01 / Building Dimensions
02 / Loading & Zone
Section 5, NZS 3604:2011: Bracing demand is expressed as Bracing Units (BU). BSDU = wind-induced demand; BSDD = earthquake-induced demand. The controlling demand is the greater of the two. Total bracing provided must equal or exceed the demand in both directions of the building.
03 / Result
Enter building dimensions to calculate bracing demand
Bracing demand by direction and load type
| Direction | Wind (BSDU) | Earthquake (BSDD) | Governing Demand |
|---|
NZS 3604:2011 — scope and limitations. This calculator provides an indicative bracing demand estimate using the NZS 3604:2011 Section 5 simplified method for rectangular buildings. Buildings in Very High and Extra High wind zones, or in Earthquake Zones 3 and 4, may require specific engineering design regardless of size. Actual bracing design requires: arrangement of bracing lines, compatibility of bracing element capacities with demand, drift limits, and detailing for hold-down forces. Buildings outside NZS 3604 scope (complex shapes, irregular plan, > 3 storeys) require specific engineering design. All results must be verified by a Chartered Professional Engineer.
Bracing Demand — Key NZS 3604 Parameters
| Zone | Zone Factor (Sp) | Wind Region | Notes |
|---|---|---|---|
| Earthquake Zone 1 | 0.65 | — | Low seismic hazard |
| Earthquake Zone 2 | 0.80 | — | Moderate seismic hazard |
| Earthquake Zone 3 | 1.00 | — | High seismic hazard |
| Earthquake Zone 4 | 1.20 | — | Very high seismic hazard |
| Wind Low | — | Region A | Basic wind speed ≤ 32 m/s |
| Wind Medium | — | Region A/B | Basic wind speed 32–37 m/s |
| Wind High | — | Region B/C | Basic wind speed 37–44 m/s |
| Wind Very High | — | Region C/D | Basic wind speed 44–50 m/s |
| Wind Extra High | — | Region D | Basic wind speed > 50 m/s — specific design |