A 20TH CENTURY BRIDGE MEETS A 21ST CENTURY SHIP
The Francis Scott Key Bridge was constructed by way of the mid-Seventies and opened in 1977. The primary construction over the navigation channel is a “steady truss bridge” in three sections or spans.
The bridge rests on 4 helps, two of which sit either side of the navigable waterway. It’s these two piers which are vital to guard in opposition to ship impacts.
And certainly, there have been two layers of safety: A so-called “dolphin” construction constructed from concrete, and a fender. The dolphins are within the water about 100m upstream and downstream of the piers. They’re supposed to be sacrificed within the occasion of a wayward ship, absorbing its vitality and being deformed within the course of however holding the ship from hitting the bridge itself.
The fender is the final layer of safety. It’s a construction fabricated from timber and strengthened concrete positioned round the primary piers. Once more, it’s supposed to soak up the vitality of any influence.
Fenders usually are not supposed to soak up impacts from very massive vessels. And so when the MV Dali, weighing round 100,000 tonnes, made it previous the protecting dolphins, it was merely far too large for the fender to resist.
Video recordings present a cloud of mud showing simply earlier than the bridge collapsed, which can nicely have been the fender disintegrating because it was crushed by the ship.
As soon as the huge ship had made it previous each the dolphin and the fender, the pier – one of many bridge’s 4 principal helps – was merely incapable of resisting the influence. Given the scale of the vessel and its doubtless pace of round 8 knots (15km per hour), the influence drive would have been round 20,000 tonnes.
