Reinforce Existing Steel Roof Diaphragm At New Opening

2 the original structural design assumptions e g.

Reinforce existing steel roof diaphragm at new opening.

1 the design live load is increased at the new stair landing area thereby overloading adjacent portions of the floor. Apply construction adhesive along the edge of the truss to strengthen the connection to the plywood roof deck. Using 5 8 inch puddle welds for attaching deck to supports and 10 sidelap screws we find the nominal shear strength in the table for 0 0295 inch thick wr deck is 0 740 klf using a 36 4 12 inch o c support fastener. A concrete floor is relatively rigid compared to steel moment frames whereas a metal deck roof is relatively flexible compared to concrete or masonry walls.

Wood diaphragms are generally. In buildings with wood diaphragms and reinforced concrete or masonry walls the most common chord members are reinforcing steel placed in the wall at or near the roof diaphragm elevation and a structural steel angle bolted to the wall. The maximum unit shear on the wall diaphragm is also equal to the roof reaction r divided by b. The corresponding diaphragm chord forces are therefore equal to m divided by the diaphragm depth b.

Where the existing chord member is adequate rehabilitation may be limited to enhancing shear transfer. Evaluation of existing structures. The proposed opening may affect existing floor structures in one or all of the following ways. Put on the adhesive as you would caulk.

September 2015 the fourth edition of the sdi diaphragm design manual ddm04 replaces the third edition ddm03. Using the steel deck institute sdi diaphragm design manual third edition we can determine the required deck fastening. Once the opening is located relevant existing floor structures must be carefully assessed. The maximum roof diaphragm moment m equals ww wl x l2 8.

Stiffen trusses by joining them with 2x4s running from one end of the house to the other.