4Same Diaphragm, Other Direction In this direction, the diaphragm is considered to be ONE diaphragm.The shear wall on Grid B does not contribute.
5Diaphragm Deflections SDPWS 4.2.2Must account deformation from:BendingShearFastenersChord Splice SlipApplied Technology Council“Guidelines for the Design of Horizontal Wood Diaphragms”, 1981
6Drag Struts Getting the Diaphragm Shear into the Shear walls Drag struts are axial force members that “collect” the horizontal diaphragm shears and redistribute them to the shear walls.Drag struts are PARALLEL to the direction of force.Need to draw an AXIAL FORCE DIAGRAM in order to compute the force a drag strut.The member used for the drag strut is often used as a diaphragm chord when the direction of force changes to the other principle direction.
7Unit Shears on Drag Strut Unit shears (on each side) seen by the drag strut equal the total shear force being transferred divided by the length (on each side) attached to the drag strut.
8Drag Strut DiagramsThe AXIAL FORCE DIAGRAM show the axial force as a function of the length of the member.Note that the same member is a chord when the direction of force changes. Must also handle chord forces.
10More Irregular Shapes Amrhein, James E “Reinforced Masonry Engineering Handbook”, 4th edition
11“L” Shaped DiaphragmsSubdivide into diaphragms according to shear wall locations.
12Subdivided Diaphragm, 1Along Grid B, Shears are inversely proportional to the length of the drag strut.Boundary nailing along the strut can be two rows, one for each dia. or one row capable of handling the sum of the diaphragm shears.
13Drag Strut Diagram, 1The peak force equals L1B*(vA1+vA2) or L1A*(vwall-vA1).
14The Other DirectionDrag Strut in this direction also!
15Subdivided Diaphragm, 2Note that there are different diaphragms in each direction.
17Vertical Offsets Applied Technology Council “Guidelines for the Design of Horizontal Wood Diaphragms”, 1981
18Diaphragms of Variable Depth Length parallel to force varies.Unit Shear varies with the depth.
19Chord Extensions Chord Force varies with depth. Extensions must be designed to anchor the chord into the diaphragm.Length of chord extension affects shear force in diaphragm.Diaphragm shear due to extension = Chord force/length of extension.
20Other DirectionConsider each leg as a cantilever beam in order to determine the moment and resulting chord force.Anchor the chord into the diaphragm as previously described.
21Irregular Examples Applied Technology Council “Guidelines for the Design of Horizontal Wood Diaphragms”, 1981
22Openings In Diaphragms Applied Technology Council“Guidelines for the Design of Horizontal Wood Diaphragms”, 1981