Engineering - For beginners, Part 4

[RAB]

Engineering - For beginners, Part 4

Comparing Code/Design books to deflection rules mentioned in parts 1-3

Code Book vs. engineered examples-
2x4 supporting roof only, 16" OC, with sheeting, default wind load.

93.5"
Code book says ok to use –
Engineered deflection ratio – 1/480

2x4 9'
Code book says ok
Engineered deflection ratio – 1/300

2x4 10'
Code book says ok
Engineered deflection ratio – 1/230

2x4 11'
Code book says ok
Engineered deflection ratio – 1/175

2x4 12'
Code book says ok but do not exceed this length
Engineered deflection ratio – 1/135

2x4 16'  8"OC
Code Book says ok
Engineered deflection ratio – 1/150

Most Code/Design books use a reduction factors for walls of 2 or more studs so a slightly longer stud can be used.
Notice how the 11' stud just exceeds the 1/180 ratio.
16' stud has a similar ratio but the OC distance is 8".

From Part 3
Recommended deflection ratios for Exterior walls with non-brittle finish = 1/360
There is a slight conflict between code ratios but the reduction (or how much bigger can I make this factor) makes up this difference.

Interested readers – this is a multipart series
Engineers please excuse the simplification that this forum dictates.

Ryan B