In this article, we follow up on our April 17 webinar, Meeting Braced-Wall Requirements: A New Portal Frame Solution, by answering some of the interesting questions raised by attendees.
During the webinar, we discussed how the Strong-Wall site-built portal frame system (PFS) provides designers, builders and contractors in prescriptive jurisdictions with a new alternative to IRC wall-bracing methods. In case you weren’t able to join our discussion, you can watch the on-demand webinar and earn PDHs and CEUs here.
As with our previous webinars, we ended with a Q&A session for the attendees. Bryan Wert, our Engineering Manager in the Southeast US, and Tom McClain, our Strong-Wall Shearwalls senior product manager, answered as many questions as they had time ford. Now we’re back to recap our answers to some of the more popular questions. If you’d like to see the full list of questions and answers, though, click here.
Design
Can the PFS be used for engineered design in seismic design categories D or E?
The PFS is applicable for use in Wind and SDC A, B and C for detached one- and two-family dwellings. At this time, we haven’t yet evaluated the PFS solution for high-seismic conditions. Designs in SDC D0-D2 should consider using one of our prefabricated Steel Strong-Wall® shearwalls (SSW) or Strong-Wall® wood shearwalls (WSW).
Are there actual lateral load capacities available for the PFS?
The PFS is designed for the prescriptive market. We will not be publishing allowable shear loads at this time; just equivalent braced wall lengths.
Can you use 1 1/2″-thick LVL for the PFS?
Yes. You would need to shim out at the holdown (or full height) similar to sawn lumber. The capacity would be based on Douglas fir / southern pine.
Is there a code report?
No. We will be pursuing a code report for IRC bracing applications. Our current WSW and SSW Strong-Wall® code reports, ICC-ES ESR-2652 and ICC-ES ESR-1679 respectively, are recognized for use in IBC engineered designs.
Anchorage
Can SET-XP® be used instead of SET-3G™?
Yes, SET-XP is an approved alternative. However, since SET-3G is the superior product (by all reports), our recommendation is to use that.
Can the PFS be used on a CMU foundation?
It could, but we haven’t developed the anchorage solutions yet. CMU anchorage solutions are currently being developed. They will probably involve a cast-in-place solution and require anchoring into the footing. This is in the works for 2019.
Is there a cast-in-place anchorage solution for the PFS?
CIP anchorage solutions are currently being developed. We hope to have those available by the end of the year.
General Wall Bracing
Are these just for garage openings?
No, they could be used in any portal application. For example, large picture windows, a sliding glass door or similar openings in other parts of the structure.
How does the PFS compare to the APA PFH?
Width: We are narrower. 9 1/4″ to 11 7/8″ vs. 16″
Installation: The PFS is easy to execute and much more likely to be installed properly.
Cost: Using sawn lumber makes the material costs about equal. How much margin our distributors add will influence the final overall cost, but we’ll be pretty close. Definitely a lot less than using prefabricated shearwalls.
Performance: The equivalent braced wall length varies by size and framing materials, but we’re comparable.
Framing
Can holes be drilled in the columns?
We allow for drilling a 7/8″-diameter hole along the vertical centerline of the column, in the allowable hole zone. From 3″ down from the top to 14″ up from the bottom. This is shown in the installation instructions and structural detail PFS1 on our website (strongtie.com/pfs). A “pancake” (flat) electrical box, of the same thickness as the siding, could be cut into the siding for this application.
Can the PFS be used on a wood beam or raised-floor system?
For now, our anchorage is designed around retrofitting with either SET-3G™ or AT-XP® adhesives into prepoured concrete, so we don’t have anything currently developed for that.
Do the columns and beams have to be made of the same material?
No. Using the same material is the simplest configuration, and the easiest to frame; but you could use sawn lumber columns (with a shim) and LVL headers to minimize cost. See page four of our flier (F-L-PFS19) or the structural drawings for details.
Do portal frames come in greater widths to accommodate 2×6 exterior wall framing?
The portal frame system is designed for use in 2×4 framing. Designs that require 2×6 framing due to loading should consider specifying one of our prefabricated SSW or WSW Strong-Wall® shearwalls. For more information, visit Strong-Wall Shearwalls.
Software
I’m not getting PFS as a solution when I input my job criteria in the bracing selector. How do I make it show up as a solution?
You have to use one of the “height to underside of top plates” choices under the 1st Story Wall Height pulldown menu. The other choices of “with header on top” are unique to WSW or SSW Strong-Wall panels and won’t result in a PFS selection.
The complete list of questions and answers is posted online.
The article, “Questions Answered: Strong-Wall® Site-Built Portal Frame System,” appeared first on the Simpson Strong-Tie Structural Engineering Blog. To sign-up to receive the Engineering Blog in your inbox, go to seblog.strongtie.com/subscribe.
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