question for any civil engineers/bridge builders?

BDG · 13-May-2005, 16:34

Sorry to ask this on the board but someone may know the answer.

I come through roadworks on the M60 where they are building several new bridges.

Why do you have the not inconsiderable bulk of a bridge span supported by a small contact patch between the span and the actual upright support of the bridge. The contact patch appears to be about 10% of the top of the upright.

Surely this must concentrate the load on a small area rather than spread the load.

I hope that makes sense from the description.

???

moto748 · 13-May-2005, 22:29

Because the bridge is designed to have a virtual "knife-edge" support. Hence it is "pin-jointed" (if it's an end span).

This means that no unwanted bending forces are transmitted to the supports, or the bridge itself. The bridge is free to "rock" a little at the support.

rockhopper · 13-May-2005, 22:39

good answer!

BDG · 14-May-2005, 01:04

Thank You Moto748.

I will file that gem of information away and in 10 years time at some diner party when someone else asks i'll sound really clever, even though i'm not

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13-May-2005, 22:29	#2
moto748 Registered Forum User Big Twin Posts: 1,385 Join Date: Apr 2004 Because the bridge is designed to have a virtual "knife-edge" support. Hence it is "pin-jointed" (if it's an end span). This means that no unwanted bending forces are transmitted to the supports, or the bridge itself. The bridge is free to "rock" a little at the support. Reply

13-May-2005, 22:39	#3
rockhopper Registered Forum User Ducati Corse Posts: 3,367 Join Date: Jul 2001 Location: Pinxton good answer! Reply

14-May-2005, 01:04	#4
BDG Registered Forum User Ducati Corse Posts: 3,893 Join Date: Sep 2003 Location: The North Mood: Daft as MartinH after too much Smirnoff Ice Thank You Moto748. I will file that gem of information away and in 10 years time at some diner party when someone else asks i'll sound really clever, even though i'm not Reply