Why there is no option to include accidental load for seismic design in canadian code NRC 2005?
there is this option in IBC. canadian code calls for minimum torsion eccentricity = 0.05 or 0.1 dns ( dimension perpendicular to seismic force direction)
It is true that there is no option to include accidental torsion as per the NRC 2005 code from within the seismic definitions. However with the implementation of floor diaphragm feature, one can now define rigid diaphragms and then when one applies the seismic load to the structure, one can add the DEC and the ACC parameters to the input which takes care of both the inherent torsion or natural torsion ( due to eccentricity between Center of Mass and Center of Rigidity ) and the Accidental torsion. Here is a sample input
…
LOAD 1 LOADTYPE None TITLE LOAD CASE 1
NRC LOAD X 1 DEC 1 ACC 0.05
You may refer to technical reference manual section 5.32.12.2.1 for more details on these inputs.
An example model is also attached for your reference.
Rigid_dia_equivalent _static.STD