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Connection Types in Wood-Frame Buildings (3)

Views: 227     Author: Site Editor     Publish Time: 2018-11-14      Origin: Site

Connection Types in Wood-Frame Buildings (3)

Problems Need to Pay Attention

Notching problem

While notching technique is essential to traditional joinery and may be required in this field due to many reasons, but if notches and holes aren’t made properly, or not made according to approved drawings, the capacity of the connected members will be significantly reduced. Good news is, there is guidance on notching, and the related industry workers have established many recommendations on applicable notches sizes for different materials. When using a notch, designers are supposed to take lag screw or 6-8’’ self-tapping screw into account. When developing a crack, the screw will keep it from going down the length of the beam.

Moisture Effects

When the equilibrium moisture content changes the wood members will expend or contract to some degree. Normally, the expansion in the direction parallel to grain is not obvious, while in direction perpendicular to grain can be considerable, which must be considered in the connection design and applications. The common rules show that, the wood members often experience a one percent radial or tangential change when the moisture content changes four percent. So, it will be very important to consider the connection design and details when using wood members, so that the shrinkage will not be restrained. Or it will result in excessive tension stresses and splitting phenomenon. 

There are several specific shrinkage issues as follows you are supposed to know.

1.Beam to column connections: Continuous full-depth side plates will restrain the wood shrinkage, which may cause some problems, like splitting. Solution: use smaller discontinuous side plates to transmit forces and allow members to move in acceptable level.

2.Beam to beam connections: The fasteners located near the top of the supported beam will restrain the shrinkage of wood members, resulting in splitting. Solution: Place the fasteners at the bottom of the supported beam. The shrinkage can be reduced to the least.

3.Beam to wall connections: When the bolts are located high or low on the beam, the perpendicular to grain stress tension may lead to splitting. Solution: Place the bolts near the bottom of the beam, better with slotted holes, remove the restrain to wood shrinkage.

4.Other issues. Exposed end grain can cause checking and decay. Solution: Redirect the water flow near the wood connection; choose preservative-treated or decay-resistant wood products; use end caps and flashing.

With the development of science and technology, we are sure to find more solutions to current issues in the future.