The Moving Ahead for Progress in the 21st Century Act (MAP–21) requires that each state develop a “risk-based asset management plan” and declares that “it is in the vital interest of the United States … to use a data-driven, risk-based approach and cost-effective strategy for systematic preventative maintenance, replacement, and rehabilitation of highway bridges and tunnels to ensure safety and extended service life.” The legislation does not specify a method or performance measures for considering risk. However, the language makes clear the desirability of incorporating risk in a way that can reasonably be supported in a data-driven cost-effective process.
Risks of interest include exogenous uncommon hazard that acts on a bridge or a small subset of bridges at random timing and location, and causes a loss of access, seriously degraded functionality for road users, unexpectedly rapid deterioration, or unexpectedly high cost. For these types of risks, it may be possible to estimate hazard likelihood at the level of geographic zones or structure categories, and vulnerability or resilience at the level of individual assets. This probabilistic approximation may enable an agency with suitable tools to quantify and manage risks in a data-driven cost-effective manner even if the exact risk for each bridge can never be measured or the timing of event is not exactly known.
The hazards satisfying these criteria may include, but are not limited to, earthquakes and other types of earth movement, hurricanes and tornadoes, floods and scour, fires, vehicular or vessel collisions, fatigue, and advanced deterioration. These hazards have consequences that are beyond the normal deterioration and functional deficiencies already assessed in bridge management systems. The probability of each hazard and the ability of each structure to resist the hazard are not always consistently and quantitatively assessed at the current state of the practice.
The objective of this research is to develop proposed AASHTO guidelines for a data-driven risk assessment at the bridge and structure level. At the minimum, the guidelines should consider risks from natural and man-made hazards and should be suitable for use in a bridge management system.