Hold-down Database

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

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.

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.

Hold-down Table

The hold-down table contains the following data:

• Name
• Whether it includes an anchor bolt
• Anchor bolt diameter
• 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.

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.

Initial Hold-downs

The file in the Shearwalls installation contains a limited number of hold-downs, from the Simpsons Strong-Tie ICC acceptance criteria AC155.

Screw mounted Hold-downs

The hold-downs in the initial database that are connected to the upper and lower studs via screws, from the ICC acceptance criteria AC155, are HDU2-SDS2.5, HDU4-SDS2.5, HDU5-SDS2.5, HDU8-SDS2.5, HDU11-SDS2.5, and HDU14-SDS2.5..

Nailed and Bolted Hold-downs

There are no hold-downs in the initial database that are fastened with nails or bolts to the wall studs, however it is possible to add this type of hold-down to the database.

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.

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 designate it as double-bracket in Shearwalls.