1609.3 Ultimate Design Wind Speed

The ultimate design wind speed, V_ult, in mph, for the determination of the wind loads shall be determined by Figures 1609.3(1), 1609.3(2) and 1609.3(3). The ultimate design wind speed, V_ult, for use in the design of Risk Category II buildings and structures shall be obtained from Figure 1609.3(1). The ultimate design wind speed, V_ult, for use in the design of Risk Category III and IV buildings and structures shall be obtained from Figure 1609.3(2). The ultimate design wind speed, V_ult, for use in the design of Risk Category I buildings and structures shall be obtained from Figure 1609.3(3). The ultimate design wind speed, V_ult, for the special wind regions indicated near mountainous terrain and near gorges shall be in accordance with local jurisdiction requirements. The ultimate design wind speeds, V_ult, determined by the local jurisdiction shall be in accordance with Section 26.5.1 of ASCE 7.

In nonhurricane-prone regions, when the ultimate design wind speed, V_ult, is estimated from regional climatic data, the ultimate design wind speed, V_ult, shall be determined in accordance with Section 26.5.3 of ASCE 7.



FIGURE 1609.3(1) ULTIMATE DESIGN WIND SPEEDS, v_ult, FOR RISK CATEGORY II BUILDINGS AND OTHER STRUCTURES



FIGURE 1609.3(2) ULTIMATE DESIGN WIND SPEEDS, v_ult, FOR RISK CATEGORY III AND IV BUILDINGS AND OTHER STRUCTURES



FIGURE 1609.3(3) ULTIMATE DESIGN WIND SPEEDS, v_ult, FOR RISK CATEGORY I BUILDINGS AND OTHER STRUCTURES

When required, the ultimate design wind speeds of Figures 1609.3(1), 1609.3(2) and 1609.3(3) shall be converted to nominal design wind speeds, V_asd, using Table 1609.3.1 or Equation 16-33.



where:

Vasd	=	Nominal design wind speed applicable to methods specified in Exceptions 4 and 5 of Section 1609.1.1.
Vult	=	Ultimate design wind speeds determined from Figures 1609.3(1), 1609.3(2) or 1609.3(3).

TABLE 1609.3.1
WIND SPEED CONVERSIONS^{a, b, c}

Vult	100	110	120	130	140	150	160	170	180	190	200
Vasd	78	85	93	101	108	116	124	132	139	147	155

For SI: 1 mile per hour = 0.44 m/s.

1. Linear interpolation is permitted.
2. V_asd = nominal design wind speed applicable to methods specified in Exceptions 1 through 5 of Section 1609.1.1.
3. V_ult = ultimate design wind speeds determined from Figure 1609.3(1), 1609.3(2) or 1609.3(3).