Loading...

Risk-based Prioritization of Highway Bridge Networks for Seismic Retrofit and Health Monitoring

Noorbala Tafti, Hamid Reza | 2023

110 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55907 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Mahsouli, Mojtaba
  7. Abstract:
  8. This thesis presents a probabilistic framework for prioritizing the highway bridge network for seismic retrofitting and structural health monitoring. The basis of this framework is the risk analysis of the bridge network, which includes bridges and the links connecting them in the transportation network. Risk is defined as the probability of exceeding the sum of all losses incurred to the community in the event of a hazard. These losses include the direct economic cost of bridge repairs and damage to vehicles due to bridge failure, the socioeconomic cost of increased travel time for transportation network users, the indirect economic cost of excess fuel consumption and depreciation of vehicles due to increased traffic, the direct and indirect social costs of injuries, fatalities, and life quality reduction due to bridge collapses, and finally, the environmental cost of increased pollutants, greenhouse gas emissions, and energy consumption resulting from both increased travel time and bridge repair operations. Prioritization for retrofit is based on seismic risk analysis and prioritization for health monitoring is based on risk analysis under service loads. The risk from both hazards, i.e., earthquake and service loads, is quantified using a host of probabilistic models and reliability methods. Seismic risk analysis is carried out using scenario sampling. Each sample in this analysis simulates a random scenario over a planning period, for example, 20 years. By regenerating random samples, the probability distribution of the total loss incurred to the bridge network in the event of an earthquake and the risk measure, i.e., the mean total loss, is computed. Retrofitting each bridge reduces the risk measure. The amount of the reduction is the benefit of retrofitting that bridge. The ratio of this benefit to the cost of retrofit is proposed as the priority index for retrofitting each bridge. Next, to prioritize bridges for health monitoring, the reliability index of each bridge is first calculated over time for service loads and various phenomena affecting the deterioration of the structure using system reliability analysis and the first-order reliability method (FORM). The limit-state functions in this analysis lead to the mean reliability index of the bridge over time. Changes in the standard deviation of the reliability index over time are also determined by fitting a relationship to the rating factor (RF) dataset extracted from the National Bridge Inventory (NBI) database. Then, by integrating the time-variant probability of failure over time and the sum of discounted loss caused by bridge failures over the nominal life of the bridge, i.e., 75 years, another risk measure, i.e., the expected cost of bridge failure, is computed. By monitoring the health of the bridge structure at intervals during its lifetime, observations on the safety status of the bridge are obtained. Bayesian updating using these observations diminishes the uncertainty of the structural reliability index and consequently, reduces the risk measure. The amount of risk reduction determines the “value of information” (VOI) obtained from monitoring each bridge. The priority index for health monitoring of bridges is then obtained from the ratio of VOI to the monitoring cost. The proposed framework is showcased through a comprehensive application on the large bridge network of Tehran, Iran. In this application, 552 bridges with various structural systems under 22 seismic sources are prioritized for retrofitting, and 224 bridges with slab-type structures are prioritized for health monitoring.


  9. Keywords:
  10. Prioritization ; Transportation Infrastructures ; Risk Analysis ; Reliability ; Seismic Retrofit ; Structural Health Monitoring ; First Order Reliability Method (FORM) ; Bridge Network ; Information Value

 Digital Object List

 Bookmark

No TOC