Eliminating an intermediate crane x-braced bay

[wds1]

I have been called by the owner to eliminate some intermediate x-bracing that is interferring with machinery operations. The building has 12 bays @ 25'in the direction of the runway beams. The runway beams are x-braced longitudinally in the 1st, 8th, and 12th bays for (2)10 ton cranes on the west and (1) 10 ton crane on the east side. The owner wants to eliminate the 8th bay of x-bracing on an interior row of columns. Without checking CMAA, my intuition would tell me that it is probably feasible since it is x-braced at either end. Any longitudinal load will be transferred to the end bays. One of the x-braced end bays would eliminate any axial compression from being applied to the runway beams. K-bracing would not eliminate the problem and creating a moment(or portal)frame would not work since they are Not as stiff as the x-bracing and therefore would not carry much load. What are your thoughts?

 

[bjb]

I think you have to run an analysis to see if the entire system, including foundations and remaining x braces still work. I agree that a portal frame won't attract as much load as the x braced bays. If your analysis indicates the remaining braced bays are overstressed, you might be stuck with trying to make portal frames work. I had a similar project a few years ago, and we had to add some portal frames. We made it work by adding portal frames in more bays than had x bracing removed. In our case, the x bracing was tension rod bracing. It seemed to work ok and we never received any complaints about our solution not working.