LDSS Light Diaphragm Spline Strap
The LDSS light diaphragm spline strap is designed to be placed directly on top of CLT (cross-laminated timber) and other mass timber panels to connect them together. Unlike plywood splines, the LDSS does not require routing. As part of the Simpson Strong-Tie® complete LDSS spline solution, the steel strap installs easily and safely using our PRO300SG2 Quik Drive® tool and collated Strong-Drive® WSV Subfloor screws. The LDSS features an innovative embossed hole design that helps guide the installation tool and increase fastener capacity.
- No routing required; the strap can be placed directly on top of mass timber panels, reducing manufacturing time and cost
- Less susceptible to moisture damage than plywood splines, reducing need for expensive repairs
- Embossed hole helps guide the installation tool into the hold and increases capacity per fastener
- Tested for in-plane shear values
- Can be used as part of a complete spline solution throughout a project for faster installation and to save on the total cost of spline connections
- Place the strap on the surface of the panels with the centerline notches aligned with joint between adjacent panels.
- From a standing position, hold tool perpendicular to the face of the strap and place the noseclip over the embossed feature. Drive the screw. Repeat.
- Use all specified fasteners.
Product Information Table
|Model No.||Ga.||Coating/Material||Packaging Qty.|
|LDSS48||18||Zinc Galvanized, G90||1|
|Model No.||Ga.||CLT Layup (min.)||Fasteners||Fastener Spacing (in.)||Allowable Shear Load (lb./ft.)||Slip Modulus Y(lb./in.)|
|LDSS48||18||Three-ply||#9 x 3" WSV||4||1,030||1,030||1,030||1,030||6,330|
|0.148 x 2 1/2"||4||430||430||430||430||7,685|
- Allowable loads are based on the use of cross-laminated timber (CLT) grades E1-E4 and V1-V4 material conforming to APA PRG-320.
- Allowable loads have been increased for wind or seismic loading with no further increase allowed; reduce where other loads govern.
- Allowable loads are based on lesser of calculations per SDPWS 2021 or assembly tests with a safety factor.
- Fastener failure modes are Mode IIIs or Mode IV.
- Nails: 0.148" x 2 1/2" = Nail dimension listed diameter by length; Screws: #9 x 3" WSV = model WSV3S.
- CLT panel minimum thickness is: three-ply = 4.125".
- The component of diaphragm deflection due to fastener slip at panel-to-panel joints calculated as δf = CLen, where,
C = (1/PL+1/Pw)/2
PL = Length of individual CLT panel (ft.) Pw = Width of individual CLT panel (ft.)
L = Overall length of diaphragm (ft.)
en = Design load per fastener (lb.) / Slip Modulus, Y(lb./in.)
(Reference — Applied Technology Council. 1981. Guidelines for the design of horizontal wood diaphragms. Redwood City, CA.)
For additional information on fastener slip and stiffness/slip modulus, see:
- American Wood Council. 2018. ANSI/AWC National Design Specification for Wood Construction, NDS®, Section 11.3.6. AWC, Leesburg, VA.
- Zhan, J.J. 1991. Design Equation for Multiple-Fastener Wood Connections. US Forest Service, Forest Products Laboratory, Madison, WI.
Code Reports & Compliance