Wind load combinations for structural design of tall buildings

For a building design, there are usually three wind load components to consider: two orthogonal horizontal loads; and one torsional load. As each load component generally does not reach its maximum value at the same instant as the other components, nor even for the same wind direction, it is important to consider how these predicted peak load components should be combined for structural design. Based on the consideration of the cross-correlations of the various load components and the practical range of structural influence factors, an approach to determining an optimized set of linear load combination factors is given. The proposed set of load combinations possesses the property that, for any given structural member, there will be at least one of the combinations which causes the 50-year load effect (e.g., stress) to be reached or slightly exceeded. With this set of load combinations, the predicted wind loads from wind tunnel tests and the follow-up analysis can be presented in the form of equivalent static wind loads for a particular return period, typically 50 years, somewhat similar to the format of a building code. An example of use of the proposed load combination approach is given.