Social Vulnerability to Environmental Hazards

Recent advances in nonlinear passive vibration isolators

The author details the reactions of various concretes on steel reinforcement. Although portland cements, slag cements and high alumina cements are all hydraulic binders, each possess special properties which are examined. The discussion of causes and methods of preventing the corrosion of steel reinforcement covers such aspects as galvanised steel reinforcement, effects of concrete composition, corrosion of steel reinforcments in concrete and prestressed reinforcement. It is concluded that the most significant influences on the corrosion of prestressing wire in concrete are: the presence of chloride; the presence of nitrates; the composition of the concrete; the degree of carbonation of the concrete; concrete compaction and, chlorides and sulphates should be used as far as possible when steel is embedded. (TRRL)

Corrosion of steel by concrete

Structural systems often show nonlinear behavior under severe excitations generated by natural hazards. In that condition, the restoring force becomes highly nonlinear showing significant hysteresis. The hereditary nature of this nonlinear restoring force indicates that the force cannot be described as a function of the instantaneous displacement and velocity. Accordingly, many hysteretic restoring force models were developed to include the time dependent nature using a set of differential equations. This survey contains a review of the past, recent developments and implementations of the Bouc-Wen model which is used extensively in modeling the hysteresis phenomenon in the dynamically excited nonlinear structures.

The Hysteresis Bouc-Wen Model, a Survey

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Seismic Design Of Reinforced Concrete And Masonry Buildings

This report presents a comprehensive description of the current state of knowledge on the behavior of hardware used in seismic isolation and in seismic damping systems. Particular emphasis is placed on the description of fundamental behavior under both non-seismic, service-type loading conditions and under high-speed seismic conditions. Specific problems described and addressed in this report include the following: (1) aging of elastomeric and sliding bearings; (2) effect of ambient temperature on the behavior of elastomeric and sliding bearings; (3) prediction and experimental verification of effects of frictional heating on the sliding bearings; (4) prediction and experimental verification of effects of hysteric heating on the lead-rubber bearings; (5) analysis of elastomeric and sliding bearings; (6) design of elastomeric and sliding bearings based on principles of LRFD and ASD; (7) establishment of upper and lower bound values of properties of seismic isolation bearings for use in the analysis and design; and (8) detailed new testing protocols for seismic isolators and dampers. The presented information may represent the basis for the development of contemporary Guide Specifications for Seismic Isolation Design.

Performance of Seismic Isolation Hardware under Service and Seismic Loading

Seismic isolation is a technique that has been used around the world to protect building structures, nonstructural components and content from the damaging effects of earthquake ground shaking. This paper summarizes current practices, describes widely used seismic isolation hardware, chronicles the history and development of modern seismic isolation through shake table testing of isolated buildings, and reviews past efforts to achieve three-dimensional seismic isolation. The review of current practices and past research are synthesized with recent developments from full-scale shake table testing to highlight areas where research is needed to achieve full seismic damage protection of buildings. The emphasis of this paper is on the application of passive seismic isolation for buildings primarily as practiced in the United States, though systems used in other countries will be discussed.

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A Review of Seismic Isolation for Buildings: Historical Development and Research Needs

An experimental study investigating the influence of lateral displacement on the vertical stiffness of elastomeric and lead–rubber seismic isolation bearings is summarized. Two identically constructed low-damping rubber and lead–rubber seismic isolation bearings were subjected to a series of tests with varying levels of combined lateral displacement and axial (compressive) loading to study this relationship. The results of these tests showed the vertical stiffness decreases with increasing lateral displacement for each bearing tested. Additionally, the vertical stiffness data are used to evaluate four formulations for the estimation of the vertical stiffness as a function of the lateral displacement. From this comparison, two formulations, one based on the Koh–Kelly two-spring model and the other on a piecewise linear relationship, showed good agreement with the experimental data over the wide range of lateral displacements considered in this study.

Vertical Stiffness of Elastomeric and Lead–Rubber Seismic Isolation Bearings

Elastomeric and lead-rubber bearings are two commonly used types of seismic isolation devices During seismic events, some of the bearings in an isolation system will be subjected to large axial compressive loads, caused by gravity plus overturning forces, accompanied by simultaneous large lateral displacements However, the critical load capacity of elastomeric bearings has been shown to reduce with increasing lateral displacement The design of isolation systems composed of these types of bearings therefore requires that stability at the maximum displacement be demonstrated The current procedure to assess the stability uses a ratio of areas, referred to as the overlapping area method, to determine the critical load capacity at a given lateral displacement that must be greater than a combination of axial forces imposed on the bearing Although the overlapping area method provides a simple means of calculating the critical load at a given lateral displacement, it lacks a rigorous theoretical basis and ha

Gordon P. Warn

Papers

Performance of Seismic Isolation Hardware under Service and Seismic Loading

A Review of Seismic Isolation for Buildings: Historical Development and Research Needs

Vertical Stiffness of Elastomeric and Lead–Rubber Seismic Isolation Bearings

Stability of Elastomeric and Lead-Rubber Seismic Isolation Bearings

Performance estimates in seismically isolated bridge structures