Example
A Risk Category II warehouse is 100 ft long by 80 ft wide with a flat roof and mean roof height h = 28 ft. A large roll-up door on one long wall can create a partially enclosed condition. Ultimate design wind speed V = 115 mph, Exposure C, K_d = 0.85, K_e = 1.0, K_zt = 1.0. The building is classified as partially enclosed per Section 26.12; use GC_pi = ±0.55 per Table 26.13-1. For Chapter 27 Section 27.3.1, take the height of the highest opening for positive internal pressure as z = 22 ft above ground (typical large door head height). Use z = 28 ft for windward wall q_z for the windward surface at full height unless a smaller controlling strip is specified. Determine MWFRS design pressures using the Directional Procedure.
How StructSuite solves this
Select Chapter 27. Enter Risk Category II, V = 115 mph, Exposure C, K_d = 0.85, K_zt = 1.0, K_e = 1.0. Set enclosure to partially enclosed and GC_pi = 0.55. Enter 100 ft × 80 ft plan, h = 28 ft, flat roof, θ = 0°. In Step 6 Chapter 27 inputs, enter height of highest opening z = 22 ft and windward reference z = 28 ft as applicable. Complete Step 7 for governing pressures.
Steps
- Wind MWFRS procedure: Chapter 27 (Directional)
Design consideration: Warehouses with large doors are often partially enclosed or require a rational analysis when the door is open; the selected classification must match the load case in the permit set. Chapter 27 Section 27.3.1 uses q_z at the height of the highest opening for positive internal pressure when partially enclosed—this can significantly increase net pressure on the roof and leeward wall compared to enclosed.
In StructSuite: At the top of the wind module, above Step 1, select the Chapter 27 — Wind Loads on Buildings: Main Wind Force Resisting System (Directional Procedure) radio button (not Chapter 28 Envelope Procedure). This example uses ASCE 7-22 Chapter 27 §27.3.1 and Figure 27.3-1 for MWFRS pressures.
- Step 1: Determine risk category of building
Design consideration: 115 mph with partially enclosed GC_pi amplifies net pressure changes versus ±0.18. Door and opening schedules should be consistent with the classification stated in the wind load calculation.
In StructSuite: In Step 1, use the Risk Category dropdown to select I, II, III, or IV (e.g., II for offices, residential). In the Basic Wind Speed (mph) input box enter 115. Per ASCE 7-22 §26.2, Figure 26.5-1. If using address lookup, use the address search to auto-fill wind speed.
- Step 4: Velocity pressure exposure coefficient
Design consideration: Flat roof and long span diaphragms: large plan dimensions increase total shear to the lateral system. Mean roof height 28 ft drives K_z in Exposure C; confirm door opening height and mean roof height are consistent with the architectural sections.
In StructSuite: In the Building dimensions section, in Building Length (ft) enter 100; in Building Width (ft) enter 80; in Mean Roof Height (ft) enter 28. These drive Kh from ASCE 7-22 Table 26.10-1.
- Step 3: Wind load parameters
Design consideration: Exposure C with K_zt = 1.0 assumes flat terrain; confirm no escarpment within the approach distance. If K_zt > 1.0, velocity pressure increases at the site.
In StructSuite: In Step 3, use the Exposure dropdown to select B, C, or D. If ground elevation > 1000 ft, use Table 26.9-1 for Ke. For topographic features (hills, ridges), use the Kzt section and enter parameters from ASCE 7-22 Figure 26.8-1. Kd = 0.85 for MWFRS is typical.
- Step 5: Velocity pressure at mean roof height
Design consideration: Chapter 27 uses q_z at discrete heights; for partially enclosed internal pressure, the q at the height of the highest opening is critical. Compare Step 5 tabulated q_z at z = 22 ft and z = 28 ft to the values used in Step 7.
In StructSuite: In Step 5, verify velocity pressure at mean roof height and, for Chapter 27, the listed q_z at each height z (ft) per ASCE 7-22 Table 26.10-1 and Equation 26.10-1. For this example, mean roof height is 28 ft and basic wind speed V is 115 mph.
- Step 6: External pressure coefficients
Design consideration: Enter the height of the highest opening (ft) and windward z (ft) in the Chapter 27 Step 6 inputs so internal pressure uses the correct q. Review wall and roof C_p for both orthogonal directions; large doors can change which wall is critical for shear and torsion.
In StructSuite: In Step 6, confirm Building Length (ft) 100, Building Width (ft) 80, Mean Roof Height (ft) 28, roof type Flat, and roof angle 0.0 degrees. For Chapter 27, review Figure 27.3-1 external pressure coefficients C_p for each orthogonal wind direction (Part 1 and Part 2). If the building is partially enclosed, enter the height z for windward q_z (ft) and the height of the highest opening (ft) where shown for Section 27.3.1 internal pressure.
- Step 7: Design wind pressures
Design consideration: Partially enclosed cases often govern net uplift and lateral load on the MWFRS. Check both positive and negative external pressure with ±GC_pi. Use governing pressures for connections, bracing, and foundation overturning; document assumptions in the calculation package.
In StructSuite: In Step 7, review the Chapter 27 design wind pressure table per ASCE 7-22 Section 27.3.1. Use governing surface pressures for MWFRS load combinations; account for both positive and negative external pressure with internal pressure (GC_pi) from Step 3.
Live design (pre-filled)
The form below is the real StructSuite module with example data loaded. Display only—values cannot be changed.
Steps to Determine Wind Loads on MWFRS
ASCE 7-22 Tables 27.2-1, 28.2-1
User Note: Use Chapter 27 to determine wind pressures on the MWFRS of buildings with any general plan shape, building height, or roof geometry that matches the figures provided. These provisions use the traditional "all heights" method (Directional Procedure) by calculating wind pressures using specific wind pressure equations applicable to each building surface.
User Note: Use Chapter 28 to determine the wind pressure on the MWFRS of low-rise buildings that have a flat, gable, or hip roof. These provisions use the Envelope Procedure by calculating wind pressures from the specific equation applicable to each building surface. For building shapes and heights for which these provisions are applicable, this method generally yields the lowest wind pressure of all the analytical methods specified in this standard.