7.1 Diaphragms
There is significant tensile capacity at reentrant corners or other locations of plan irregularities.
For buildings designed and constructed in accordance with the 1989 or later editions of Part 2, Title 24, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the strength of the diaphragm in the vicinity of corners. Evaluate the chord/collector requirements at the reentrant corners and other locations of plan irregularities by applying the maximum of the diaphragm force and the calculated story force to a model of the isolated diaphragm. All elements that can contribute to the tensile capacity at the reentrant corner may be included with appropriate consideration given to gravity load stresses. Conforming buildings which fail this check shall be placed in SPC 4.
There are continuous cross ties between diaphragm chords.
For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the adequacy of the path for wall anchorage forces into the diaphragm. A cross tie is a beam or girder that spans the width of the diaphragm, accumulates the wall loads and transfers them, over the full depth of the diaphragms, into the next bay and on to the nearest shear wall or frame. Calculate the wall anchorage forces according to Section 2.4.5, and check that these forces can be developed, element by element, in the diaphragm.
There is reinforcing around all diaphragm openings larger than 50 percent of the building width in either major plan dimension.
For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the strength of the diaphragm in the vicinity of the openings. Check the adequacy of the diaphragm to transfer stresses around the opening.
Diaphragm openings immediately adjacent to the shear walls constitute less than 25 percent of the wall length, and the available length appears sufficient.
For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the length of diaphragm needed to transfer shear to the wall or frame and to provide lateral support for the wall or frame.
Procedure for diaphragm shear: Verify that there is a path of forces and sufficient strength to deliver the diaphragm shear to the shear wall. The diaphragm shear is the demand.
Procedure for lateral support of the wall: Treat the wall as a portion of the building using Fp as the demand.
Diaphragm openings immediately adjacent to the braced frames extend less than 25 percent of the length of the bracing.
For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is similar to that described above for openings at shear walls.
Procedure for diaphragm shear: Verify that there is a path of forces and sufficient strength to deliver the diaphragm shear to the braced frame. The diaphragm shear is the seismic demand.
Procedure for lateral support of the frame: Treat the frame as a portion of the building using Fp as the demand.
Diaphragm openings immediately adjacent to exterior masonry walls are no more than 8 feet long.
For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is similar to that described above for openings at shear walls.
Procedure for diaphragm shear: Verify that there is a path of forces and sufficient strength to deliver the diaphragm shear to the shear wall. The diaphragm shear is the demand.
Procedure for lateral support of the wall: Treat the wall as a portion of the building using Fp as the demand.