Evaluation of bridge damage data from the Loma Prieta and Northridge, California earthquakes

This report presents the significant findings from a study of damage to bridges during the 1989 Loma Prieta and the 1994 Northridge, C A earthquakes. In both earthquakes, less than five percent of the bridges that were exposed to ground shaking were damaged. AS experienced in the past earthquakes, bridges with non-monolithic abutment types, discontinuous spans and single column bents performed poorly. High skew contributed to high damage levels. Data on bridge damage were compiled, reviewed and analyzed to correlate observed bridge damage to structural characteristics of bridge, ground motion levels and estimated repair cost. Damage states reported after the earthquakes were investigated and new damage state definitions for concrete bridges were proposed. bridges were grouped by their structural characteristics and correlation studies were perfomed to obtain ground motion-damage relationships and ground motion-repair cost ratio relationships. Logistic regression analysis was used to obtain empirical fragility curves. Currently available fragility curves and damage probability matrices were compared to observed damage data and the empirical relationships developed in this study (AU)

A method for earthquake motion - damage relationships with application to reinforced concrete frames

This study presents a systematic approach for developing motion-damage relationships that does not rely either on heuristics or on empirical data. Instead, the probability of damage is estimated by quantifying the response of structure subjected to a significant ensemble of ground motions with a wide range of parameter variations. The quantification of the structural response also includes the variability in structural parameters. For this purpose, a Monte Carlo simulation approach is used to determine the probabilities of structural damage, and the ensemble of ground motions is generated using an appropriate model for ground motion simulation. The models for ground motion simulation include the stationary Gaussian model with modulating funtions and the autoregressive moving average (ARMA) models. The Latin hypercube technique is used to increase the efficiency of the Monte Carlo simulation.(AU)

Evaluation of bridge damage data from the 1994 Northridge, CA

Data on bridge damage from earthquake is becoming incresingly more available. Such data however, have not been systematically studies with the objective to evaluate damage charactistics and to correlate these to observed or estimated local ground motion. This paper presents the results from a project in which bridge damage data from the 1994 Northridge earthquake are studiesd. Structural characteristics that are highly correlated with the observed damage are identified. Bridge are grouped by these structural characteristics and empirical fragility curves are developed for these groups. Only about two percent of the bridges that were exposed to ground shaking experienced damage and only 6 of these bridges collapsed. The analyses od data on bridge damage showed that concrete structures designed/built with older design standards were more prone to damage under seismic loading. (AU)

Recent lifeline seismic risk studies

This monograph is a collection of four papers presented at the 1990 Annual Civil Enginnering Convention and Exposition in San Francisco, California. The papers summarize seismic loss and reliability analysis methods for complex spatially distributed lifeline systems. The emphasis in all the papers is on methods for direct loss estimation rather than on down time and other indirect losses. The methods include models for the spatial distribution of earthquake ground shaking, inventories, component fragilities, total system loss evaluation and propagation of uncertainties. Difficulties encountered in the evaluation and forecasting of eartjquake losses appear to be due to lack of uniform inventories and damage data for key components in various lifeline systems. Water and transportation systems seismic risk analyses are included in two of the papers as examples of the methods. Three of the papers resulted from the Demonstration Project on Seismic Loss Estimation for Water Systems conducted by the TCLEE Seismic Risk and Water and Sewage Committees.(AU)