Continuous Ties on Gable Roof Diaphragm

[mell9401]

I'm working on a design for a 24'x28' CMU masonry building with a gable roof consisting of wood trusses at 24" o.c. The diaphragm is to be plywood sheathing on the wood roof trusses. The truss to wall connection will be similar to the attached file. The building is in Seismic Design Catagory C. ASCE-07 12.11.2.2.1 requires that "diaphrams be provided with continuous ties or struts between diaphragms chords" to distribute the wall anchorage forces into the diaphragms.

I can see that when loaded in the transverse direction, the trusses will act as the required continuous ties but what is the best way to provide the continuous ties accross the diaphragm between the end walls for the case when the building is loaded in the longitudinal direction? I'm thinking that you could provide blocking between the top chords of the trusses but would you then have to provide diagonal framing from the blocking to the bottom chord of each gable end wall truss to transfer the load from the walls into the continuous ties and then into the diaphragm sheathing?

 

[DaveAtkins]

I would use solid blocking in every other or every third truss space. You must leave some truss spaces open for ventilation.

DaveAtkins

 

[msquared48]

I would use solid 2X blocking between all the trusses with (3) 1.5" diameter vent holes thru each block.

Mike McCann
MMC Engineering