When the applied force at the top of the wall reaches a certain amount, the overturning moment will equal the resisting moment. Even the slightest additional applied force will cause the wall to turn over. Since we cannot allow walls to overturn, we must install anchors to hold them down to the structural elements below. The word "hold-down" (hyphenated or as one word) highlights the purpose. In some cases even where the overturning moment does not equal the resisting moment, hold-downs are required. More on that later.
Hold-downs can take many forms. Some look like straps that emerge from the foundation and nail to the edge or face of a stud. Others connect foundation bolts or threaded rods to the studs via bolts or nails. The hold-down creates a path for forces to travel out of a shear wall and into other portions of the building.
Let's look at our options...
|Simpson Hold-down - New Version|
|This is the basic hold-down used to tie end posts
of shear walls down
to the foundation. This type of hold-down is fabricated from a single
stamped gage plate then bent into the desired shape. Because there
is no welding involved, it is less expensive.
|Simpson Hold-down - Old Version|
|When high hold-down forces are encountered you will
be looking for stronger
connections between the hold-down and post (through bolts) and between the
hold-down and the foundation (anchor bolt). This type of hold-down is made from
a bent plate with a welded bearing washer.
|Simpson Hold-down - New Type|
|Creating a connection between the foundation and the
shear wall need
not involve bolts. This connector relies on an embedded strap similar
to the wall anchors you'd see used in concrete tilt-up construction. Nails
create the connection between strap and stud. This is an FTM hold-down.
|Simpson HPAHD Installed|
|This particular hold-down has been in the catalog
for a number
of years. If there is a drawback to it, it is the presence of the
strap on the nailing surface of the stud. Keep this in mind as
we move on to talk about nailing.
|Simpson HPAHD at Corner|
|The same basic comments stated above apply. The
a strap this close to the end of a wall may cause the wall sheathing
to fit poorly at the corner. The strap may also deteriorate due to its
reduced cover by concrete.