temporary bridge...full design?

[hopeengr]

I've been doing small (less than 75') temporary bridge designs for contractors doing DOT bridge projects. I was wondering how in-depth most temporary bridge designs are. I tend to want to treat it as a permanent structure (performing all the LRFD checks), however in reviewing past designs, it seems others take short cuts such as not performing code checks (just following beam theory, more or less). Also, is it common to design every detail such as diaphragms, stiffeners, connections, bolts, welds, etc or just use standards/typicals. I will add that I am not utilizing any software, nor were the other designers.

 

[bridgebuster]

The age old question: How temporary is temporary?

Your design has to comply with the requirements of AASHTO and the DOT that the contractor is working for. I think LRFD is a bit too much for a temprary bridge, particularly if it might only be in place for one season. We've designed several in the last few years and the DOT has usually been flexible on the details.

The following is a link to NYSDOT Standard Specs, click on Section 619 (which is MPT), it has a spec for temporary bridges.

https://www.nysdot.gov/portal/page/...g/specifications/2002-standard-specifications

 

[Qshake]

AASHTO has a publication for temporary works. I suggest that you get a copy.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[hopeengr]

bridgebuster: Thanks for the link. I'll check it out to see their take on the situation.

Qshake: I have 2 guides from AASHTO on Temporary Bridge Works (Design Guide Specifications & Construction Handbook) but both deal primarily with temporary structures used in conjunction with constructing a bridge (temporary shoring, formwork, etc) Is there another publication dealing specifically with temporary bridges?

 

[DRC1]

Ratey has a good book. I will check the title in the morning. I usually do not design for seismic, depending on the nature of the use may allow for some overstress, and may relax some serviceabilty requirements depending on use. Temporary structures require a lot of judgement as codes are not as clear, But just because they are temporary, no less attention should be given to them than permenant bridges and strength should be carefully checked. A careful analysis of loading conditions should be done as they may not be as easy to define as permenat bridges.