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) and h > 60 ft (Part 2). The enclosure is entered or classified from the opening areas (26.12). Signs, rooftop equipment, chimneys, tanks and towers are the Wind on other structures calculation (Chapter 29). 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), entered or classified from the openings: the opening areas of each long wall, each end wall and the roof (doors, vents and windows that may be open in a design storm, Commentary C26.12); the gross areas follow from the building (end walls with the gable triangle, the roof surface). Each wall is taken in turn as the wall receiving positive pressure (26.12.2): open where Ao ≥ 0.8Ag; partially enclosed where Ao > 1.1Aoi, Ao > min(0.01Ag, 4 ft²) and Aoi/Agi ≤ 0.20; enclosed where every wall has Ao ≤ min(0.01Ag, 4 ft²) and Aoi/Agi ≤ 0.20 (the Table 26.13-1 criterion; the 26.2 definition omits the ratio); otherwise partially open; a building both open and partially enclosed is partially open (26.12.1). An open building is not feasible. Single unpartitioned large volume: a partially enclosed building may use GCpi × Ri, Ri = 0.5 (1 + 1/√(1 + Vi/(22,800 Aog))) ≤ 1.0 (Eq. 26.13-1), with Vi entered or the building volume and Aog the total openings (needs the opening areas). 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). h > 60 ft (Part 2, Eq. 30.4-1, Fig. 30.4-1): walls zones 4 and 5 (a = 10 % of the least width, ≥ 3 ft), positive pressure with qz at the component's height z (column Height z; blank = h) and suction with qh, qi = qh; roofs up to 7° zones 1, 2 and 3 (no positive roof curve is given; with a parapet ≥ 3 ft zone 3 is treated as zone 2, note 7); steeper roofs use the Part 1 roof figures with qh (note 6). The 30.4 exception (60 ft < h < 90 ft and h ≤ the least width: Part 1 figures permitted) is a check box.

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 (entered or classified), flexible buildings (n1 < 1 Hz), roof slopes of 90°, roof C&C above 45° or in zones the 7-22 figures do not have, without entered GCp, the Part 1 exception outside 60 ft < h < 90 ft and h ≤ the least width.
• Not covered and not checked: the envelope procedure (Ch. 28), other structures and building appurtenances (Ch. 29: the Wind on other structures calculation; solar panels), parapet loads (27.3.4, 30.8) and roof overhangs (30.7), elevated buildings' bottom surfaces (30.3.2.1, 30.4.2.1), qz at the highest opening for the positive internal pressure of a partially enclosed building (qh, permitted as conservative), monoslope, stepped, multispan, mansard and domed roofs, tornado loads (Ch. 32), the reduction factor Ri for large partially enclosed buildings when not chosen (Ri = 1.0, 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 #

Verification status: 171 values compared in 30 examples (20 published, 10 hand calculations from the cited equations): 170 within tolerance, 1 recorded deviations. Code basis: the provisions it uses were read in the target edition.

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:

Wave 6 additions (C&C for h > 60 ft, enclosure from the openings):