pedestrian bridge bw two 10 stories tower

huangyhg

pedestrian bridge b/w two 10 stories tower
two towers of 10 stories are 30ft apart, and there is a need of pedestrian bridge on every story level between the two towers. building is in zone-iii. the principle design engineer thinks that it cannot be bridged with a steel structure pedestrian bridge as the buildings are expected to sway upto 4 inches with different mode shapes, also the second mode shape when both buildings sway towards each other the bridge will come apart.
my question is that is he right ? and is there anyway that we can fit in a steel girder bridge between two towers or not ? how will the joints be detailed to cater building's movement in different mode shapes. ?

i would've thought that you could anchor the bridge on oe tower, and have a sliding support on the other.
of course you could always tie the towers together with thebridges, which would change their mode shapes, and re-do the analysis.
the building is already constructed.
i second the idea of fixing the bridge to one building and provide slide bearing connection on the other. you can detail the bridge to move and provide the required expansion joint at one of the building/bridge interfaces.
when two towers are moving away ! thats like 4" + 4" = 8". eight inch slide brearing plate connection /??
that's one of the most screwed up problems i've heard of!!
you can certainly detail a sliding connection at one end to allow that much movement.  other than some crazy joint like on the petronas towers, i don't see any other way to do it.  
one question is serviceability during frequent wind events.  for example, if the wind blows 30 mph (arbitrary number), how much will the connection have to slide?  enough that people will notice and freak out?
be careful interpreting the mode shapes.  models are far from perfect at predicting these.  for example, i've seen people come up with modes that seemed to indicate that the bldgs would move in sync.  there's no way i would rely on that much precision.  for one thing, the eigenvalue analysis is linear and there are usually numerous violations of the underlying assumptions.  for example, the structure will almost certainly have some non-proportional damping so the mode shapes will be complex to some degree.
i agree with the others. one end of the bridge is anchored to one of the towers, the other is allowed to moved.
not sure how else this can be done.
if your uncomfortable with a sliding joint, you might want to consider a rocker joint at the moving end. frequently used on bridges to provide movement. though 8" of movement will be quite a bit, and take a very deep rocker to accomadate. fortunately, with only a 30' span, your reaction loads should be relatively small.
thanks 271828  
tell me! how about having a sliding bearing plate on both ends rather one fixed and one with sliding bearing plate ! and please help find a typical detail of sliding bearing plate for such joint?
how about a vertical rocker on one end and horizontal slider on the other?  how will fixed on one end work when there is a vertical component to the movement, won't it deflect and / bend?
rope bridges would be cool
seems to me you could have problems not just with the large movements but with continual small movements; would tend to wear out things or start making noise when moving.
you'd also want to allow a lot more movement than what is calculated- could get exciting if you drop that top bridge on one end.
i assume these would increase the wind load quite a bit as well.