×
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

ASCE 7-10 Wind loads on rooftop platform

ASCE 7-10 Wind loads on rooftop platform

ASCE 7-10 Wind loads on rooftop platform

(OP)
I am designing a platform to hold equipment on top of a building. I have already calculated my wind pressure. I am a bit confused on the force coefficient to use. I know to use Figure 29.5-1 for the force coefficient on the equipment, but unsure on what figure to use for the force coefficient on the platform itself. I am thinking I use the force coefficients in figure 29.5-2. The platform has four pipe columns, the beams are made out of wide flanges and channels and i have knee braces to stabilize the structure.

It would greatly appreciated any help on the correct way to calculate the wind force on the platform.

RE: ASCE 7-10 Wind loads on rooftop platform

Which edition of ASCE 7?
It's possible that an uncommon geometry simply may not be covered by the standard. I suspect a platform above a building could have large uplift forces that aren't covered by the projected-area methods. Also note the section dealing with increased loading for rooftop equipment.

RE: ASCE 7-10 Wind loads on rooftop platform

I will check tomorrow, but above a certain height, you have to increase thenpressyer, I believe as much as 30 percent.

Mike McCann, PE, SE (WA)


RE: ASCE 7-10 Wind loads on rooftop platform

In these environs... the bigger problem is usually snow accumulation.

Dik

RE: ASCE 7-10 Wind loads on rooftop platform

(OP)
I am using the ASCE 7-10 third printing. And my rooftop is about 100' in the air. And our live load governed over our snow load.

RE: ASCE 7-10 Wind loads on rooftop platform

(OP)
Also, when I am applying my ice weight to my structure. Would the equipment on the platform have ice weight?

RE: ASCE 7-10 Wind loads on rooftop platform

Quote:

I am a bit confused on the force coefficient to use. I know to use Figure 29.5-1 for the force coefficient on the equipment, but unsure on what figure to use for the force coefficient on the platform itself. I am thinking I use the force coefficients in figure 29.5-2. The platform has four pipe columns, the beams are made out of wide flanges and channels and i have knee braces to stabilize the structure.

Yes, getting Cf from 29.5-2 (and loading each individual member for wind) would be one acceptable approach.

Also keep in mind that there is a uplift case to consider with rooftop equipment/framing.

Quote:

Also, when I am applying my ice weight to my structure. Would the equipment on the platform have ice weight?

Unquestionably. (Unless it runs hot/warm.....and even then I'm not sure you should ignore the ice load because you can always lose power in a ice storm.)

RE: ASCE 7-10 Wind loads on rooftop platform

(OP)
Thank you WARose for responding. Section 29.5.1 is for "Rooftop structures and equipment for buildings h<60ft" if my building is greater then 60ft does this section still apply?

RE: ASCE 7-10 Wind loads on rooftop platform

Quote:

Section 29.5.1 is for "Rooftop structures and equipment for buildings h<60ft" if my building is greater then 60ft does this section still apply?

I didn't notice your height until after I posted. I think at that point, you can use Part 6 of Chapter 30 (C&C).

RE: ASCE 7-10 Wind loads on rooftop platform

(OP)
Thank you that is helpful, I should of posted my height in my original post. When I am calculating my ice load of the equipment, do I use equation 10.4-1 to get my ice weight?

RE: ASCE 7-10 Wind loads on rooftop platform

Quote:

When I am calculating my ice load of the equipment, do I use equation 10.4-1 to get my ice weight?

I think we are talking (then) more of a structure composed of flat surfaces. (I.e. then you would figure it by volume, ergo Eq. 10.4-2.)

To go back to the wind load for a second (while it is on my mind), I wanted to say: I went to a seminar on wind loading (based on ASCE 7-10) some years back and the guy giving it said that the wind load on rooftop structures with h ("reasonably") greater than 60' is just about what you get if you did it by that section anyway. At the time, I don't think they had the research to justify it in excess of that. Not sure if that has changed since. (I know that is not much of a source.....but I thought I'd mention it anyway.)

RE: ASCE 7-10 Wind loads on rooftop platform

(OP)
Yeah, equation 10.4-2 makes a lot more sense.

So basically there just isn't enough research on rooftop equipment above 60ft get mentioned in asce 7-10. Just to double check, the uplift acts simultaneously with lateral wind force on the equipment?

RE: ASCE 7-10 Wind loads on rooftop platform

(OP)
Also, since my platform deck is metal grating, does that mean I have to consider a ice weight on it?

RE: ASCE 7-10 Wind loads on rooftop platform

Quote:

Just to double check, the uplift acts simultaneously with lateral wind force on the equipment?

That's what I've typically done. (In the proper combination with minimal Dead Load.)

Quote:

Also, since my platform deck is metal grating, does that mean I have to consider a ice weight on it?

Most definitely.

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! Already a Member? Login


Resources

eBook - Manufacturing the Cars of Tomorrow
In this ebook, we'll explore how additive manufacturing is going to transform the way cars are made. This includes commentary from thought leaders such as Ford's CTO, Ken Washington, Customer case studies of ways 3D printing is being used today, and a variety of part examples where 3D printing is already impacting how automobiles are made. Download Now
White Paper - Smart Manufacturing for Semiconductor
New technologies and approaches present great opportunities for semiconductor manufacturers to achieve high levels of innovation, yield and improvement. This white paper explores some of these cutting-edge technologies and how they can be applied effectively in the semiconductor industry. Read about how Smart Manufacturing is transforming the semiconductor industry. Download Now
White Paper - Analysis and Simulation in Aircraft Structure Certification
Organizations using simulation and analysis tools effectively see the benefits in their ability to achieve certification faster and with drastically less total cost than those who do not maximize these tools. Read this White Paper to learn about how digital tools such as analysis and simulation help in aircraft structure certification. 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