Hold-down Database

Important Note – These are descriptions to changes implemented in WoodWorks Shearwalls for version 9 and may not reflect current behavior.

The program includes a database of standard hold-downs, which you can edit using a database editor incorporated in Shearwalls to update hold-down properties or add new hold-downs

1. Database File

   The Database folder of the WoodWorks installation contains a file called Holddowns.mdb, which is a Microsoft Access database of hold-downs used by the Shearwalls program. Shearwalls now includes an editor to modify the database, but it is also possible to modify the file directly via Microsoft Access.

2. Database Structure

   The database consists of two tables, a Hold-down table that contains the properties of the hold-down that are relevant to Shearwalls design, and a Displacement table which contains hold-down capacities and displacements corresponding to each combination of minimum stud width and depth. The record in the displacement table contains a reference ID to the hold-down that uses that displacement record.

   1. Hold-down Table

      The hold-down table contains the following data:

      • Name
      • Horizontal fastener type ( bolts or nails)
      • Number of horizontal fasteners (per bracket or strap)
      • Horizontal fastener diameter
      • Whether it includes an anchor bolt
      • Anchor bolt diameter
      • Whether published elongation and fastener slippage are combined into one displacement
      • Whether published elongation includes the anchor bolt, or it is for the bracket/strap only
      • The maximum anchor bolt length for which the published elongation applies
      • Whether for this hold-down, we use displacement at maximum capacity for deflection analysis
      • Whether the hold-down includes a shrinkage compensation device
      • Whether the hold-down is to be used as the default hold-down for new projects in Shearwalls

      The meaning of these variables is described more fully in the section on Database Input.

   2. Displacement Table

      The hold-down displacement table is needed for hold-downs for which the entire assembly displacement is published. For those hold-downs for which only the bracket or strap elongation is published, then only one displacement record is needed, corresponding to the elongation of the bracket or strap. The displacement of anchor bolt and horizontal fasteners is calculated separately by Shearwalls using the information in the Hold-down table.

3. Initial Hold-downs

   The file in the Shearwalls installation contains a limited number of hold-downs, from the Simpsons Strong-Tie Bolt Hold-down Evaluation Report 0143 (June 2009, expires June 2010) and the Simpson Strong-Tie Nail Hold-down Evaluation Report 0130 (Dec 2008, expires Dec 2009).

   1. Bolted Hold-downs

      The hold-downs in the initial database that are connected to the upper and lower studs via bolts, from Evaluation Report 0143, are HD2A, HD5, HD7, HD9, HD12, and HD19. For each of these, there is a corresponding hold-down, e.g. HD2A-2, for which the displacements are taken from Table 2 of the evaluation report. For the hold-downs from Table 2, the displacement values are for the hold-down bracket only, and the anchor bolt elongation and horizontal bolt slip are analysed separately by Shearwalls. The displacement values for hold-downs from Table 1, e.g. HD2A, are for the entire hold-down assembly.

   2. Nailed Hold-downs

      The hold-downs in the initial database that are connected to the upper and lower studs via nails, from Rvaluation Report 0130, are LTT19 and LTT4. The displacements for these hold-downs are for the entire assembly (nails, anchor bolt, and strap). However, it is possible to enter nailed hold-downs into the database for which these components are analysed separately by Shearwalls.

   3. Strap Hold-downs

      There are no hold-downs in the initial database consisting of one continuous strap without an anchor bolt; however it is possible to add this type of hold-down to the database.

4. Single vs Double Bracket Hold-downs

   The displacement data in the hold-down database applies to just one bracket or strap of a hold-down. In the program, hold-downs designated as double-bracket have the displacement values doubled, and the maximum anchor bolt length is also doubled. The capacity data applies to each bracket of the hold-down, and is never doubled.

   When creating a hold-down with a continuous strap, you can either

   • enter hold-down data that apply to the elongation of the entire strap and the total number of fasteners, top and bottom, and designate it as single-bracket in Shearwalls
   • enter hold-down data that apply to the elongation of ½ the strap, and the fasteners on one level, and designate it as double-bracket in Shearwalls.