×
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

Tributary are of a window with a semicircular top.

Tributary are of a window with a semicircular top.

Tributary are of a window with a semicircular top.

(OP)
I could use some help resolving the tributary area of a 48" wide window that is 126" in height. If the window were rectangular I would not have a problem but the top of window is a semicircle. Any help would be appreciated as I am determining the anchor locations at the window frame to the framing.

I did a crude sketch of the window and want to know if I have the tributary area of the semicircle correct.

Thanks
Vinny

RE: Tributary are of a window with a semicircular top.

Not sure what code you're working with, but your window area as shown is 40.3 square feet.  If you considered it as full rectangle, it would be 42 square feet.  Not enough difference to worry about on the tributary area scale.

Your perimeter is 27.28 ft.  

Your question is confusing.  If you are considering fastener loading, the tributary area is for 1 fastener, so the maximum coefficients apply.  

Please clarify your question and why you need to separate the tributary area of the arch from the remainder.

RE: Tributary are of a window with a semicircular top.

(OP)
The loading at the sill is traianglar and the loading on a rectangular window is trapezoidal. How does the round window resolve its forces at the frame. I take the wind pressure times the area and resolve those forces to pound/inch so I know how to size the anchor clips.

RE: Tributary are of a window with a semicircular top.

Agree with Ron, you are over-thinking it. Any quick trib area assumption you make should not make a difference in the sizing and spacing of the fasteners. Never cut it close on window and door fasteners, these can cause the whole structure to fail if they blow in.

RE: Tributary are of a window with a semicircular top.

(OP)
Both of you guys are right and I so use a 300 % safety factor but I am still trying to just understand how the pressure in the circular portion transmits to the window frame.  

RE: Tributary are of a window with a semicircular top.

Assume the pressure acting on the window, in this case negatively, creates a uniform perimeter load around the window, normal to the substrate, without regard to its shape.

By the way, I typically use a safety factor of 4 for component and cladding fasteners in direct tension.

The distribution you are trying to apply is more applicable to the glass than to the frame.  The load is applied to the glass by the wind, which in turn is transmitted to the frame by shear at the edge of the glass.  To try to evaluate small variations in the stress distribution in the class is a waste of time.

RE: Tributary are of a window with a semicircular top.

(OP)
Ron

So, you propose that I take the entire area of the window and multiply it by the factored pressure, take that load and add safety factor of 400% then take the load and divide it by the permiter to determine the loading per inch. Then size my anchors and clip assemblies appropriately?

I will use the square approach and use 42 SF as the area. The windload used in this example is 30 PSF and the safety factor is 4. Thereforer the loading from the entire window is 5,040 lbs. Using the permiter of 31.28-feet. The loading of about 161 lb/ft of the window frame.

Would that be the way that you safely compute the loads at the ourside of the window?

Thanks
Vinny

RE: Tributary are of a window with a semicircular top.

Vinny, it doesn't make any difference to the final numbers, but if your calcs will be reviewed by someone (structural engineer of record, building department, etc.), apply the factor of safety  to the fastener>> (other side of the equation).

That way, it will be apparent to whomever reviews, that your are applying the factor of safety to the resistance, not to the load.  If you are using manufacturer's fastener pullout tables, make sure they are given in ultimate load, not allowable load.  If allowable load, you don't have to apply the FS=4, but it would be a good idea to determine if their factor of safety is 4.

RE: Tributary are of a window with a semicircular top.

Windload = 2*30 = 60 plf on each jamb.  If fastener spacing = s then load per fastener = 60s.  Factored resistance required per fastener = 4*60*s (using Ron's FS).

Maintain the same spacing around the curve, i.e. s.

BA

RE: Tributary are of a window with a semicircular top.

(OP)
Thanks guys!

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