Wind loads

Wind pressures on an enclosed or partially enclosed rigid building to ASCE 7-22: the velocity pressure (Chapter 26), the main wind force resisting system (MWFRS) by the directional procedure (Chapter 27, Part 1) with level forces, base shear and overturning, and components and cladding (C&C) for buildings with h ≤ 60 ft (Chapter 30, Part 1). The results are service-level (strength-level wind, ASCE 7-22 uses W directly in the load combinations); copy them into the member calculations as load type W.

Inputs of the wind loads #

• Wind speed and site: the basic wind speed V for the building's risk category (Fig. 26.5-1 or the ASCE Hazard Tool; the risk category is recorded and selects the map you read V from), the exposure category B, C or D (26.7, the engineer's judgment of the upwind terrain), the ground elevation factor Ke (Table 26.9-1 from the ground elevation, or Ke = 1.0, which is always permitted) and the directionality factor Kd (Table 26.6-1, 0.85 for buildings).
• Topography: Kzt entered (1.0 on flat terrain) or computed by 26.8 for a 2-D ridge, a 2-D escarpment or a 3-D axisymmetric hill from H, Lh and the distance x from the crest (negative upwind, positive downwind), with the Fig. 26.8-1 equations and the K1/(H/Lh) of the chosen exposure (26.8.2 permits the equations for increased accuracy; the tabulated K1 of the figure are the Exposure C values). ASCE 7-22 26.8.1 has three conditions: condition 1 (the building is in the upper half of a hill or ridge or near the crest of an escarpment, as shown in Fig. 26.8-1) is a check box for the engineer; conditions 2 and 3 (H/Lh ≥ 0.2; H ≥ 15 ft, 60 ft in Exposure B) are checked by the program. Where they are not met, Kzt = 1.0.
• Building: the enclosure classification (GCpi ±0.18 for enclosed and partially open, ±0.55 for partially enclosed, Table 26.13-1), the roof (flat, gable, hip), the plan length along the ridge and width across it, the eave height and the roof slope θ in degrees. The mean roof height is h = eave + rise / 2, except that the eave height is used for θ ≤ 10° (notation of Figs. 27.3-1 and 30.3-1 to 30.3-2G). The natural frequency n1 states that the building is rigid (n1 ≥ 1 Hz, 26.2; approximate values in 26.11.3). G is 0.85 or computed by 26.11.4.
• Levels: the floor and roof heights. Each level takes the wall load between the mid-heights of the stories next to it; the top level also takes the wall above it and the horizontal component of the roof pressures. The lower half of the first story goes directly to the foundation (it is part of the base shear).
• Components and cladding: one row per element: surface (wall or roof), zone and effective wind area A (span × the larger of the width and span/3, 26.2). Walls use zones 4 and 5 (Fig. 30.3-1). Roofs with θ ≤ 7° use zones 1′, 1, 2 and 3 (Fig. 30.3-2A); gable roofs above 7° use zones 1, 2 and 3 of Figs. 30.3-2B (7° to 20°), 2C (20° to 27°) and 2D (27° to 45°), hip roofs those of Figs. 30.3-2E (7° to 20°), 2F (20° to 27°) and 2G (45°), with the note 6 linear interpolation between 2F and 2G for 27° to 45°. ASCE 7-22 has no zones 2e, 2n, 2r, 3e, 3r on these figures (they were 7-16 zones); a row with such a zone, or a roof above 45°, needs GCp+ and GCp− entered. Entered values override the figure for any row. Parapet ≥ 3 ft (θ ≤ 7°): Fig. 30.3-2A note 5, zone 3 suction taken as zone 2 and the positive GCp of zones 2 and 3 as wall zones 4 and 5 (the wall values of Fig. 30.3-1 without the note 5 reduction).

Checks performed #

The drawings (on screen, in the report and as a PDF / DXF sheet) show the building section in each wind direction (wind from the left) with the external MWFRS pressures as bands whose depth shows the value: the windward wall by height, the leeward wall, and the roof surfaces or the roof zones from the windward edge with both Cp cases; the heights are dimensioned to scale, and a building longer than the sheet holds at 1/16" = 1'-0" is compressed along its length and marked NTS. When wall components were entered, a wall elevation shows the C&C zones 4 and 5 with the width a and their design pressures. The sheet notes give qh, the internal pressure to add, the side-wall pressure and the roof C&C pressures; the roof C&C zone extents, the load cases 2 to 4 of Fig. 27.3-8 and the lateral system are not part of the calculation and are not drawn. The level forces and base shears are in the results.

Limitations #

• Not covered (reported as not feasible): open buildings, flexible buildings (n1 < 1 Hz), roof slopes of 90°, C&C for h > 60 ft (Ch. 30 Part 2), roof C&C above 45° or in zones the 7-22 figures do not have, without entered GCp.
• Not covered and not checked: the envelope procedure (Ch. 28), other structures and building appurtenances (Ch. 29: rooftop equipment, signs, solar panels), parapet loads (27.3.4, 30.8) and roof overhangs (30.7), monoslope, stepped, multispan, mansard and domed roofs, tornado loads (Ch. 32), the reduction factor Ri for large partially enclosed buildings (Ri = 1.0 is used, conservative), the note-b area reduction of the −1.3 roof Cp of Fig. 27.3-1 (not applied, conservative), qi = qz at the highest opening of a partially enclosed building (qh is used, which 27.3.1 permits as conservative), the exception of Fig. 27.3-1 note 6 for moment-frame roofs (the roof horizontal component is never taken below zero).
• Kz is computed with the note 1 formula of Table 26.10-1, which the code permits; the table's rounded values differ by up to 1.5 % (Exposure B at 30 ft: 0.689 against 0.70).
• Above 45° the Fig. 27.3-1 roof Cp is the single positive value (0.6 at 60°, 0.01θ to 80°, 0.8 above) with the note 2 zero for the negative case.
• A hip roof uses the Fig. 27.3-1 gable values with the parallel-to-ridge Cp on the hip ends, and the roof widths of the hip geometry for the horizontal component.
• Every table, equation and figure was checked against the printed ASCE/SEI 7-22 (Tables 26.6-1, 26.9-1, 26.10-1, 26.11-1, 26.13-1; 26.8, 26.10, 26.11.4, 27.1.5, 27.3.1, 27.3.5, 30.2.2, 30.3.2; Figs. 26.8-1, 27.3-1, 27.3-8, 30.3-1 and 30.3-2A to 2G read from the page images). No item is left to verify.

Verification examples #

Values from the standard (ASCE/SEI 7-22; pages of the PDF on file):

Published worked examples of the directional procedure to ASCE 7-22 (AISC Design Examples v16.0, Part III building; WoodWorks five-story-over-podium design example, 2nd ed., 2025):

The examples' parapet pressures (27.3.4) are not compared (parapets are outside this calculation). No published C&C worked example to ASCE 7-22 is on file (the ASCE wind loads guide remains on the documents list); C&C is checked against the figure values above and by hand. Hand calculations in closed form: