Pot bearings on curved girder bridge

[tphel]

I have a 5 span curved girder steel bridge with 125' end spans and 180' middle spans. The piers and abutments are all laid out radially and the third pier (or 4th support) is fixed while the remaining supports are expansion. I was wondering at what angle the guided pot bearings should be placed on the supports? Should they be oriented at a straight line to the fixed bearing point or at a tangent to the curve?

 

[VoyageofDiscovery]

Hi tphel,

Both orientations have there benefits and disadvantages, and there are no hard and fast rules. It is better to minimize the introduction of forces and deformations so, typically I place my bearings at the abutment tangent to the curve to allow movement at the expansion joint without distortion and place the bearings at the piers in line with the centre of fixity at the third pier.

Regards

VOD

 

[tphel]

VOD,

Thank you for your prompt reply, one further question, at what angle should I place my fixed bearing, should that be at a tangent with the curve as well?

TP

 

[wiktor]

The guided bearings should be placed at straight line(s) to the center of fixity for the bridge (typically a point at the middle of the fixed support). It is also possible to place these bearings at the tangent to the curve, but only when the degree of the curvature is small, and when you will be able to accommodate transverse movement at the bearings by specifying additional free play at the guides. Curved bridges typically behave as rigid bodies due to the presence of full depth diaphragms, so accommodation of transverse movement at the supports by flexing of the webs is not achievable.

 

[VoyageofDiscovery]

A fixed bearing is fixed for translation in all directions anyway. But for the sake of it, yes, tangent to the curve to line up any anchor bolts to the pier cap.

Regards

VOD