Walls and Slabs

Background

In this worked example, we’ll go through the design process of a shear wall for a two story building. This example references the Aghayere Structural Wood Design: ASD/LRFD Example 7.3. Note that the floor-to-floor height has been changed to 12ft in the example. If you’d prefer to follow along with the video tutorial, click here

Given Information

• The floor-to-floor height is 12 ft
• 4 openings with two on each story, as shown in the below image
• An unfactored lateral wind load of 20 psf is assumed. This value is normalized for service level (i.e. 20 psf = 0.6W)
• ultimate wind shear load: 12,000 lb on the first floor, 13,200 lb on the second floor

Entering your Design Criteria

The full wall length is 60 feet with a story height of 12 ft for each of the two stories. We know there’s an opening at 12 ft and an opening at 36 ft. The opening width is 12 ft and the height is centered from 2 to 8 ft.

The applied loads on the roof (upper) floor are determined to be 13,200 lb of shear load over both lateral walls. Half will be applied to the shear wall we are designing and there will be a parallel shear wall on the other side of the structure that supports the remaining half of the load. The second (lower) floor will carry 12,000 lb of shear load, similarly carrying half the load per shear wall.

Remember to include the unfactored wind loads here, so we will need to divide by 0.6. ClearCalcs will automatically factor these values for you, however since the example gave this value as a factored load, we need to divide by the 0.6 factor so we don’t consider it twice. Our ultimate wind shear load on the first floor will be 10,000 lb (=12,000 lb/0.6/2 walls) and the second floor will be 11,000 lb (=13,200 lb/0.6/2walls)

For the second floor, the gravity dead loads we want here are 20 psf by 12 ft (240 psf) and 40 psf by 12 ft (480 psf) for the transient load. Similarly, for the first floor, our dead load will be 20 psf by 12 ft/2 (120 psf) and our transient load will be 40 psf by 12 ft/2 (240 psf).

Here, we can see that our chords are not passing in compression and that’s because we’re using 2x4s right now. To design this, we want to upsize our chords. We potentially want three layers of chords and can increase our number of stud plies, or can change the stud size and grade. We can look at our member selector to see which member produces a passing design, and try a 2x6 AYC SS! If our design did not have enough capacity to support the shear wall force, we could modify the sheathing and nailing to increase that strength.

The final passing design has studs at a 16” spacing with a 3 ply - 2x6 at the end chords. As well, we have a 7/16” OSB sheathing and a nail pattern of 8 diameter nails at 6” spacing.