Seismic vulnerability and protection of nonstructural components

An area of earthquake disaster mitigation research of growing interest in U.S. is one of assessing seismic vulnerability and developing mitigation measures for nonstructural components in buildings, particularly critical facilities. This area of research has had limited international collaboration, but has strong potential for broader international involvement. The research activities in the U.S. in the area of nonstructural components has the broad objective of developing knowledge, assessment tools, analysis and design procedures, fragility data, and protective measures. These activities are designed, in part, to contribute to efforts underway to prepare guidelines for perfomance-based earthquake engineering and reduce economic losses in future earthquakes. Reported in this presentation are some completed and current work in the nonstructural components area. They address two important technical issues associated with their seismic perfomance: seismic vulnerability and protection strategies

Sliding fragility of unrestrained equipment in critical facilities

Through the years, seismic design of buildings has been well developed and is continually updated and improved. Yet, nonstructural components housed in buildings are rarely designed with the same degree of consideration as buildings. As a result, buildings that remain structurally sound after a strong earthquake often lose their operational capabilities due to damage to their nonstructural components, such as piping systems, communication equipment and other types of components. The recent 1994 Nothridge, 1995 Kobe and 1999 Turkey and Taiwan earthquakes further demonstrate the importance of controlling damage to nonstructural components, particularly in critical facilities, such as hospitals, in order to ensure their funcionality during and after a major earthquake. Earthquake vulnerability of nonstructural components is usually reduced by fastening or bracing individual objects. However, there are some nonstructural components in buildings which often cannot be restrained for protection from earthquake shaking. The response of these objects will consist of sliding, rocking or jumping. Understanding these response types will allow estimation of vulnerability to earthquake damage and will assist in the design of appropiate mitigation measures. This research concentrates on experimental and analytical studies of the sliding response of freestanding rigid objects subjected to base excitation. Analytical and experimental techniques are combined to allow determination of fragility curves for free-standing rigid equipment under seismic excitations for further improvement of seismic mitigation measures. A discrete system model, an analytical model for two-dimensional sliding under two-dimensional excitation, is developed and analyzed for specific base motions. Shaking table testing with a range of excitations and systems parameters is used to define stability bounds for pure sliding motion. A comparison of the analytical and experimental results is then performed to further verify the validity of the analytical model. Discrepancies in the model assumptions and future improvements of the nonstructural model are also discussed in this report (AU)

Nonstructural damage database

This report describes a database which provides damage information for nonstructural components in buildings and other constructed facilities. It contains nearly 3.000 entries encompassing more than 50 earthquakes from the 1964 Alaska earthquake to the present. Information from various publications, including books, reports and periodicals, was gathered and recorded, including a description of the damage occurred, and strong ground motion records, when availabe. The database is a work in progress, and will continue to be updated asnew information becomes available

Experimental verification of acceleration feedback control strategies for an active tendon system

Most of the current active structural control strategies for aseismic protection have been based on either full - state feedback (i.e.,structural displacements and velocities) or velocity feedback. However, accurate measurement of the displacements and velocities is difficult to achieve directly, particularly during seismic activity, since the foundation of the structure is moving with the ground. Because accelerometers can readily provide reliable and inexpensive measurements of the structural accelerations at strategic points on the structure, development of control methods based on acceleration feedback is an ideal solution to this problem. The purpose of this report is to demostrate experimentally that stochastic control methods based on absolute acceleration measurements are viable and robust, and that they can achieve perfomance levels comparable to full - state feedback controllers (AU)

Effect of random airway sizes on aerosol deposition.

A previously developed deposition model is used to determine the total and regional deposition of inhaled aerosols in a population of human lungs by taking into account variability in airway dimensions. The results for particle sizes ranging from 0.1 micron to 8 micron aerodynamic diameter agree favorably with experimental data, thus suggesting that observed intersubject deposition variability is caused primarily by difference in airway dimensions.

A statistical description of the human tracheobronchial tree geometry.

Most physiological studies which made use of lung geometry have utilized average deterministic models of the tracheobronchial tree geometry, such as Weibel's Model A (1963). However, as shown by morphometric studies, it is well known that there are significant inter-subject and intra-subject variabilities in the structural components of the human lung. Hence, inherent inaccuracies exist when deterministic dimensions for lung geometry are used. In this paper, a statistical description of the lung geometry is presented. Using Weibel's Model A as the underlying average model, probability distributions for the lengths and the diameters of airways and for the number and volume of alveoli are proposed based on morphometric data. As a check for consistency, the probability distribution of the functional residual capacity is derived from those associated with airways and alveoli and it is compared with reported data. Results of this comparison are favorable, suggesting that the statistical description presented herein represents a self-consistent model for lung geometry which can be used for studies of problems related to pulmonary physiology.