Roof Diaphragm Openings

A shear wall however is a vertical cantilevered diaphragm.

Roof diaphragm openings.

A roof diaphragm shall be provided by attaching a minimum of 3 8 inch 9 5 mm wood structural panel which complies with section r803 to roof rafters or truss top chords in accordance with table r804 3 buildings with 3 1 or larger plan aspect ratio and with roof rafter slope pitch of 9 12 or larger shall have the roof rafters and ceiling joists blocked in accordance with figure r804 3 7 2. 2306 2 4 gypsum board diaphragm ceilings. For a diaphragm with openings draw a free body diagram through it. For shear look at the force acting on the net area.

A 20 m x 30 m building has a wood diaphragm on cmu walls as shown in figure 1. In its most basic form i e. You ll probably need some kind of chord element around the opening to make sure the diaphragm isn t overstressed in bending. There are a number of openings in the diaphragm through which structures pass between the thorax and abdomen.

Gypsum board diaphragm ceilings shall be in accordance with section 2508 5. The in plane shear transfer demand at the wall shall be calculated. Openings in shear panels that materially effect their strength shall be fully detailed on the plans and shall have their edges adequately reinforced to transfer all shear stresses. 2306 2 3 double diagonally sheathed lumber diaphragms.

The diaphragm itself does not have a bracing unit rating but is used when bracing lines exceed 6m separation. Most openings of any significant size should be checked. A diaphragm is a flat structural unit acting like a deep thin beam. Double diagonally sheathed lumber diaphragms shall be designed and constructed in accordance with af pa sdpws.

It is strongly recommended that analysis for a diaphragm with an opening should be carried out. Diaphragm openings immediately adjacent to the shear walls shall be less than 25 of the wall length for life safety and 15 of the wall length for immediate occupancy. Wood diaphragm on reinforced cmu shearwalls neylon et al 2013. A diaphragm structure results when a series of such vertical and horizontal diaphragms are properly tied together to form a structural unit.

Diaphragm design with openings. There are three large openings the aortic the esophageal and the caval opening plus a series of smaller ones. A gib plasterboard ceiling diaphragm is a stiff and strong horizontal element which will effectively transfer loads to connected bracing walls lines exceeding 6m or 7 5m with dragon ties to a maximum of 12m. The term diaphragm is usually applied to roofs and floors.

Using this basic concept the diaphragm shear forces can be determined and generally the same principles applied even with the introduction of roof openings or irregular building geometry. Roof chord continuity 4 5 1 4 openings at shear walls. A rectangular uninterrupted plane a diaphragm behaves primarily as if it were a short deep beam figure 1.