Awwwwww......... It looks like the unique A-frame movable bridge over Mantua Creek is no more. Terrible collapse!
http://www.rrpicturearchives.net/showPi ... id=3261046
Railroad Forums
Moderator: David
But I knew better. I knew the cause right off, having an understanding of the engineering principles behind the bridge: it was compromise of the abutment support function. You see, that A-frame and those stringer cables do not support the weight of a train when the bridge is "closed" (closed for boat traffic, open for rail traffic). In that position, the "deck" (the part that can swing open) rests on the abutments so that the bridge functions in that position as a simple deck girder bridge, with girders supported at both ends by pilings or whatever. The A-frame and stringer cables are only called upon to support the deck when it is in the "open for boats" position. The stringer cable snapped when the abutment gave way somewhat and the weight of the train caused a shifting of the deck in its closed position, putting too much stress on those cables.http://www.thewhistlepost.com/forums/ra ... ridge.html
Steve F45 wrote:is that just fog or a haze from the leaking cars?It happened early in the morning near the water, so it might just be fog. However, vinyl chloride is a gas at atmospheric pressure and normal temp, so maybe its that as well. Pretty eerie looking either way.
jstolberg wrote:The cause of the failure may not have been due to the steel, but due to the abutment below.I've seen in other forums people say it might have been a miter joint problem, causing the derailment, not a structural failure. But I think the above comments are right on -- if you look at this news video, around the 2:30 mark, you can see the north end of the bridge (left in this view) is sunken -- the rail support clearly appears to have buckled centered on the middle of the bridge - consistent with the above comment about abutments supporting the load on either end and one of them failing. JS
From a model railroader's chat:But I knew better. I knew the cause right off, having an understanding of the engineering principles behind the bridge: it was compromise of the abutment support function. You see, that A-frame and those stringer cables do not support the weight of a train when the bridge is "closed" (closed for boat traffic, open for rail traffic). In that position, the "deck" (the part that can swing open) rests on the abutments so that the bridge functions in that position as a simple deck girder bridge, with girders supported at both ends by pilings or whatever. The A-frame and stringer cables are only called upon to support the deck when it is in the "open for boats" position. The stringer cable snapped when the abutment gave way somewhat and the weight of the train caused a shifting of the deck in its closed position, putting too much stress on those cables.http://www.thewhistlepost.com/forums/ra ... ridge.html
95 years of age and scour and hurricanes have taken their toll.
Steve F45 wrote:is that just fog or a haze from the leaking cars?It was foggy but the low cloud around the cars is almost certainly vinyl chloride.