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StiffWall® Shear Wall System

TSN_StiffWall_Banner.jpg
 

TSN’s StiffWall® shear wall system is a stick build system designed to carry loads concentrically from the point of applied loads to the foundation or other termination point, that utilizes light gauge straps on both sides of the wall for shear resistance. StiffWall SWS consists of two Column/Boot Assemblies (at each end post) and Flat Strap (2 sides of X-bracing). StiffWall provides superior quality with high yield ASTM A1003 steel and hot-dipped galvanized coating for long-term durability.  The design is ideal for job specific sizes with established load requirements. The Steel Network has optimized the design and fabrication of StiffWall through a series of both component and full scale wall assembly tests, using state of the art technology to measure performance.

Quality:

  • Designed and manufactured to meet the performance requirements of the project.
  • Satisfies maximum story drift requirements per IBC.
  • Only mill certified high strength steel is used.
  • Exceeds industry standards for sizes and loads.
  • Tested for multi-story application and capable of carrying loads present in 10 story buildings.
  • Each component is selected to meet or exceed both strength and stiffness requirements of the applicable building code.
  • Allows 3 times the window space of plywood braced structures.

Value:

  • Templates are not required for hold-downs, eliminating unrealistic field procedures.
  • Plywood sheathing with fastener schedules and/or CMU shear walls are eliminated.
  • Inspection is limited to simple connections at corners.
  • Versatile design may be incorporated into steel, concrete and wood construction.
  • No welds or controlled inspections associated with welding.
  • Simplified anchoring system through floors and at roof termination.
  • The strap system is on the outside of the wall to facilitate electrical and pipe work in the wall cavity.
Downloads Download Technical data Tech Sheet | Download drawing file DWG | Download BIM data BIM |
Product Information
StiffWall® Column/Boot Assembly

StiffWall® Column/Boot Assembly (Load Bearing Member & Anchor)

StiffWall® Columns come with Boots preattached. Each Column is delivered fully assembled and ready for installation to the wall panels per project requirements, and is specified using simple nomenclature indicating only essential design requirements for each shear wall element.

StiffWall® Column/Boot Assembly Downloads: Download Technical data Tech Sheet | Download drawing file DWG | Download specification data Specs | Download BIM data BIM
 
 
StiffWall® Column

StiffWall® Column (Load Bearing Member)

StiffWall® Column is a component of TSN's StiffWall System, designed to carry loads concentrically from the point of applied loads to the foundation or other termination point and is designed to fit inside of TSN's StiffWall Boot Kit.

StiffWall® Column Downloads: Download Technical data Tech Sheet | Download specification data Specs | Download BIM data BIM
 
StiffWall® Boot

StiffWall® Boot (Anchor)

StiffWall® Boots provide the optimal cost-effective solution for shear wall connections. They are sized to fit inside standard track and are available for all standard sizes.

StiffWall® Boot Download: Download Technical data Tech Sheet | Download BIM data BIM
 
TightStrap®

Flat Strap (X-Bracing)

In addition to it's standard use in wall bridging, Flat strap is also the tension element used to transfer loads between diagonally located strap tracks in TSN's StiffWall® System.

Flat Strap Downloads: Download Technical data Tech Sheet | Download drawing file DWG | Download specification data Specs
 
TightStrap®

TightStrap® (Tensioning Tool)

TightStrap® is a unique device used to tension (tighten) flat strap in the field.

TightStrap® Download: Download Technical data Tech Sheet
TSN_StiffWall_Colors_with_Bridging

US Patent #'s 6,892,504 & 7,788,878

Column/Boot Assembly
SigmaStud and BuckleBridge
Flat Strap
StiffWall Shear Wall System
** StiffWall is embedded between studs and does not replace load bearing studs

StiffWall shear walls provide both lateral strength and stiffness. Lateral strength is needed to resist horizontal loads due to wind and earthquake forces. Properly designed and constructed shear walls transfer lateral forces to the next structural element in the load path below them, such as other shear walls, floors, or foundations.

Lateral stiffness is needed to prevent excessive side-sway of the structure. When shear walls are of adequate stiffness, they will maintain the lateral deflection or serviceability requirements of the building. In addition, buildings with sufficient lateral stiffness will suffer less nonstructural damage, further avoiding long-term degradation due to veneer cracking and water infiltration.

