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Component Manufacturing dverti$ dverti $ er
By Paul McEntee
Don’t Forget! You Saw it in the
January 2024 #16294 Page #100
Adverti$$er
Developing High-Capacity Tension Straps for Mass Timber Engineering
ass timber buildings use cross-laminated timber (CLT) or mass plywood panels to create horizontal diaphragms to transfer wind and seismic forces into the vertical elements of the lateral-force-resisting system. Spline connections resist shear forces at the panel joints, which I discussed in Mass Timber Diaphragm Options with Four Different Connection Types — How Our LDSS48 Light Diaphragm. I wanted to discuss several options for tension straps used for chord splices and collector forces. This article will not discuss methods for calculating design forces. Instead, I am going to focus on several strap products and how we developed their allowable loads.
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Straight straps are one of the few connector products where allowable loads are based on calculations, not testing. For joist hangers, hurricane ties, or holdowns, there are all sorts of eccentricity that create shear, prying, and withdrawal forces on the fasteners and difficult-to-predict load distribution in the connector. Straight straps don’t have any of that, so we can calculate the steel tension capacity and the fastener capacity per code. However, Simpson Strong-Tie has tested many of our straps because we really love testing. We also receive questions sometimes about deflection or whether or not you can install a given strap over plywood (you can, as long as you use nails 2½” or longer). The need for larger force capacity became apparent as Simpson Strong-Tie began entering the structural steel market. We had stretched the limits of the existing equipment when we had to figure out how to use two of the 55 kip (55,000 lb) actuators together to push and pull on a Yield-Link® Moment Frame with a 36”-deep beam. To go even bigger for subsequent test programs with larger capacities, we needed to contract with university labs. Now, with the added capabilities of our Million Pound Rig, we’ll be able to support our growing market areas in structural steel, mass timber, and concrete strengthening. CS14 Test Setup Continued next page
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