response‐time history analyses results show that structures with seismic isolation experience fewer inelastic cycles compared with fixed‐base structures. As a consequence, although limited plastic deformations can be accepted, the collapse limit state of seismically isolated structures should be based on the lateral capacity of the superstructure without significant reliance on its inherent hysteretic damping or ductility capacity. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
8.
Donatello Cardone 《Bulletin of Earthquake Engineering》2012,10(4):1267-1284
The re-centring capability is identified by the current design codes as a fundamental feature of seismic isolation systems. In this paper, the re-centring capability of seismic isolation systems characterised by a flag-shaped hysteretic cyclic behaviour is investigated through an extensive parametric study of single-degree-of-freedom hysteretic systems subjected to different natural records. A remarkable example of this kind of isolation system derives from the combination of flat steel-PTFE sliding bearings with auxiliary re-centring devices based on the superelastic properties of Shape Memory Alloys. The results of the parametric analyses are processed statistically and regression analysis relations are derived that show the dependence of the residual displacement after the earthquake on the governing parameters of the isolation system. Based on the analysis results, the features of the flag-shaped system that guarantee sufficient re-centring capability are identified. 相似文献
9.
Tropical cyclone wind field forcing for surge models: critical issues and sensitivities 总被引：1，自引：1，他引：0
Several wind fields developed for Hurricane Katrina (2005) in the US Gulf of Mexico (GOM) are applied with the ADCIRC hydrodynamic
model to explore the sensitivity of predictions of coastal surges to wind fields developed by alternative methods. The alternative
model predictions are evaluated against water level measurements provided by gages at two coastal locations. It is found that
all the post-event analyzed wind fields yield a range of predictions of only ±10% of the available peak surge measurements
regardless of whether the wind fields are produced by dynamical boundary layer models, kinematic analysis methods or a blend.
However, the richness of meteorological forcing data in the GOM is not typically matched in other basins affected by tropical
cyclones and errors may be much larger where storm intensity and size parameters are estimated mainly from satellite data.
The attributes and remaining critical deficiencies of current methods for surface wind specification in both data-rich and
data-poor environments are reviewed. 相似文献
10.
V. F. Cardone E. Piedipalumbo C. Tortora 《Monthly notices of the Royal Astronomical Society》2005,358(4):1325-1336
We present a new family of spherically symmetric models for the luminous components of elliptical and spiral galaxies and their dark matter haloes. Our starting point is a general expression for the logarithmic slope α( r ) = d log ρ/d log r from which most of the cuspy models yet available in literature may be derived. We then dedicate our attention to a particular set of models where the logarithmic slope is a power-law function of the radius r investigating in detail their dynamics assuming isotropy in the velocity space. While the basic properties (such as the density profile and the gravitational potential) may be expressed analytically, both the distribution function and the observable quantities (the surface brightness and the line-of-sight velocity dispersion) have to be evaluated numerically. We also consider the extension to anisotropic models, trying two different parametrization. As the model recently proposed by Navarro et al. as the best fit to their sample of numerically simulated haloes belongs to the family we present here, analytical approximations are given for the most useful quantities. 相似文献