Shear_Wall_Lateral_Strength
Tracing and verifying load paths through a structure is crucial to protect engineering liability. Loads need to migrate from the roof, through the wall and floor systems, and terminate in the foundation. Shear wall systems transfer lateral loads from the member above (i.e. floor slab) to the member below (i.e. foundation). StiffWall® provides a traceable, easily verifiable load path through the structure.
 
Load Paths
  1. Load transfers from the floor above through the floor connector, and to the StiffWall Boot
  2. From the Boot to the Strap Track*
  3. From the Strap Track to the flat strap*
  4. Through the flat strap to the Strap Track at opposite corner*
  5. From the Strap Track to the Boot
  6. From the Boot to the floor/system or foundation below
* The column section assumes the compression loads.
* Uplift forces are transferred through the StiffWall® Boot through full bearing onto the SWS Boot Base Plate to the anchor.
TSN StiffWall Load Paths Close

Simple Steps to Design Shear Walls

The following steps offer a guide for the design of the StiffWall® shear wall system. In addition, SteelSmart® System software is available (at www.steelsmartsystem.com) to select the optimal column, boot, strap and fasteners used in the installation of StiffWall. Contact The Steel Network for additional design information.

Planning Shear Walls

To develop an efficient shear wall layout several factors need to be considered:

  • Height to Width aspect ratio guidelines should be observed in order to maximize effectiveness
  • Shear walls should be evenly distributed across the floor plan to reduce additional lateral loads resulting from torsional effects on the floor plan
  • Shear Walls located in load bearing walls may use floor dead loads with the appropriate load combination to offset uplift forces in the StiffWall
  • Walls must stack vertically from top floor of structure to anchorage point or foundation
  • Shear walls may overlap when the available wall space has been depleted

Step 1 - Select StiffWall® Column

This unique column contains an additional return lip to form a double lip, thus creating a stronger, more effective bearing section. The column is the main vertical load-bearing transfer element in StiffWall. The images at right show a typical StiffWall Column shape.

Important Note:

The StiffWall Boot must be used with the StiffWall Column. Standard stud (S) sections will not fit inside the StiffWall Boot or Strap Track.

TSN_SW_Column_Shape_Key_Horizontal

Step 2 - Select StiffWall® - Boot

The StiffWall Boot is a critical element enabling StiffWall to simultaneously resist higher loads and provide positive load transfer between elements, something conventional shear wall systems do not provide. Five different StiffWall Boots are available for accommodating changing loading requirements. Refer to the Boot Capacities table data to select the appropriate Boot to fit project conditions.

Step 3 - Determine Column-To-Boot Uplift Fastener Requirement

Attaching to the StiffWall Column with #12 screws or 0.5" A325 bolts, the boot enhances construction efficiency by reducing the number of installed fasteners used in conventional flat strap shear walls. For uplift conditions, calculate the number of screws for the Light and Plus Boots by dividing the total uplift force by the single screw shear. For Small, Medium, Transition, and Large Boots, refer to the chart below for the number of fasteners to the column.

