Loads

ASCE/SEI 7-10, Minimum Design Loads of Buildings and Other Structures, lists two methods for calculating wind pressures: Main Wind Force Resisting System (MWFRS) and Components & Cladding (C&C). This report will provide information to assist the building designer in deciding upon the appropriate analysis method for uplift due to wind loading.

A lay-on gable frame is typically connected from the top during truss placement, but after sheathing is installed, this connection is no longer visible for the building inspector to verify. This creates a need for an alternate connection that is visible from below. The goal of this Research Report is to analyze a simple, cost-effective, toe nail connection between the lay-on gable frames and supporting truss system that is visible after sheathing is installed.

The prescriptive residential energy code requirements found in the 2009, 2012 and 2015 International Residential Code (IRC) include requirements for continuous insulation at foundations in several climate zones. This Research Report discusses the issue of cantilevered sill plates supporting metal plate connected wood trusses installed parallel and perpendicular to the foundation walls where there is a potential for discontinuous planes between the exterior wall above the sill plate and the foundation insulation planes. 

Explore the two different methods used to calculate a wall panel’s capacity to resist applied lateral loads.

Editor’s Note: The purpose of this article series is to identify truss-related structural issues sometimes missed due to the day-in and day-out demands of truss design/production and the fragmented building design review and approval process. This series will explore issues in the building market that are not normally focused upon, and provide recommended best-practice guidance.

Learn more about a future industry testing concept for the SBC Research Institute.

Consider for a moment the basics of manufacturing a truss. Based on SBCA’s 2012 Financial Performance Survey, lumber accounts for roughly 40 percent of the total cost. Plates account for about eight percent of the total cost. Design and production labor account for 30 percent, and delivery, sales and overhead account for the remaining 22 percent (these are rough industry averages). All other things being equal, if you could decrease your lumber costs by a few percentage points while raising your plate costs a small amount, would you take the trade-off?

Building Designers need to account for the dead and live loads of fire sprinkler systems, in addition to the other load requirements imposed under the model building codes. Truss Designers are responsible for incorporating the additional load from the fire sprinkler systems into the truss design. The information in this Research Report is applicable to both floor and roof systems. Only vertical loads from fire sprinkler systems are discussed; lateral loads, where required, should be evaluated separately by a Registered Design Professional. 

Truss industry standard of care items are contained throughout ANSI/TPI 1,* The National Standard for Metal Plate Connected Wood Truss Construction. The focus of this article is ANSI/TPI 1 Chapter 2, Section 2.3.5.1 and companion Section 2.4.5.1, which require a truss designer to prepare truss design drawings (TDD) based on design criteria and requirements set forth in the construction documents. The truss industry should expect to get this information from the building designer (BD), which may include the building owner, contractor or a registered design professional (RDP). Particularly when there is an RDP for the building, the design community expects the truss industry to design components that conform to the truss framing plan and specified design parameters within the construction documents, unless instructed otherwise in writing.

 
  • Even with its many benefits, innovative framing faces resistance. Prescriptive codes don’t directly promote innovative framing, and markets are slow to adopt for many reasons.
  • The earlier in the process CMs can get in front of building designers, the greater their ability to influence the use of innovative framing techniques to design buildable structural framing. 
  • In order to get innovative framing ideas into the market effectively, you need to have your ducks in a row prior to approaching the building designer.