Bascule Bridge Statics 1

[LobstaEata]

Hi All

Got a discussion that's been going around the office and I thought it might be good to gain perspective from this group. Here's the long and short of it.

A bascule leaf span must be rated. The discussion revolves around where the critical section is located. Is it at the pin or the live load shoe? There is also a heel stop, but consensus is that this is not the critical section.

I look at it this way. The trunnion pin obvisously takes all the dead load while in operation and immediately prior to resting on the live load shoe. However, once the shoe is loaded the critical section for the rating should be taken at the shoe, since the live load effects on the cantilever are greatest at this point.

Your thoughts would be appreciated.

 

[wiktor]

The critical section will be at the live load shoe, and it will be for the moment and LL reaction, which, considering cantilever, could be subtancial, due to the amlification.
I've evaluated the bridge, where pin bearings were spring loaded from the top, allowing for small unplift prior to the engagement of the heel stops.