Deflection of PEB with crane 1

[vohai]

Hi all!
I am designing an industrial building with bridge crane rated capacity 15 Ton. Because of poor soil in the site I try to design frame support pinned.
The broblem is lateral deflection due to wind load is very hight. But in our building code there is no deflection limit for steel frame at the height crane for wind load. The code only restricts deflection due to lateral crane load not exceeds H/1250.
Deflection from wind load for my calc is 110mm in left column and 90mm in right column. One of my coleage said only the difference of deflection that counts.
I am afraid that crane will fall some day.
What is your opinion?

 

[JAE]

Transverse deflection of 110 mm seem very high - Most crane columns are dual (2) columns tied together with lateral truss members to make a very stiff column.

The outside column extends up to support the roof of the building while the inside column extends up to support the crane beams under the track.

With this "truss" you can significantly stiffen the columns to act like vertical cantilevers coming out of the ground, and still assume each column (each chord of the truss) is pinned at the base.

 

[vohai]

Thank you for your help. But I am afraid that the 2-branched column is not pinned for foundation. Each of branch tranfers axial load only, but the pair of axial load induce moment for foundation. The system is good only if two columns have a distance from each other to sit in 2 isolated foundation. In my case portal frame with pinned support is easier for design foundation. (The lateral load all transfer to R.C. slab on grade).
I still have a question that what the relative of absolute diflection of frame at the height of crane for wind load is acceptable, and should I use P-delta analysis for that value?

 

[SlideRuleEra]

Have you considered using the AISC Code of Standard Practice For Steel Buildings & Bridges as a guideline? Paragraph 7.11.3.1 (page 5-238, in my copy of AISC Manual of Steel Construction, 9th Edition, ASD) covers allowable deviation for columns during steel erection. Limit is 1:500, with other factors to be considered.

This is not what you are looking for, but there are not always direct answers to our technical problems. If more applicable information becomes available, use it.

In any event, I would suggest an absolute defection substantially less that the depth of the column, maybe the smaller of Depth/6 or 1:500.

 

[aggman]

Check with the Metal Building Manufacturers Association (MBMA). They should have the information you need. Just type MBMA in google and it will take you there. I pulled the following two paragraphs from their website.

Does MBMA establish erection tolerances for metal buildings? If so, what are they?
Erection tolerances are addressed in the Common Industry Practices Section of the 1996 Low Rise Building Systems Manual, page IV-6-3 (see question No. 3 for a discussion of Common Industry Practices). Erection tolerances are those set forth in the AISC Code of Standard Practice, except individual members are considered plumb, level and aligned if the deviation does not exceed 1:300. When crane support systems are part of the metal building system, additional erection tolerances are specified in Section 9 of the Common Industry Practices.

What are the limitations on allowable drift (sidesway) in metal buildings?
This topic is addressed in the AISC’s Steel Design Guide Series No. 3: Serviceability Design Considerations for Low-Rise Buildings, as well as in the 1996 MBMA Low Rise Building Systems Manual . The limitations for drift vary, depending on the type of material attached to the framing and the tolerance for movement. For example, for metal panels attached to framing, the recommended maximum drift is between H/60 and H/100 where H is the building height. It is also recommended that the wind load used to compute the drift when checking against these allowable limits should be based on a 10 year recurrence interval, which is approximately equal to 75% of the normal 50 year design wind pressure. For other types of cladding, refer to the references cited for more discussion.