ASCE 7-22 Wind: MWFRS Design Pressure for Residential Gable Roof (Chapter 28 Envelope)

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ASCE 7-22 Wind: MWFRS Design Pressure for Residential Gable Roof (Chapter 28 Envelope)

Summary: Calculate design wind pressure for Main Wind Force Resisting System on a residential gable roof per ASCE 7-22 Chapter 28 (Envelope Procedure), including…

Overview

Building / scenario

  • Occupancy / use: Residential, Risk Category II
  • Geometry / size: 40 ft × 28 ft, h = 20 ft, 6:12 roof
  • Site / exposure: ASCE 7-22

Problem statement

A Risk Category II single-family home is 40 ft × 28 ft in plan with 20 ft mean roof height, 6:12 roof slope. Basic wind speed 115 mph, Exposure B. The building is enclosed and qualifies as low-rise for Chapter 28. Determine MWFRS design pressures for roof and wall zones per ASCE 7-22 Chapter 28 Section 28.3.1 and evaluate minimum design wind loads per Section 27.1.5 and Section 28.3.6.

Workflow in StructSuite

Select Chapter 28 — Envelope Procedure at the top of the wind module. Enter Risk Category II, V = 115 mph, Exposure B, K_d = 0.85, K_zt = 1.0, K_e = 1.0, enclosed, GC_pi = 0.18. Step 4: h = 20 ft, Kh from Table 26.10-1; after Step 6, Step 4 shows Roof angle = 6:12 = 26.57° (or θ = 26.6° in degrees mode). Step 5: qh. Step 6: L = 40 ft, B = 28 ft, gable roof, θ = 26.6° (6:12), Figure 28.3-1 GC_pf zones. Step 7: p = qh×K_d×[(GC_pf)−(GC_pi)] for each zone and load case; review Minimum Design Wind Loads and governing base shear comparison.

Design considerations (excerpt)

Residential Risk II. 115 mph inland; 130–150 mph coastal. q ∝ V²: 30% speed increase = 70% pressure increase. Hurricane clips, straps sized from zone pressures. Address or zip for ASCE 7 Figure 26.5-1.

Step 4: h = 20 ft drives Kh; Step 6: 40×28 ft plan, gable θ = 6:12. After θ is entered, Step 4 accordion shows Roof angle = rise:run = degrees. Zone size a = 0.1×least plan dimension per Table 28.2-1.

B typical suburban. C (open lot, new development): 25–35% higher. Enclosed: GC_pi=±0.18. Partial enclosure (garage door open): higher internal pressure. Kzt for hillside—ridge sites can double wind.

qh is used in Equation 28.3-1. Step 7 zone uplift drives roof-to-wall connections; Minimum…

Related terms

  • StructSuite
  • structural engineering
  • design example
  • wind
  • ASCE 7-22
  • MWFRS
  • residential gable mwfrs

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