Single Column Allowable Uplift Load (T2) (kips)
Column Thickness Light/Plus Boot Small Boot Medium / Transition Boot Large Boot
(1) #12 Screw 350, 362 & 400 550 & 600 800 350, 362 & 400 550 & 600 800 550 & 600 800 550 & 600 800 350, 362 & 400 550 & 600 800
(mils) (inch) (2) Bolts (4) Bolts (3) Bolts (4) Bolts (5) Bolts (6) Bolts (8) Bolts (10) Bolts (7) Bolts (14) Bolts
33 0.0346 0.27 1.71 3.43 3.43 2.57 3.43 4.13 5.14 5.14 6.85 6.85 7.50 8.56 5.27 9.78 11.30
43 0.0451 0.41 2.30 4.59 4.59 3.45 4.59 5.38 6.89 6.89 9.19 9.19 9.77 11.48 6.87 12.74 14.72
54 0.0566 0.57 2.97 5.94 5.94 4.46 5.94 6.75 8.91 8.91 11.88 11.88 12.26 14.75 8.62 15.99 18.48
68 0.0713 0.78 3.88 7.77 7.77 5.83 7.77 8.51 11.65 11.65 15.45 15.54 15.45 18.58 10.86 20.15 23.28
97 0.1017 0.78 5.96 11.92 11.92 8.94 11.92 12.13 17.88 17.88 22.04 23.84 22.04 26.50 15.48 28.73 33.20
118 0.1242 0.78 7.66 14.64 15.32 11.49 15.32 14.82 22.98 22.98 26.91 30.64 26.91 32.37 18.91 35.09 40.55
Single Column Allowable Uplift Load (T2) (kips)
Column Thickness Light/Plus Boot Small Boot Medium / Transition Boot Large Boot
(1) # 12 Screw 350, 362 & 400 550 & 600 800 350, 362 & 400 550 & 600 800 550 & 600 800 550 & 600 800 350, 362 & 400 550 & 600 800
(mils) (inch) 2) Bolts (4) Bolts (3) Bolts (4) Bolts (5) Bolts (6) Bolts (8) Bolts (10) Bolts (7) Bolts (14) Bolts
33 0.0346 N / A 3.43 6.85 6.85 5.14 6.85 8.26 10.28 10.28 13.70 13.70 14.99 17.13 10.54 19.55 22.59
43 0.0451 N / A 4.59 9.19 9.19 6.89 9.19 10.76 13.78 13.78 18.37 18.37 19.54 22.97 13.73 25.49 29.45
54 0.0566 N / A 5.94 11.88 11.88 8.91 11.88 13.51 17.82 17.82 23.77 23.77 24.53 29.50 17.23 31.98 36.96
68 0.0713 N / A 7.77 15.54 15.54 11.65 15.54 17.01 23.31 23.31 31.08 31.08 30.90 37.16 21.71 40.29 46.55
97 0.1017 N / A 10.60 21.21 21.21 15.90 21.21 24.27 31.81 31.81 42.41 42.41 44.07 53.00 30.97 57.47 66.40
118 0.1242 N / A 10.60 21.21 21.21 15.90 21.21 26.51 31.81 31.81 42.41 42.41 53.01 53.01 37.11 70.18 74.22

Table Notes

* Compression loads are transferred via full column bearing onto boot.

  • Bolts referenced in table are ASTM A325 bolts.
  • Refer to the Design Example for uplift requirements.
  • Allowable loads for screws are based on AISI S100-12 Specification, Section E4.3.
  • Maximum allowable load per (1) #12 screw in shear is equal to 0.849 kips, based on commercial screw data.
  • Allowable loads for bolts are based on AISI S100-12, Section E3.3.2.
  • Maximum allowable load per (1) A325 bolt in shear is equal to 4.42 kips, based on AISI S100-12, Section E3.4.

Step 4 - Select Stiffwall® - Flat Strap

Flat strap is the tension element used to transfer loads between diagonally located strap tracks. Flat strap selection is simplified to 6 strap types (see chart below), with load capacity factored using standard 12ga (97mils) strap track.

Strap Width Strap Thickness Yield Strength Recommended No.
of screws/row
Allowable Tension
in Single Strap
No. of #12
Screws for Max.
Strap Tension
(in) (mil) (ksi) (#) (kips) # (kips)
4 54 50 4 5.77 11 (6.26)
6 54 6 8.65 16 (9.10)
8 54 8 11.54 21 (11.95)
8 68 8 14.53 19 (14.76)
10 68 10 18.17 24 (18.65)
SW_Strap_Track_FS

It is recommended to limit the use of 10" flat strap to shear wall panels that have aspect ratio > 0.72:1 (36 degrees)

Step 5 - Condition 1: Anchor Design At Foundation

Refer to the Hilti North American Product Technical 2011 Edition Volume 2, page 160 to design anchors at the foundation. For typical details of StiffWall at foundation, see Example Details provided in this catalog. TSN recommends the use of a washer, lock washer, double-nut washer, or tack weld at each end of the bolt.

