Problem #5:

GIVEN: Bend Senior High School in Bend, Oregon. Assume that it has an ordinary flat

roof with roof drainage not constrained (roof is able to drain).

FIND:

Design snow load for the roof (psf).

Notes:

• Determine latitude/longitude of this location using Google Maps or Google Earth, for

example.

• Snow loads are determined using Section 1608 of the 2019 OSsc.

• Information from the Snow Load Analysis for Oregon published by the Structural

Engineers Association of Oregon can be obtained from:

snowload.seao.org/lookup.html You need to cut and paste the address into your

browser.

• Obtain the design ground snow load from this site. Note that the longitude must be in

negative degrees.

• The Importance Factor for Snow Load, Is=1.10, as found in ASCE 7-16 Table 1.5-2.

A secondary school is in Risk Category III (from OSSC Table 1604.5) if the (Group E)

occupancy load is greater than 250. Sisters HS has approximately 550 students and

faculty and staff.

• For flat roofs, the design snow load (on the roof) is given by:

a) Hibbeler Equation (1-5) (this is Eq. 7.3-1 in ASCE 7-16)

b) C₂ = 0.9 (fully exposed roof in surface roughness B- urban area with numerous

closely spaced obstructions) (Table 7.3-1 in ASCE 7-16).

c) C₁ = 1.0 for heated building (Table 7.3-2 in ASCE 7-16)

Also, read the Map Usage Notes (in the SEAO snow load site given above) on

Minimum Roof Design Snow Load and apply these as well. If the minimum is greater

than the value from Hibbeler Equation (1-5) (this is Eq. 7.3-1 in ASCE 7-16), then the

minimum applies. Lastly, include the rain-on-snow surcharge load if appropriate. Fully.

explain your logic in considering it.