Skew steel bridge with no cross-beams
Skew steel bridge with no cross-beams
(OP)
I am Reviewing an Existing steel bridge. the Bridge is very skew, average Span = 40meters, main girder depth = 2.00meters and you can say NO cross-girders.
My questions are:
1-is there is any specs about the analysis/design of such bridge with No cross-beams
2-I run the normal grillage analysis and the girders were safe, but am I missing any other strains because of the "no X-girders issue"
3-if, we assume No lateral torsional buckling, No wind , No seismic, why do I need the cross-frames for?
thanks for your assistance in advance
My questions are:
1-is there is any specs about the analysis/design of such bridge with No cross-beams
2-I run the normal grillage analysis and the girders were safe, but am I missing any other strains because of the "no X-girders issue"
3-if, we assume No lateral torsional buckling, No wind , No seismic, why do I need the cross-frames for?
thanks for your assistance in advance





RE: Skew steel bridge with no cross-beams
How can you assume no lateral torsional buckling and no wind?
RE: Skew steel bridge with no cross-beams
Yes I have a Composite deck. I modeled the deck as a shell/plate element with a very weak properties in case of dead load, i.e. wet concrete and with the right properties in case of superimposed dead and live load.
What I mean by there is no lateral torsional buckling and no wind, is according to NSBA/AASHTO, the function of the cross frames is following:
1-prevent lateral torsional buckling
2-transfer wind/ lateral loading to support
3-reduce the differential deflection between different girders at the same location
4-reduce flange lateral bending and torsion in case of Skew/and curved bridges, knowing that part of the flange lateral bending or torsion that exist in the skew bridges result from the action of cross-frames trying to reduce differential deflection.
So if 1& 2 is some how prevented, are points 3 & 4 will make a problem to me.
Moreover, I don't remember seeing any skew bridge with No cross-frames and neither I remember that the AASHTO addressing the possibility of such situation
RE: Skew steel bridge with no cross-beams
I can't speak to whether they are absolutely required at your location if calculations show that they are not needed. Here in the states, the governing DOT would have an opinion. I have always found them necessary at the bearings to transfer seismic loads to the substructure.