Propped Portal Frame

[cheshire1]

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

 

[JAE]

Its either change the size, or change the geometry somehow to increase the natural stiffness of the system.

 

[jike]

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.

 

[UcfSE]

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.