The following is an example of how pre-engineered runs are specified from this catalogue.
The Designer shall determine the cumulative overturning tension and compression forces at each floor. The ATS components (Strong-Rod™ threaded rod and bearing plates) are selected on the basis of the factored tension forces. The designer should then select the lumber at the ends of the shearwall on the basis of the factored forces. Note that the compression forces are typically greater than the tension forces due to combinations of additional forces such as dead and live load.
The Designer is responsible for evaluating the effects of lumber shrinkage and ATS elongation on shearwall drift. Please refer to page 16 of the catalogue for information regarding shearwall drift.
For simplicity of the design and installation, it is recommended that the Designer group similar runs together.
Determine the cumulative overturning and incremental forces based on the applied storey shear:
The moment arm is the distance between the centerline of compression members and centerline of tension members. For symmetrical post configurations, this is typically the distance between tension rods on each end of the shearwall. For tension loads, gravity loads have not been included.
T3 = Cumulative OT Tension L3 = 15(3) = 12.30kN 3.66
T2 = Cumulative OT Tension L2 = 15(6) + 12.5(3) = 34.84kN 3.66
T1 = Cumulative OT Tension L1 = 15(9) + 12.5(6) + 3(10) = 65.57kN 3.66
Determine the incremental overturning forces at each level. These are typically the difference in the cumulative forces at the stories above and below. These forces are generated at each level, and are transferred into the rod by the bearing plate and nut.
Incremental OT Force roof = 12.30kN Incremental OT Force L3 = 34.84 − 12.3 = 22.54kN Incremental OT Force L2 = 65.57 − 34.84 = 30.73kN Figure 2 below shows the load path at level 2.
Determine the cumulative compression forces in the studs at the end of the shearwalls. P = Forces due to gravity loads. Cumulative OT Compression L1 = T1 + 5 + 10 + 10 = 90.57 kN Cumulative OT Compression L2 = T2 + 5 + 10 = 49.84 kN Cumulative OT Compression L3 = T3 + 5 = 17.30 kN
Select system and verify tension capacities
Try: TDS3-7/8 (see page 50 of the catalogue)STEP 3
Select compression members (see pages 33-37 of the catalogue)
For the top floor, assume Designer opts to use bridge block termination with a single 2x4 cripple stud and a single 2x4 king stud on either side.STEP 4
For worst-case scenarios (where compressive load nears compressive resistance of studs), see page 38 of the catalogue.STEP 5
Total vertical displacement of each storey, or between restraints, meets the total vertical displacement limit of 0.30" or 7.6 mm because the pre-engineered run TDS3- 7/8 uses regular-strength rod. As discussed on page 16 of the catalogue, the prescriptive limit can be waived if the building design conforms to the calculation procedures in CSA O86-14 Engineering Design in Wood (Clause 11.7.1), APEGBC Technical and Practice Bulletin, or the Mid-Rise Wood- Frame Construction Handbook Special Publication SP-57E by FPInnovations.