Risk II → (I = 1.0).
For simplicity, many users set I=1.0 for Risk Category II.
Interpolation: (K_z) for 30 ft ≈ 0.70.
) from the wind speed maps provided in ASCE 7-05 (Figure 6-1).
[ \textIf z \leq 15\ \textft: K_z = 2.01 \left( \frac15900 \right)^2/9.5 ] [ \textIf z > 15\ \textft: K_z = 2.01 \left( \fracz900 \right)^2/9.5 ]
Unlike modern ASCE 7 editions which use ultimate-strength (LRFD) wind speed maps, ASCE 7-05 uses . These values are obtained from the geographic wind speed map in Figure 6-1 of the standard. For most of the continental United States, the baseline wind speed is
q30=0.00256×0.98×0.85×12,100≈25.80 psfq sub 30 equals 0.00256 cross 0.98 cross 0.85 cross 12 comma 100 is approximately equal to 25.80 psf Step 2: Compute at roof height (assume for simplicity, so Step 3: Compute Design Pressure (
For , external pressure coefficients ( C_p ) are obtained from ASCE 7‑05 Figures 6‑6 (enclosed/partially enclosed buildings) and Figures 6‑6A through 6‑8 (low‑rise buildings). The pressure on each surface is calculated as:
Before diving into the equations, it is essential to understand the core structural classifications defined in ASCE 7-05:
Used for smaller elements like windows, doors, and roofing panels.
Used when the building does not qualify for Method 1 but does not require wind tunnel testing.
(Gust Effect Factor): For rigid structures (natural frequency can be taken as a fixed value of
Always distinguish between the Main Wind Force Resisting System (total loads) and Components & Cladding (local pressures, e.g., roof panels, window glass).
is the external pressure coefficient combined with local gust effects, derived directly from Figures 6-11 through 6-17 based on the element's effective wind area. 4. Summary Comparison: ASCE 7-05 vs. Later Editions
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