Allowable Tension and Shear Values of Hilti HIT-RE 500 Adhesive Anchors
Anchor Diameter Embedment Depth Yield Strength Shear (Non Seismic Design)
Based on Bond or Concrete Based on Steel Strength Based on Bond or Concrete Based on Steel Strength
f'c = 2,000 psi f'c = 4,000 psi ASTM A193 B7 f'c = 2,000 psi f'c = 4,000 psi ASTM A193 B7
(in) (in) (lb) (lb) (lb) (lb) (lb) (lb)
⅞" 4 3,005 5,300 24,805 7,795 11,020 12,780
7 ⅞ 12,495 14,815 17,175 24,290
10 ½ 14,705 15,345 26,440 37,390
1 ¼" 5⅝ 5,760 9,935 50,620 14,760 20,870 26,080
11 ¼ 24,610 31,620 35,050 49,570
Table Notes
  • Bond, concrete, and steel values are referenced from Hilti North American Product Technical Guide 2014 Edition Volume 2.
  • Apply influence factors for spacing and/or edge distance to concrete/bond values, then compare to the steel strength value. The lesser value is to be used for design.
  • Applied tension force shall include tension resulting from prying action produced by deformation of connected parts.
  • For design of anchorage under seismic conditions, refer to ACI 318 Appendix D - Anchoring to Concrete provisions.

Step 5 - Condition 2: Through Floor Fastener Connection

Refer to Section E3.4 in the AISI S100-12 to design through floor bolt fasteners. For typical details of StiffWall at top termination (roof) and through floors, see Example Details provided in the TSN Load Bearing Member Technical Catalog. TSN recommends use of a washer, lock washer, double-nut washer, or tack weld at each end of the bolt.

Fastening StiffWall® - Boot Through Floor
Shear Stress (Fv) for A325 Threads (ksi)
Shear Stress (Fv) for A325 Threads (ksi) Tension Stress (Ft) (ksi) Combined Shear (Fv) and Tension (Ft)
27.0 45.0 Section E3.4, AISI S100-12 Spec.
Important Notes
  • Ensure full bearing between through-floor bolts and the floor slab. Enlarged or notched bolt holes in the slab must be filled with grout.
  • Applied tension force shall include tension resulting from prying action produced by deformation of the connected parts.
  • The area of a ⅞" bolt = 0.60 in2 and area of 1 ¼" bolt = 1.23 in2.
  • Allowable Shear per one ⅞" A325 Bolt = 16.2 kips.
  • Allowable Shear per one 1 ¼" A325 Bolt = 33.2 kips.
  • Allowable Tension per one ⅞" A325 Bolt = 27.0 kips.
  • Allowable Tension per one 1 ¼" A325 Bolt = 55.4 kips.
  • Boot Base plate guide holes for wall widths less than 5.5" accommodate ⅞" through-rods for Light, Plus, Small, Medium, and Large Boots.
  • Boot Base plate guide holes for wall widths greater than or equal to 5.5" accommodate ⅞" through-rods for Light, Plus, Small, and Medium Boots. For Large Boots, the base plate guide holes accommodate 1 ¼" through-rods. To transition from a Large Boot with 1 ¼" through rods to any other boot type, a Transition Boot Kit is required, which will accommodate 1 ¼" through-rods on the base of wall, and ⅞" through rods at the head of the wall.

StiffWall consists of two Column/Boot Assemblies (at each end post) and Flat Strap (2 sides of X-bracing). The StiffWall fits into or is embedded into the load bearing and non-load bearing walls. Do your stud take off as normal and order the Column/Boot Assembly and the Flat Strap as separate items. When ordering columns, determine the height of the bearing wall. TSN will size the StiffWall Column/Boot Assembly factoring in the dimensions of the boots at top and bottom. Each column is shipped with the boots pre-attached at the top and bottom as shown in the image below.

TSN_SW_Column_Boot_Pallet

The added value of the pre-installed boots minimizes tolerance issues during erection. Simply specify the clear span of the bearing wall system and TSN will ship the Column/Boot assembly to meet the given wall height at a tolerance of +0/-⅛".

TSN_SW_Column_Boot_Assy

 

Nomenclature

StiffWall/TSN_SW_Column-Boot_Assy_Nomenclature

TSN's Product Catalogs are an essential resource for the design of cold formed steel. Developed by Engineers, the catalogs contain design data for members connectors, and fasteners.

StiffWall® Shear Wall System and the rest of TSN's StiffWall Products can be found in the following Catalogs:

 
 
For a full list of our product catalogs, specification sections, inspection checklists, and research reports please click here.