TPI Initiative

Improve Efficiency in Floor Truss Design

The use of floor trusses in the marketplace is generally low in comparison to other engineered products. The various projects being explored under this initiative are looking for methods to enhance, if possible, the efficiencies in floor truss design making them more economical or competitive with other engineered products used in floor construction. Projects underway are in the following areas:

Top-Chord Bearing Improvements

  • Provide a methodology to determine, by calculation, the reaction limit for a Top-Chord Bearing MPC wood truss. The methodology will be able to be used in lieu of the currently published prescriptive maximum reaction limits and will take advantage of the effects of lumber size, lumber grade, lumber species, plate size and will not be limited to predetermined geometric configurations as is the current practice.

  • This methodology will be for use by truss engineers and truss software developers who desire to provide an alternate solution beyond the current ANSI/TPI 1 prescriptive tables.

Use of Composite Action Design Concepts

  • Provide a methodology to consider the benefits of composite action provided by structural sheathing attached to metal plate connected (MPC) wood floor trusses. When sheathing specifications are included on the Truss Design, this design method could be used to enhance the design stiffness and strength of a given MPC wood floor truss which in turn may provide a more economical floor truss solution.

  • This methodology will be for use by truss engineers and truss software developers who desire to provide an alternate solution beyond the current ANSI/TPI 1 provisions.

Treatment of Open Chases in MPC Floor Truss Design

  • Metal plate connected (MPC) floor trusses with open chases are generally subject to critical load cases (unbalanced load checks) which could require larger connector plates and higher-grade lumber than the full-span live load condition. TPI engineers are researching this unbalanced load check that is commonly done for MPC floor truss design and seeing if any adjustments might be warranted to the current practice. TPI engineers are also looking into ways truss designers can more efficiently design floor trusses. In the case of floor trusses with open chases, adding a diagonal web in the chase opening that is not being used can be a quick way to improve design efficiency that could lead to reductions in the lumber grades or adjustments in plate sizes thereby producing a more economical floor truss solution.

  • These design tips and clarifications are intended for use by truss designers who desire to provide the most efficient floor truss designs.

What are the next steps?

Drafts of the methodology are currently being researched and developed by TPI member companies. Once drafts have been prepared there may be a need for additional review and comments from others prior to finalizing. If you are interested in being considered as a reviewer or just want to be kept informed of the progress just let us know by clicking on the button below. Once signed up and as the initiative gets underway TPI will contact you with further information on this initiative.

Related Links

Cross Platform Communication Initiative - improve cross platform communication & collaboration between software & machinery

TPI 1 Maintenance Initiative - maintain the metal plate connected wood truss industry as a viable, credible, & safe engineering solution based on sound engineering principles

TPI Initiative Question & Comment Form