General Requirements¶

The General Requirements section holds the Chapter 26 parameters the wind calculations in the module share: the basic wind speed, the exposure, the topographic factor, the ground elevation factor (ASCE 7-16 and 7-22), the gust effect factor, and the enclosure classification. Set them first; the MWFRS and components and cladding sections read them. Components and cladding and the envelope procedure do not use the gust effect factor, because their combined coefficients GCp and GCpf already include it (Section 26.11.7; Section 26.9.7 in ASCE 7-10).

Section, table, and figure numbers in the text are the ASCE 7-16 and 7-22 numbers unless another edition is named. ASCE 7-10 numbers Chapter 26 differently from Section 26.9 on; the Code Reference table gives the numbers for each edition.

Key Features¶

• Basic wind speed for the structure's risk category, with the ASCE Hazard Tool a click away
• Ground surface roughness and exposure category, for the whole site or by direction
• Topographic factor Kzt, ground elevation factor Ke (ASCE 7-16 and 7-22), and the gust effect factor G
• Enclosure classification with the internal pressure coefficient GCpi that follows from it
• A summary with the code section beside every value

Basic Wind Speed¶

The ASCE Hazard Tool button opens ascehazardtool.org in a second window. Enter the speed here when you have it.

Exposure Category¶

With one exposure, the summary shows it for all four quadrants. With the per-direction switch on, each quadrant gets its own pair of inputs, and the MWFRS pressures use the exposure of the wind direction being calculated.

ASCE 7 permits exposure by wind direction only for the Chapter 27 directional procedure on enclosed and partially enclosed buildings (Section 26.7.4.1). The envelope procedure, open buildings with free roofs, and components and cladding use the exposure that results in the highest wind loads (Sections 26.7.4.1, 26.7.4.2, and 26.7.4.4).

Topographic Factor¶

Topographic factor, Kzt required stays off for a site on level ground, and Kzt is 1.0. Switch it on for a building on or near a hill, ridge, or escarpment that meets the conditions of Section 26.8.1, and describe the feature in the inputs that appear. The factor is calculated per Figure 26.8-1 and applied at every height.

Ground Elevation Factor¶

Include ground elevation factor, Ke adjusts the velocity pressure for the air density at the site's elevation per Section 26.9. Switch it on and enter the Ground elevation from sea level in feet; Ke is calculated from Table 26.9-1. Leave it off to use Ke = 1.0, which is permitted and conservative. The ground elevation factor exists in ASCE 7-16 and 7-22 only; ASCE 7-10 has no Ke, and its velocity pressure equation does not include one.

Building Flexibility¶

Building classified as flexible stays off for a rigid building, one with a fundamental frequency of 1 Hz or more. The Gust Factor for rigid buildings, G is then 0.85, the value Section 26.11.1 permits for a rigid building. Switch it on for a flexible building to enter the properties Section 26.11.5 needs for the gust effect factor Gf. In ASCE 7-10 these are Sections 26.9.1 and 26.9.5.

Enclosure Classification¶

Choose the classification per Section 26.12 (Section 26.10 in ASCE 7-10), from the openings in the walls and roof. The Internal Pressure Coefficient, GCpi fills in from Table 26.13-1 (Table 26.11-1 in ASCE 7-10) and is used by both the MWFRS and the components and cladding sections. ASCE 7-10 has no partially open classification; a building that meets neither the open nor the partially enclosed definition is enclosed.

Summary View¶

The summary on the right lists every general parameter with its section reference, the roughness and exposure by quadrant, the factors, and the enclosure classification with GCpi. The MWFRS and components and cladding sections add their own results below it.

Next Steps¶

Add an MWFRS Directional section for the main wind force resisting system, and a Components & Cladding section for the elements.

Code Reference¶