Answer Happy

LONGITUDINAL FORCE=WL. 23.33 23.3323.33 TRANSVERSE FORCE= =WT -2X4 SUB PURLINS PURLINS HEADER 15 GRDER 70 4@30=120 ROOF FRAMING PLAN Roof sheathing is 3/8 inch, Structural I plywood, span rating 24/0. The red circled area shows the plywood panel layout. The long side of panels is oriented perpendicular to the girders (framing). Assuming that the sheathing has already been designed to safely carry D and L loads, check the roof to resist only the following two seismic load cases: Wt = 650 plf W₁ = 1200 plf Use LRFD methods.
Design steps. All references are in the SDPWS. 1. Determine the "cases" that matches the sheathing panel layout. Recall there are cases 1 through 6, see the bottom of Tables 4.2A-D. One case will be for the wt load, and one case will be for the wL load. 2. Check the aspect ratio of the roof plan layout, see Table 4.2.4. 3. Factor the loads using the appropriate LRFD combination from ASCE 7. 4. Calculate the shear reactions Vt and VL (in lbs), then the unit shears vt and vL (in lb/ft). 5. Provide the nominal unit shear capacities from Tables 4.2A-D. Hint: check the capacities for both blocked and unblocked diaphragms. 6. Calculate the ultimate unit shear capacities (multiplied by the appropriate LRFD resistance factor). 7. If necessary, determine where blocking is required in the transverse and longitudinal directions. a. Specify the blocking area on a roof plan sketch. b. b. Specify the blocking size and width of nailed face. c. c. Specify the nailing size and penetration depth. d. d. Specify the nailing spacing at applicable regions. These are your options: i. diaphragm boundaries ii. continuous edges parallel to loads iii. all panel edges iv. other panel edges