propped portal frame

huangyhg

propped portal frame
hi
i am designing a propped portal frame at present. it has gantry cranes on either side of the central column. i am finding that the horizontal displacements at crane level are too high. the crane manufacturer recommends a tolerance of 10mm. can anyone recommend a way i could keep the displacements at a minimum without having to increase the size of my members.
many thanks   
its either change the size, or change the geometry somehow to increase the natural stiffness of the system.
have you used fixed bases on the columns? make sure that your footings, anchor bolts and base plate are designed to limit rotation of the columns.
knee braces might help out if you have room or clearance for them.  x-bracing would be better.  i agree with jike, fixing the column base would help.  that means your footings will be 2-3 times bigger and connections will be bigger as well. of course you can just use larger/deeper columns and beams if they fit.