Code of Massachusetts Regulations › 780 CMR - STATE BOARD OF BUILDING REGULATIONS AND STANDARDS › Chapter 16 - Structural Design › Section 1609 - WIND LOADS › Subsection 1609.1 - Applications

Current through Register 1525, July 5, 2024
Buildings, structures and parts thereof shall be designed to
				  withstand the minimum wind loads prescribed herein. Decreases in wind loads
				  shall not be made for the effect of shielding by other structures.
1609.1.1
Determination of wind
				loads.
Wind loads on every building or structure shall be determined in
				accordance with Chapter 6 of ASCE 7 or provisions of the alternate all-heights
				method in Section 1609.6. The type of opening protection required, the basic
				wind speed and the exposure category for a site is permitted to be determined
				in accordance with Section 1609 or ASCE 7. Wind shall be assumed to come from
				any horizontal direction and wind pressures shall be assumed to act normal to
				the surface considered.
Exceptions:
1. Subject to the limitations of Section
				1609.1.1.1, the provisions of ICC 600 shall be permitted for applicable Group
				R-2 and R-3 buildings.
2. Subject
				to the limitations of Section 1609.1.1.1, residential structures using the
				provisions of the AF & PA WFCM.
3. Subject to the limitations of Section
				1609.1.1.1, residential structures using the provisions of AISI S230.
4. Designs using NAAMM FP 1001.
5. Designs using TIA-222 for
				antenna-supporting structures and antennas.
6. Wind tunnel tests in accordance with
				Section 6.6 of ASCE 7, subject to the limitations in Section
				1609.1.1.2.
1609.1.1.1
Applicability.
The provisions of ICC 600 are applicable only to
				buildings located within Exposure B or C as defined in Section 1609.4. The
				provisions of ICC 600, AF & PA WFCM and AISI S230 shall not apply to
				buildings sited on the upper half of an isolated hill, ridge or escarpment
				meeting the following conditions:
1. The hill,
				ridge or escarpment is 60 feet (18 288 mm) or higher if located in Exposure B
				or 30 feet (9144 mm) or higher if located in Exposure C;
2. The maximum average slope of the hill
				exceeds 10 percent; and
3. The
				hill, ridge or escarpment is unobstructed upwind by other such topographic
				features for a distance from the high point of 50 times the height of the hill
				or 1 mile (1.61 km), whichever is greater.
1609.1.1.2
Wind tunnel test
				limitations.
The lower limit on pressures for main wind-force-resisting
				systems and components and cladding shall be in accordance with Sections
				1609.1.1.2.1 and 1609.1.1.2.2.
1609.1.1.2.1
Lower limits on main wind-force-resisting system.
Base
				overturning moments determined from wind tunnel testing shall be limited to not
				less than 80 percent of the design base overturning moments determined in
				accordance with Section 6.5 of ASCE 7, unless specific testing is performed
				that demonstrates it is the aerodynamic coefficient of the building, rather
				than shielding from other structures, that is responsible for the lower values.
				The 80-percent limit shall be permitted to be adjusted by the ratio of the
				frame load at critical wind directions as determined from wind tunnel testing
				without specific adjacent buildings, but including appropriate upwind
				roughness, to that determined in Section 6.5 of ASCE 7.
1609.1.1.2.2
Lower limits on components
				and cladding.
The design pressures for components and cladding on walls
				or roofs shall be selected as the greater of the wind tunnel test results or 80
				percent of the pressure obtained for Zone 4 for walls and Zone 1 for roofs as
				determined in Section 6.5 of ASCE 7, unless specific testing is performed that
				demonstrates it is the aerodynamic coefficient of the building, rather than
				shielding from nearby structures, that is responsible for the lower values.
				Alternatively, limited tests at a few wind directions without specific adjacent
				buildings, but in the presence of an appropriate upwind roughness, shall be
				permitted to be used to demonstrate that the lower pressures are due to the
				shape of the building and not to shielding.