×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Rooftop Unit Equipment Load

Rooftop Unit Equipment Load

Rooftop Unit Equipment Load

(OP)
Hello,

I have a question regarding catwalks at the rooftop. As per ASCE7-05, the uniform load is 40 psf and concentrated 300 lbs. Are these laods supposed to be applied together? I can't seem to find any text mentioning otherwise.

Thanks

RE: Rooftop Unit Equipment Load

IMHO, yes, apply the loads simultaneously.

My reason has nothing to do with the document's text, just engineering judgement:

If the catwalk is designed so "closely" that adding exactly one, 300 lb. concentrated load (anywhere on the catwalk) to a 40 psf UDL makes the structure "unsafe", the design is unrealistically "precise".

www.SlideRuleEra.net idea

RE: Rooftop Unit Equipment Load

(OP)
That's true. Thank You for the input.

RE: Rooftop Unit Equipment Load

In ASCE 7-10, 4.4 explicitly states it is either uniform OR concentrated, whichever produces the worst effect.

RE: Rooftop Unit Equipment Load

cgstrucg,

The Code does not require the UDL and the Concentrated loads to be applied concurrently. Essentially the UDS is for main carrying member design, and to provide sufficient mass in the building for the VFRS and the LFRS. The concentrated load often controls the grating design and the grating supports.

RE: Rooftop Unit Equipment Load

Long ago, my brother worked for a pacemaker manufacturer.
The pacemakers had a lead on them that the surgeon trimmed to length when installing it.
So as long as it was plenty long, it didn't really matter how long.
But, it was a highly regulated industry, so it had to be just so-so on paper.
So their slogan was "Measure it with a micrometer, mark it with a piece of chalk, cut it with a hatchet."
So, if I calculate seismic loads to 10 decimal places, that's the thinking behind it.
On the loads there- yes, see 4.4 and also note that it defines how big a "concentrated" load is. Also, see the load combinations in Chapter 2.
OSHA has some load requirements for stairs and ladders, but I don't see anything specific for general walking surfaces.

RE: Rooftop Unit Equipment Load

Cgstrucg:
The 300lb. concentrated load is sorta supposed to represent a 250lb. worker and 50lbs. of tools and equipment, per OSHA and others. Then, I wonder if you’ve ever seen two guys working close together on something, plus a few pieces of pipe or other bldg. material laying on the catwalk? I’m inclined to agree with SRE and also agree with jittles thinking, ‘which ever produces the worst loading.’

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources

eBook - Efficient and Effective Production Support with 3D Printed Jigs and Fixtures
Jigs and fixtures offer manufacturers a reliable process for delivering accurate, high-quality outcomes, whether for a specific part or feature, or for consistency across multiples of parts. Although the methodologies and materials for producing jigs and fixtures have evolved beyond the conventional metal tooling of years past, their position as a manufacturing staple remains constant due to the benefits they offer. Download Now
Overcoming Cutting Tool Challenges in Aerospace Machining
Aerospace manufacturing has always been on the cutting edge, from materials to production techniques. However, these two aspects of aerospace machining can conflict, as manufacturers strive to maintain machining efficiency with new materials by using new methods and cutting tools. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close