Retrospective Analysis of Hydraulic Bridge Collapse

Abstract

The investigation concentrates on the most predominant cause of bridge collapse (239 or 55%), which is the result of hydraulic effects. Out of all the causes of bridge collapses, the National Bridge Inventory (NBI) and constructed control groups found that hydraulic collapse diverges significantly. The control group consists of randomly selected bridges from the 2017 NBI, controlling for age and other parameters. The study of hydraulic-collapsed bridges yields statistical trends through nonparametric tests. Results for hydraulic collapse include an annual failure rate of approximately 1 out of 8,500. Structural deficiency is associated with hydraulic collapse at a rate of 44% in comparison to the control group, which has a rate of 15%. Precollapse evaluations for hydraulic-collapsed bridges and the control group are scour critical at a rate of 17% and 6% and scour stable at 83% and 94%, respectively, when nonscour-evaluated bridges are omitted. Precollapse substructure condition rating is poor for 34% of bridges and is lower, or 11%, for the control group. The substructure condition rating is a better indicator of collapse than the scour critical appraisal rating; additionally, scour is paired with less hazardous conditions (e.g., minor cracking with minor scour). Consequences are limited for hydraulic collapses compared to other causes of collapse in terms of average daily traffic traversing the structure and life loss. Maintenance issues are presented to reduce hydraulic bridge collapse with consideration for underwater inspections and flood events.