Structural Design Basics
Sizing
A glulam beam (GLB) can have 2-3 times the load capacity of a similar sized solid timber beam in bending capacity and nearly one and a half times the shear value.
For example, a beam that is 10′ long and has a continuous force of 40 pounds per square foot live load and 10 pounds per square foot of dead load with a tributary of 6 feet will have the following values:
4X10 HF/#2 will have a bending ratio of 91% of what is allowable and 40% of its potential shear value.
3-1/8X9 24F-V4 DF/DF glulam beam will have a bending ratio of 45% of what is allowable and 29% of its potential shear value.
For this reason, it is common to see engineered products in use were large forces are at play, or where a smaller beam size is preferable. If the tributary is increase to 16′, this becomes more evident.
8X14 Hem Fir #2 will have a bending ratio of 82% of what is allowable and 34% of its potential shear value.
5-1/8X9 24F-V4 DF/DF glulam beam will have a bending ratio of 73% of what is allowable and 47% of its potential shear value.
While the GLB has a lower shear ratio than the solid timber beam, it remains at under 50% of its critical point with the loads listed applied and is substantially smaller than its counterpart.
Don’t concern yourself with the initials HF/#2 and 24F-V4 DF/DF, these are notations for specie of wood, clarity and member properties. I used standards here for the western U.S. You can find more information on glulam beams on the APA Website.
CONNECTORS
Simpson MASA and MASAP Mudsill Anchors have been banned from use in some areas, especially when seismic forces are in play. These hangers tend to be installed incorrectly, and therefore are not only loose against the wood sill, but also tend to be exposed to the elements and subject to corrosion. While they are galvanized, deep scratches during installation can pierce the coating and start the corrosion process from the day of installation.
Think of this like having the top laces of your boot tied loosely. Nothing feels awkward until you stand up and with a little movement, even the bottom starts to loosen.