Roof Diaphragm Bracing

Because this sheathing material does not provide a diaphragm at the plane of the roof other means of bracing the roof against horizontal loads must usually be employed.

Roof diaphragm bracing.

When designed correctly a roof diaphragm can reduce or eliminate the need for diagonal bracing. For example the roof may be braced with diagonal metal straps applied to the top of the sheathing or with a layer of plywood or osb over the decking. Diaphragm action is an additional capacity of the panel to transfer the lateral loads to the outside edges of the panel to the eave for roof panels and to the ground for wall panels. At roof level bracing often known as a wind girder may be required to carry the horizontal forces at the top of the columns if there is no diaphragm.

Roof planes less than 6m2 e g. Or installed as a structural ceiling diaphragm in accordance with section 13 nzs 3604 ecoply structural racing and eiling diaphragms as specified in section 3 0 of the ecoply specification installation guide are suitable for bracing components in houses and. In structural engineering a diaphragm is a structural element that transmits lateral loads to the vertical resisting elements of a structure such as shear walls or frames diaphragms are typically horizontal but can be sloped such as in a gable roof on a wood structure or concrete ramp in a parking garage. We decide to use steel angle 2l sections as horizontal bracing to withstand the large axial loads.

The distance from the exteriors vertical bracing are large around 300 ft we have a large axial load in the roof steel deck diaphragm the loads exceed the resistance of the connectors of the deck. The diaphragm forces tend to be transferred to the vertical resisting elements. This stiffness provides stability and replaces the need for other bracing elements. When a roof diaphragm has no openings or obstructions the calculations for shear are.

See figure on the right. Sheathed elements such as walls and a roof covere d with panels and tied together provide additional strength to the building. Usually the floor system will be sufficient to act as a diaphragm without the need for additional steel bracing. Challenges of calculating shear.

Bringing it back to basics you need to understand bracing lines the imaginary lines running along and across the full length or width of the plan for a timber framed building. Dormers porches do not require bracing. In a nutshell ceiling diaphragms under light and heavy roofs are required to comply with nzs 3604 2011.