Pressures at mid-height of building - ASCE

[firstoption]

I can't figure this out reading the ASCE 7-10

Are pressures different say between:

- 10th floor windows/roof-covering in 10-story tall building
- 10th floor windows/roof-covering in 20-story tall building

(sometimes from the design, you see shingles or membrane covering at other places besides the roof)

if they are, what are the changing in the equations used?

 

[mike20793]

Yes. For the first example, your building height is only 10 stories, but for the second example its 20 stories. The component and cladding pressures are directly dependent on the height of the building since it affects how wind travels over or around the structure.

 

[firstoption]

Yes. For the first example, your building height is only 10 stories, but for the second example its 20 stories. The component and cladding pressures are directly dependent on the height of the building since it affects how wind travels over or around the structure.

thanks
that's what I thought by just using logic, but i can't seem to figure out the equations and how they'll differ.

is it a constant from a table that would make the difference?


I've taken a hurricane course in grad school but that was so long ago

 

[SteelSlugged]

ASCE's wind load provisions are difficult enough for seasoned veterans in the structural field, so it will be very difficult to explain how to use the code to someone new to it. I learned wind provisions by having a more experienced engineer point out my mistakes, regardless of how much care I thought I was applying.

Having said that, pick up a copy of ASCE's guide to using the wind load provisions. It is a very helpful guide. Read the commentary in ASCE.

 

[calvinandhobbes10]

Kz is the variable that changes

 

[firstoption]

ASCE's wind load provisions are difficult enough for seasoned veterans in the structural field, so it will be very difficult to explain how to use the code to someone new to it. I learned wind provisions by having a more experienced engineer point out my mistakes, regardless of how much care I thought I was applying.

Having said that, pick up a copy of ASCE's guide to using the wind load provisions. It is a very helpful guide. Read the commentary in ASCE.

The first sentence on my original post was "I can't figure this out reading the ASCE 7-10"

Kz is the variable that changes

I don't think this changes due to overall building height. It is simply factor at elevation in question

 

[EZBuilding]

The negative (suction) pressure on a building is based upon q[sub]h[/sub] not q[sub]z[/sub]. Look at figure 27.4-1 of ASCE 7-10.

 

[cal91]

The first sentence on my original post was "I can't figure this out reading the ASCE 7-10"

That's exactly what he's addressing... he's validating the fact that it's difficult to figure out the wind load provisions from ASCE 7-10 and offered you resources to better understand it.

SteelSlugged... I'd like to read the guide. Is it one of their design guides? I can't seem to find it in my firms library of Design Guides 1-29.

 

[PSEPK]

cal91... here is the Link for the wind guide you are asking for.

A good structural engineer is often a blessing for others.

 

[SteelSlugged]

Next time I will use a spoon to feed you.

Seriously, the wind guide has the information you are looking for.

Cal91, I believe the design guides you are referencing are the AISC design guides, are they not? If they are, don't forget about design guide 30 (sound isolation)!

PSEPK provided the link to the guide I was speaking of by ASCE. "Wind Loads: Guide to the Wind Load Provisions of ASCE 7-10". It teaches you how to use each wind code provision by in-depth examples.

The building frequencies change as buildings get taller, which in turn affects your gust effect factor. Therefore, the wind pressure at 50 ft will be different for a 50 ft building will be different for a 100 ft building will be different for a 1,000 ft building. Also, the code permits different methods for buildings less than 60ft, between 60ft and 160ft (maybe that number is wrong), and buildings greater than 60ft. A 10 story building may have different methodology in determining its response to wind forces.

 

[cal91]

Yes, I was mixed up AISC with ASCE :/

 

[firstoption]

Next time I will use a spoon to feed you. rednose

i'll take you up on that offer lol


Just looking confirmation, the "tributary area" that most plans show are essentially the "effective area" for the fasteners? (This is for C&C loads)

thanks

 

[calvinandhobbes10]

Yes.
Make sure the trib you pick is smaller or equal to the actual fastener trib. For fasteners it will almost certainly be the 10SF value.
Also, check whether the pressures specified are ULTIMATE (ASCE 7-10) or SERVICE (ASCE7-05). Most fastener designs or load charts still use SERVICE, even though the code has been updated and most structural designs reflect this. If unclear contact the engineer who wrote the plans.

 

[firstoption]

Yes.
Make sure the trib you pick is smaller or equal to the actual fastener trib. For fasteners it will almost certainly be the 10SF value.
Also, check whether the pressures specified are ULTIMATE (ASCE 7-10) or SERVICE (ASCE7-05). Most fastener designs or load charts still use SERVICE, even though the code has been updated and most structural designs reflect this. If unclear contact the engineer who wrote the plans.

ugh
this is why i hate checking others' work. There is always a screw up that they've always done wrong and expect me to just sign off.
Always much more time consuming for me than it was intended

 

[spats]

There is another design guide document that is even better than the ASCE guide. The name is "Design of Buildings for Wind", by Emil Simiu.