Approach

These requirements are based primarily on the American Iron and Steel Institute’s (AISI) Specification for the Design of Cold-Formed Steel Structural Members [1] for steel member strength, on the American Concrete Institutes’s (ACI) Building Code Requirements for Structural Concrete [2], on the Structural  Design of Insulating Concrete Form Walls in Residential Construction [3] for concrete design and specification, and on the Standard for Cold-Formed Steel Framing - Prescriptive Method for One and Two Family Dwellings [29] for steel framing requirements. The provisions for building loads are based on the American Society of Civil Engineers’ (ASCE) Minimum Design Loads for Buildings and Other Structures [4], the International Building Code [5], and the International Residential Code [6].

These provisions are intended to represent sound engineering and construction practice, taking into account the need for practical and affordable construction techniques for residential buildings. This document is not intended to restrict the use of sound judgment or exact engineering analysis of specific applications.

Scope

The provisions of this Prescriptive Method apply to the construction of detached one- and two- family dwellings, townhouses, and other attached single-familydwellings in compliance with the general limitations of Table 2.1. The limitations are intended to define the appropriate use of this document for most one- and two- family dwellings. Using insulating concrete forms and cold-formed steel systems with other construction materials in a single structure shall be in accordance with the applicable building code requirements for that material, the general limitations of Table 2.1, and relevant provisions of this document. An engineered design shall be required for applications that do not meet the limitations of Table 2.1.

The provisions of the Prescriptive Method shall not apply to irregular structures or portions of structures in Seismic Design Categories C, D , and D . Only such irregular

portions of structures shall be designed in accordance with accepted engineering practice to the extent such irregular features affect the performance of the structure. A portion of the building shall be considered to be irregular when one or more of the following conditions occur:

• Exterior shear wall lines are not in one plane vertically from the foundation to the uppermost story in which they are required (i.e., cantilevers).
• A section of floor or roof is not laterally supported by shear walls on all edges.
• An opening in the floor or roof exceeds the lesser of 12 ft (3.7 m) or 50 percent of the least floor dimension.
• Portions of the floor are vertically offset.
• Shear walls (i.e. exterior ICF walls) do not occur in two perpendicular directions.
• Shear walls are constructed of dissimilar systems on any one story level.

Foundation Wall:  The structural element of a foundation that transmits the load of a structure to the earth; includes basement, stem, and crawlspace walls.

Slab-on-Grade:  A concrete floor, which is supported by, or rests on, the soil directly below.

Slump:  A measure of consistency of freshly mixed concrete equal to the amount that a cone of uncured concrete sags below the mold height after the cone-shaped mold is removed in accordance with ASTM C 143 [9].

Smoke-Development Rating:  The combustibility of a material that contributes to fire impact through life hazard and property damage by producing smoke and toxic gases; refer to ASTM E 84 [10].

Span:  The clear horizontal distance between bearing supports.

Stem Wall:  A below-grade foundation wall supported directly by the soil or on a footing. Wall thickness and height are determined as that which can adequately distribute the building loads safely to the earth.

Stirrup: Steel bars, wires, or welded wire fabric located perpendicular to horizontal reinforcement and extending across the depth of the member in concrete beams, lintels, or similar members subject to large shear loads.

Story: That portion of the building included between the upper surface of any floor and the upper surface of the floor next above, except that the top-most story shall be that habitable portion of a building included between the upper surface of the top-most floor and the ceiling or roof above.

Story Above-Grade: Any story with its finished floor surface entirely above grade except that a basement shall be considered as a story above-grade when the finished surface of the floor above the basement is (a) more than 6 feet (1.8 m) above the grade plane, (b) more than 6 feet (1.8 m) above the finished ground level for more than 50 percent of the total building perimeter, or (c) more than 12 feet (3.7 m) above the finished ground level at any point.

Strap:  Flat or coiled sheet steel material typically used for bracing and blocking which transfers loads by tension and/or shear.

Stud: Vertical structural element of a wall assembly, which supports vertical loads and/or transfers lateral loads.

Townhouse: Attached single-family dwelling units constructed in a row with each unit separated by fire walls at property lines.

Track:  A framing member consisting of only a web and two (2) flanges. Track depth measurements are taken to the inside of the flanges.

Truss:  A coplanar system of structural members joined together at their ends usually to construct a series of triangles that form a stable beam-like framework.

Vertical Reinforcement:  Steel reinforcement placed vertically in concrete walls to strengthen the wall against lateral forces and eccentric loads. In certain circumstances, vertical reinforcement is required for additional strength around openings.

Waffle-Grid Wall: A solid concrete wall with closely spaced vertical and horizontal concrete members (cores) with a concrete web between the members created by the ICF form; refer to Figure 2.1. The thicker vertical and horizontal concrete cores and the thinner concrete webs create the appearance of a breakfast waffle. It is also referred to as an uninterrupted-grid wall in other publications.

Wall Height: The clear vertical distance between the finished floor and the finished ceiling. Where a finished floor does not exist (i.e., crawlspace), the wall height is the clear vertical distance between the interior finish grade and the finished ceiling.

Walls (steel):

Structural or Load Bearing:  Wall systems subject to loads that exceed the limits for a non-structural system.

Non-Structural or Non-Load Bearing:  Wall systems that are limited to a lateral (transverse) load of not more than 5 psf (240 Pa), a superimposed vertical load per member, exclusive of sheathing materials, of not more than

100 lb/ft (1460 N/m), or a superimposed vertical load per member of not more than 200 lbs (890 N).

Web: That portion of a framing member that connects the flanges.

Web Crippling: The localized permanent (inelastic) deformation of the web member subjected to concentrated load or reaction at bearing supports.

Web Stiffener: Additional material that is attached to the web to strengthen the member against web crippling. Also called a bearing stiffener.

Wind Exposure: refer to Exposure Categories.

Wind Load: The force or pressure exerted on a building structure and its components resulting from wind. Wind loads are typically measured in pounds per square foot (psf) or Pascals (Pa).

Wind Speed: Wind speed is the design wind speed related to winds that are expected to be exceeded once every 50 years at a given site (i.e., 50 year-return period). Wind speeds in this document are given in units of miles per hour (mph) by “3- second gust” measurements (refer to Table 2.2 to convert to fastest-mile wind speed).

TABLE 2.2

EQUIVALENT BASIC WIND SPEEDS (mph)1

For SI: 1 mph = 1.609 km/hr = 0.447 m/sec

1 Linear interpolation is permitted.

Yield Strength: A characteristic of the basic strength of the steel material defined as the highest unit stress that the material can endure before permanent deformation occurs as measured by a tensile test in accordance with ASTM A 370 [11].