Reinforce Existing Steel Roof Diaphragm At New Opening

Once the opening is located relevant existing floor structures must be carefully assessed.

Reinforce existing steel roof diaphragm at new opening. The maximum unit shear on the wall diaphragm is also equal to the roof reaction r divided by b. The proposed opening may affect existing floor structures in one or all of the following ways. 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. Evaluation of existing structures.

Stiffen trusses by joining them with 2x4s running from one end of the house to the other. 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. Adding new joists or beams considerations existing interferences piping electrical conduits other interferences removing or relocating could be at a greater expense than reinforcement camber may need to reduce camber in new joists joists can be ordered with shallower seat depths and then shimmed in the field.

Put on the adhesive as you would caulk. 2 the original structural design assumptions e g. 1 the design live load is increased at the new stair landing area thereby overloading adjacent portions of the floor. The maximum roof diaphragm moment m equals ww wl x l2 8.

Importance is the in plane rigidity of the diaphragm relative to the walls or frame elements that transmit the lateral forces to the ground figure 4 29. Where the existing chord member is adequate rehabilitation may be limited to enhancing shear transfer. 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.

It includes information for the design of steel deck diaphragms for roof and floor decks and complies with the requirements of the ansi aisi s310 2013 north american standard for the design of profiled steel diaphragm panels.