This paper describes a method of evaluating seismic system performance of transportation network. The results are shown to demonstrate post-earthquake traffic behavior in animation. This will assist emergency response professionals to gain pre-event insight for developing optimal emergency response strategy. The basic element that plays a crucial role here is the fragility information for highway bridges in Caltrans' Freeway network. The fragility information is expressed as a function of the ground motion intensity, such as peak ground acceleration (PGA) or peak ground velocity (PGV), and is obtained empirically on damage database associated with the 1994 Northridge earthquake. The PGA and PGV values for the bridges are acquired from the TriNet ShakeMap. In this paper, the bridges are classified into different groups according to their structural characters and soil conditions. Based on the information, the fragility curves for different levels of damage are developed with the aid of the maximum likelihood method. The fragility information thus developed is integrated into the Monte Carlo analysis involving traffic flows, and degradation of traffic capacity of Caltrans' network in Los Angeles and Orange County damaged by the Northridge earthquake is evaluated. Furthermore, the network analysis results on the basis of fragility curves based on PGA and PGV are compared. Finally, the simulation results are compared with the actual performance of Caltrans' network during the Northridge earthquake. This comparison shows that the seismic analysis based on the fragility information is very reasonable, and hence the animation of simulated traffic flow is quite useful.
This paper describes a method of system performance evaluation for electric power network. The basic element that plays a crucial role here is the fragility information for transmission system equipment. The method utilizes the fragility information for evaluation of system performance degradation of LADWP's (Los Angeles Department of Water and Power's) power network damaged by a severe earthquake by comparing its performance before and after the earthquake event. One of the highlights of this paper is the use of computer code “PowerWorld” to visualize the state of power flow of the network, segment by segment. Similarly, the method can evaluate quantitatively the effect of various measures of rehabilitation or retrofit performed on equipment and/or facilities of the network. This is done by comparing the system performance with or without the rehabilitation. In this context, the results of experimental and analytical studies carried out by other researchers are used to determine the possible range of fragility enhancement associated with the rehabilitation of transformers in terms of base-isolation systems. In this analysis, 47 scenario earthquakes are used to develop the risk curves for the LADWP’s power transmission system. The risk curve can then be correlated to economic impact of the reduction in power supply due to earthquake. Recovery aspects of the damaged power system will be studied from this point of view in future.
Damage to highway systems from recent earthquakes has emphasized the need for pre-event damage assessment of the existing highway systems so that the effective measures can be taken to reduce the loss from the future earthquake. In this paper, a Monte Carlo technique is presented which can be effectively used to simulate the states of bridge as well as highway network damage. With the aid of damage data, collected after the 1994 Northridge earthquake, the fragility curves are developed for each bridge on a limited access expressway network in Los Angeles County and Orange County in California, and classified in accordance with such attributes as whether it is a single span or multiple span, how much it is skewed and the condition of soil on which it is constructed. Monte Carlo simulations of states of bridge damage are performed based on these facility curves. A set of criteria and indices are then introduced, upon calibration with Northridge experience, for simulation of the damage state of each link and then the state of network damage when subjected to scenario earthquakes. The calibration is achieved by adjusting the criteria and indices by comparing the simulated states with the actual states of network damage under the Northridge earthquake. Computational time for one realization (simulation) of states of network damage is of the order of a few seconds. Therefore, the Monte Carlo simulation-based method of network damage assessment presented here can provide a post-earthquake response decision support system for highway networks; Since the purpose of the present study is to demonstrate the efficacy of the Monte Carlo simulation method, numerical examples are performed under the conditions that only bridges are seismically vulnerable, bridge fragility curves are available, and knowledge of the state of network damage suffices for government agencies and emergency response profession to make decisions as to how search/rescue/medical teams and emergency repair crews can be dispatched and how food, potable water and other emergency supplies can be transported by an optimal use of the remaining network capacity. In this study, the spatial distribution of ground motion intensity is estimated deterministically in terms of peak ground acceleration (PGA). The spatial variation of PGA due to modeling and other sources of uncertainty is expected to have some effect on the final result. This issue is currently under study.
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