Question about temporary structural loading. 3

[3doorsdwn]

I've got a structure I'm designing that will be in place about 4 months (only for 4 months). The thing I'm trying to decide is whether or not to use full lateral loads or something less. I know ASCE puts out a standard on this [i.e. ASCE 37]....my question is (for anyone who has this standard): does this standard address load magnitude vs. specific duration time? And (if this is addressed and you feel generous): what kind of magnitude are we talking for 4 months duration (approximately)?

 

[nutte]

ASCE 37-02 allows you to reduce your wind speed based on the duration of construction. I know for a short duration (6 weeks or less, maybe?), the factor is 0.75. Your wind speed is squared, so the design pressure goes down to almost half. I don't have the document in front of me, so I can't say what it is for 4 months, but I would think it worth looking into.

I'd recommend buying ASCE 37-02. I don't think it is very expensive, and it will provide a lot more insight than the responses here. I'm also not sure it would apply to your temporary structure.

 

[DTGT2002]

The title of ASCE 37-02 is Design Loads on Structures During Construction.

It is not "Design Loads on Temporary Structures" for a reason.

If this structure will be used in a manner consistent with a permanent structure and we are discussing design for it as a finished product, I would not see a justification to even use 37-02.

There could be a justification for a reduced period based on the life of the strucutre, but in south GA during the summer, you run the risk of seeing the maximum events for the area, so I think you are back where you started from.

For the price of ASCE37-02 (or the new edition), it is still a document worth picking up, even if it only helps you understand what others should be doing in the construction process.

Hope it helps,


Daniel Toon

 

[zcp]

Being a fellow Georgia engineer, my vote is for full loads. Especially with the predicted hurrican season this year. This also sounds like a critical entrance to the plant so the savings versus risk doesn't seem like a good trade. Design for full loads and tell them 'it's the code'.

ZCP

http://www.phoenix-engineer.com

 

[SlideRuleEra]

3doorsdwn - I agree with DTGT2002 that ASCE 37 is for loads during construction, not for temporary structures (which will really be temporary).

IMHO, you will find better guidance in the International Building Code. The latest edition that I have is 2003. See Table 1604.5 "Classification of Building and Other Structures for Importance Factors". Category I includes "Certain Temporary Facilities" and allows the following factors for loading:
Seismic: 1.0
Snow: 0.8
Wind: 0.87 (with a footnote about hurricane prone regions).
These numbers may give you a general idea of what reductions are considered prudent.
However, for your case (this summer) I would give serious consideration to zcp's advice.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[3doorsdwn]

Thanks everybody!

 

[steellion]

Where I went to school, we had several classes in buildings that were designed to be temporary. In 1920. Still standing today.

 

[msquared48]

s my final comment here, it's all well and good that you are trying to save your client money. That's commendable and what we should do where warranted.

However, you have to temper that thought with the fact that if the structure fails, who is first in line to take the hit? It's you. Never forget that fact either.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[towerengr]

Public Safety, Liability, Professional engineer license - These are not worth risking because there is always a remote possibility something may go wrong. Having no knowledge about the pretzels with many twists, I would recommend a design with redundancies. If site conditions permit and there are no visual constraints on how the site may look, guying may be a cheap but effective option. When you design a support system for 85 mph wind, there is a very marginal cost penalty to upgrade to 95 mph. So, trying to fine tune the design to save money may not be worth the trouble considering the risk.