Vessel Collision Design Loads
This is one of my favorite relics from working at Caltrans; not because of any great thing I did but in what lies between the lines. A (chemically impaired) ship pilot missed the 2300+ft wide opening of the SFOBB west spans and hit a pier; 53,000 gallons of oil poured into the Bay. Ole' George from the NTSB was tasked to investigate Caltrans: Why is the bridge pier where it is? Why did the bridge fenders cause so much damage to the vessel? He knew the questions were ludicrous, but he did his job and I somehow answered without a snide voice. God bless George wherever he is.
Fast-forward to Baltimore and collapse of the Francis Scott Key Bridge. Presumably the bridge will be replaced with a structure having more resiliency i.e. redundant load paths and a robust fender system. Wind loads may well dominate. Still what magnitude of collision should be designed for, given the unlikely event of an errant vessel? That could be a humongous site-specific risk analysis of debatable value.
Deputy Project Manager at California High-Speed Rail Authority
11 个月Sue, thanks for sharing your story. The COSCO Busan has a deadweight tonnage (DWT) of approximately 67,000 tonnes and was moving at about 10 knots, in contrast to the Dali, which has a DWT of 120,000 tonnes and was traveling at about 8 knots. The momentums of the two ships are not significantly different. Fortunately, the COSCO Busan had a sideways slide with the Bay Bridge, whereas the Dali made a direct frontal hit. The damage to the Busan's hull also acted somewhat as a cushion for the bridge. Additionally, the Bay Bridge's fender system provided some cushioning and added mass. Most importantly, the Bay Bridge pier, after its seismic retrofit, must have a much larger lateral capacity. All being said, a direct hit could still cause some permanent damage to the bridge, although it might not lead to a collapse. It was a close call.