AMENDMENTS TO THE BOCA NATIONAL BUILDING CODE/1996

CHAPTER 16 - STRUCTURAL LOADS

(Amd) 1608.3 Ground snow loads: Ground snow loads to be utilized in determining the design snow loads for roofs shall be as listed in Appendix A.

(Del) Figures 1608.3(1); Figure 1608.3(2); and Figure 1608.3(3): Delete figures and substitute with: Ground snow loads to be utilized in determining the design snow loads for roofs shall be as listed in Appendix A.

(Amd) 1608.4 Flat roof and low-slope snow loads: The snow load on unobstructed flat roofs and roofs having a slope of 30 degrees (0.52 rad) or less (P_f) shall be calculated in pounds per square foot using the following formula:

P_f = C_e I P_g

where:

C_e = Snow exposure factor determined from Table 1608.4.

I = Snow load importance factor determined from Note 1 to Appendix A

P_g = Ground snow load expressed in pounds per square foot as listed in Appendix A.

The calculated value of P_f shall not be less than 30 pounds per square foot. The 30 pounds per square foot minimum value of P_f shall also be applicable to sloped roof snow loads calculated in accordance with Section 1608.5. The calculated value of P_f without the 30 pounds per square foot minimum requirement shall be used to determine unbalanced snow loads, snow drifting loads and snow sliding loads in accordance with Sections 1608.6, 1608.7 and 1608.8.

Exception: The flat roof snow load on continuously heated greenhouses shall be calculated using the following formula:

P_f = C_tg C_e I P_g

where the thermal factor for greenhouses (C_tg) = 0.83

(Amd) 1609.1 General: All buildings, other exposed structures, components, cladding and roof coverings shall be designed to resist the pressures caused by wind in any direction as provided for herein, or shall comply with Section 6 of ASCE 7 listed in Chapter 35 using the Basic Wind Speeds for the 169 municipalities as listed in Appendix A. Where the provisions of ASCE 7 listed in Chapter 35 are utilized, the provisions of Section 1609.1.4 shall apply. The basic wind speed shall be determined in accordance with Section 1609.3. The exposure category shall be determined in accordance with Section 1609.4. The importance factor and minimum design wind load shall be determined in accordance with Sections 1609.5 and 1609.6. Wind loads on the building’s main windforce-resisting system shall be determined in accordance with Section 1609.7. Building component and cladding wind loads shall be determined in accordance with Section 1609.8. Wind loads on structures other than buildings shall be determined in accordance with Section 1609.9. Roof overhangs shall be designed for wind loads in accordance with Section 1609.10. Radio and television towers shall be designed for wind loads in accordance with Section 3108.4.

(Amd) 1609.3 Basic Wind Speed: The basic wind speed, in miles per hour, for the design of a structure shall be based on the location of the structure as listed in Appendix A. Reductions in the basic wind speed due to direct shielding afforded by adjacent buildings, structures or terrain features shall not be permitted.

(Del) Figure 1609.3: Delete figure and substitute with: The basic wind speed, in miles per hour, for the design of a structure shall be based on the location of the structure as listed in Appendix A.

(Del) Table 1609.3: Delete without substitution.

(Amd) 1609.5 Importance factor: Buildings and other structures shall be assigned a wind load importance factor (I) in accordance with Appendix A.

(Del) Table 1609.5: Delete table and substitute with: Wind load importance factors shall be as listed in Appendix A. Snow load importance factors shall be in accordance with Note 1 to Appendix A.

(Amd) Table 1609.7(6)

FOR BUILDINGS ^a,b,c,d,e(Gc_pi)

Note a. Values are to be utilized with the provisions of Sections 1609.7 and 1609.8.

Note b. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively.

Note c. To ascertain the critical load requirements for the appropriate condition, two cases shall be considered: a positive value of Gc_pi applied simultaneously to all surfaces and a negative value of Gc_pi applied to all surfaces.

Note d. Percentages of openings in a wall or roof surface are determined by the ratio of area of openings to gross area for the wall or roof surface considered.

Note e. Openings include permanent openings and those openings which are not designed to resist wind-borne debris or are not specifically protected from wind-borne debris impact where the ASCE 7- 95 basic wind speed is 110 miles per hour or greater, as listed in Appendix A.

(Amd) 1610.1.3 Seismic ground acceleration: The effective peak velocity-related acceleration (A_v) and the effective peak acceleration (A_a) shall be determined from Appendix A.

(Del) Figure 1610.1.3(1) and Figure 1610.1.3(2): Delete without substitution.

(Amd) 1610.4.1 Seismic base shear: The seismic base shear (V) in a given direction shall be determined in accordance with the following formula:

V = C_sW

where:

C_s = The seismic design coefficient determined in accordance with Section 1610.4.1.1.

W = The total dead load and applicable portions of other loads listed below:

1. For occupancies in Use Group S, a minimum of 25 percent of the floor live load shall be applicable.

Exception: Floor live load in public garages and open parking structures is not applicable.

2. Where an allowance for partition load is included in the floor load design, the actual partition weight or a minimum weight of 10 pounds per square foot of floor area, whichever is greater, shall be applicable.

3. Total operating weight of permanent equipment.

4. Snow load reductions of 80 percent are permitted.