APA Designers Circle News & Features

Winter 2018

Highlights from this Month's e-Newsletter


Force Transfer Around Openings (FTAO)

New Test Results, New Tool



Force transfer around openings (FTAO) has distinct advantages as a shear wall analysis method: accommodating multiple openings, asymmetric wall piers, and typically requiring fewer hold-downs. But the FTAO method, compared to the code-allowed alternatives, could seem a rather involved and lengthy approach to shear wall analysis—until now. Designing with FTAO has become much more accessible with a game-changing FTAO methodology tool based on APA’s extensive full-scale wall modeling and testing. This tool, the APA FTAO Calculator, and its companion publication, Technical Note: Design for Force Transfer Around Openings, Form T555, were developed by APA to assist design professionals in solving for the required sheathing, nailing, hold-downs, straps, and maximum deflection.


FTAO Calculator

APA Force Transfer Around Openings (FTAO) Calculator: Automated Process for Calculating FTAO Design

The APA FTAO Calculator is a downloadable Excel worksheet that offers calculations for shear walls with one, two, and three openings, as well as a design example. With user inputs, the FTAO calculator will produce:

  • maximum shear force to determine sheathing and attachment
  • maximum hold-down force for overturning resistance
  • required corner force for the tension straps above and below openings when needed
  • maximum deflection of the wall system


Technical Note: Design for Force Transfer Around Openings, Form T555 T555

Structural engineers can employ a rational analysis to design shear walls with multiple, asymmetric openings based on the recent testing outlined in this publication. FTAO is a popular solution where walls have narrow piers, and it provides structural and nonstructural benefits, including reduced anchorage and added redundancy. FTAO’s incorporation of continuous wall sheathing also aids with cladding attachment and improves drainage and energy efficiency of the building.

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Inside the Circle

Meet the Research Team

APA has participated in force transfer around openings research since 2009, resulting in new tools for design professionals and engineers. Tom Skaggs, PhD, PE, led the FTAO research at APA. Skaggs, along with engineered wood specialists Karyn Beebe, PE, and Jared Hensley, PE, used the analysis of the data to create the worksheet-based Force Transfer Around Openings Calculator and its corresponding publication, Technical Note: Design for Force Transfer Around Openings (FTAO), Form T555. Skaggs was also responsible for the testing and analysis of the joint research project between Forest Products Laboratory/University of British Columbia and APA, as documented in Joint Research Report: Evaluation of Force Transfer Around Openings – Experimental and Analytical Studies, Form M410. The field services staff at APA is available to help designers understand FTAO and offer support for the new tools.


Tom Skaggs


Thomas D. Skaggs, PhD, PE, is the manager of product evaluation in APA–The Engineered Wood Association’s technical services division. During his 23 years at APA, he has been actively involved in dynamic testing of products, including vibration performance of I-joist floor systems and evaluating the cyclic performance of braced wall and shear wall assemblies. He was also involved in the design and implementation of APA’s full-size three-dimensional house testing program. Prior to joining APA, Skaggs’ research at Virginia Tech was in the area of metal-plate-connected wood trusses.

Outside the Circle