Building Design and Construction Handbook - Merritt - Ventech!

PROTECTION AGAINST HAZARDS 3.5
FIGURE 3.1 Effects of wind on a low building with pitched roof. (a) Airflow at the building. (b)
Wind applies inward pressure against the windward wall, suction on the leeward wall, and uplift
over all of a roof with slight slopes. (c) With a steep roof, inward pressure acts on the windward
side of the roof and uplift only on the leeward side. (d) Pressure distribution along walls and roof
assumed for design of wind bracing of a building.
3. Instruments used should have response characteristics consistent with the required
accuracy of measurements to be recorded.
4. Account should be taken of the dependence of forces and pressures on the
Reynolds number of the air motion.
5. Tests for determining the dynamic response of a structure should be conducted
on a model scaled with respect to dimensions, mass distribution, stiffness, and
damping of the proposed structure.
In the analytical methods specified by building codes, maximum wind speeds
observed in a region are converted to velocity pressures. These are then multiplied
by various factors, to take into account building, site, and wind characteristics, to
obtain design static wind loads. Bear in mind, however, that, in general, code requirements
are applicable to pressures considerably smaller than those created by
tornadoes, which may have wind speeds up to 600 mi/hr. For more information on
wind loads, see Art. 5.1.2.
3.2.3 Failure Modes
Consideration of the ways in which winds may damage or destroy buildings suggests
provisions that should be made to prevent failures. Past experience with build-