Slide 13 of 23
Notes:
For performance-based engineered buildings an ultimate strength design level should be defined explicitly for a maximum wind event of between 475 - 1000 years return period, but considering the additional effects of structural frequency shift and increased damping. At this design level the load factor utilized would be 1.0
Hurricane events are not accurately represented by climatological data, and their return periods can be overestimated by historical analysis.
Dynamic properties of damping and possibly frequency shift can vary with increased wind speed. Virtually all high-rise structures will respond dynamically to wind loads. The associated vibration creates additional internal inertial loads that are additive to the external wind load, resulting in an even greater required load factor for increased speeds
