Question

Problem #6:

GIVEN: One-story fire station planned near Florence, Oregon with a flat roof. Roof

height = 12 ft. This critical facility is in Risk Category IV (from OSSC Table 1604.5).

The building is rectangular and 50 ft. x 100 ft. in plan. It is situated right next to the

beach, and the 100 ft dimension is parallel to the coast. It is considered to be enclosed

per ASCE 7-16 Section 26.2.

FIND: The controlling wind design pressures (combining external and internal

pressures) to be used for the windward wall.

These should be pressures for design of the main wind-force-resisting system

(MWFRS) and not for the components and cladding. The MWFRS is composed of the

walls and roof as they resist the wind as a complete structural system. Components

and cladding are parts of the walls and roof as they resist the wind locally.

SOLUTION NOTES:

1) Section 1609 of the 2019 OSSC covers wind loadings. It will be used in combination

with appropriate sections in ASCE 7-16 that are briefly discussed in the Hibbeler text.

The necessary information from ASCE 7-16 will be provided here.

Individual MIV Set (Loadings): STRUCTURAL THEO (C6_381_001_F2022)

2) Use the 2019 OSSC to determine the Basic Design Wind Speed, V, for this location.

3) The Directional Procedure for MWFRS in an enclosed building is outlined in ASCE

7-16 Table 27.2-1. The definition of an enclosed building is provided in ASCE 7-16

Sections 26.2 and 26.12.

4) Velocity pressure exposure coefficient Kz = 1.03 for Exposure D (Table 26.10.1 in

ASCE 7-16) for z ≤ 15 ft. Directionality factor, Kg = 0.85 (Table 26.6-1 in ASCE 7-16-

note that this is different from the Hibbeler text). Topographic factor, Kat= 1.0 for flat

terrain (ASCE 7-16 Section 26.8.2). Ground elevation factor, Ke=1.0 for sea level and

to be conservative for all elevations. Gust effect factor, G=0.85 for rigid buildings and

other structures.

5) Internal pressure coefficient for enclosed building is from ASCE 7-16 Table 26.13-1

or from the Hibbeler text.

6) Velocity pressure exposure coefficient, K₂ is from Table 28.10-1 in ASCE 7-16 or

from wall pressure coefficient in Hibbeler.

7) Velocity Pressure qz or qn is from Eq. 28.10-1 in ASCE 7-16 or from the Hibbler text.

8) External pressure coefficient, Cp is from Fig. 27.3-1 in ASCE 7-18 or from the

Hibbeler text.

9) Design wind pressure on the wall is given by Eq. 27.3-1 for a rigid building in ASCE

7-16 or in the Hibbeler text.