Seismic Detailing Class Lookup
Intensity, system and height in; detailing class and height check out.
Inputs
Result
Formula
| Lookup | Class = Table 6.1.2 (intensity × system × height band) |
| Height bands | Frames at 24 m; frame-wall at 24 / 60 m; walls at 24 / 80 m |
| Class B | Detailing measures taken one degree higher; no upgrade at intensity 9 |
| Height limit | Table 6.1.1, at the original intensity, not upgraded |
| Over-limit | Above the maximum height requires an out-of-code review |
Intensity 7, moment frame, 30 m, class C: above 24 m so the frame is detailing class 2; the 7-degree limit for frames is 50 m, so 30 m is within it.
FAQ
Why one degree higher for class B - intensity or detailing?
Detailing, not seismic action. Class B buildings (hospitals, schools, large retail - those that must stay in service or hold crowds after a quake) are analysed at the local intensity but detailed one degree higher, which drives the detailing class, confinement and minimum reinforcement. No upgrade applies at intensity 9.
Does a lower class number mean stricter detailing?
Yes - class 1 is the strictest, class 4 the loosest. A higher class means the member is expected to deform and dissipate more energy, so ductility demands rise: longer confinement zones, tighter hoop spacing, higher minimum reinforcement and stricter axial load ratios.
What if my building exceeds the maximum height?
It becomes an out-of-code high-rise and needs a special seismic review by a provincial expert panel before construction drawings can be approved. In practice you either change the system (a frame at 50 m becomes a frame-wall at 120 m) or go to performance-based design. Adding reinforcement does not solve it.
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.