Simpson Strongwalls
For many years garage door openings could be braced with shear walls that were only 18″ wide. The Northridge Earthquake revealed that these shear walls acted like posts and tipped over. The building code therefore changed in the 1997 Uniform Building Code such that walls on either side of a garage had to be a minimum of 4′ wide rather than the 18″ previously allowed.
Sometimes builders did not want this 4′ wide wall on either side of the garage door opening because it meant he had to build an even bigger garage with its added expensive.
Let’s say a retrofit contractor wants to retrofit a garage door opening that has 18″ wide walls on each side. He can’t build a standard shear wall because the building code tells him it must be 4′ wide. Contractors needed a solution so Simpson StrongTie developed Strongwalls that could be very narrow and still perform like a 4 foot wide shear wall.
This table is from the manufacturer’s catalog.
The first column in this table under “Model No.” tells us the width and height of the strong wall. For example, SSW24x7 means the strong wall is 24″ wide and 7 feet tall. The numbers boxed in with red tells us how much earthquake force they can resist. For example, the SSW24x7 can resist 5,405 lbs of earthquake force. A SSW12x7 can resist 955lbs.
DOUBLE SIMPSON STRONGWALL
One of the best things about the strong walls is that you can put two of them next to each other back to back. This is called a “Double Simpson StrongWall”. If we install two SSW24x7s back to back we will be able to resist 10,990lbs of earthquake force and two men can lift them and put them in place. This greatly reduces the labor expense. Notice how the Double Shear Wall resistance of 10,990lbs can resist almost as much as the strongest moment column. It should be obvious why these are usually the best choice.
Here is a YouTube video that looks at a Simpson strong Wall.
