The API 4F specifications for wind loads based on the velocity component approach is integrated into the PSE Petroleum Structural Engineering software. Accordingly, drilling structures are classified based on their Structural Safety Level (SSL) and their offshore or onshore location.
The design reference wind velocity value represents a 3-second gust wind measured in knots at an elevation of 10 m (33 ft) in open water, with an associated return period of 100 years.
The API 4F specifications are applicable to the following wind environments:
– Operational wind
– Erection wind
– Transportation wind
– Unexpected wind
– Expected wind
The PSE software allows different configurations of the drilling structure models according to a given wind environment. The program requires the input of the rated design wind velocity, Vdes, and accounts for the design reference wind velocity and wind velocity multiplier. The program computes the local wind velocity, Vz, by scaling the rated design wind velocity by the appropriate elevation factor, ß, in order to obtain the velocity for estimating the wind forces.
A wind profile in a selected direction provides the wind intensity that generates the wind loads to structural members and surface areas. As many as required wind directions can be defined through different basic loads.
Member selection procedures allow the application of the wind profile to the entire structure or to specific zones and excluding members behind or in front of wind walls. It is possible to apply the API 4F wind loads directly to elements such as equipment, wind walls and other objects attached to the drilling structures.
The shape factor is automated in the PSE software for various section shapes. The program accounts for the gust factor and the reduction factor for shielding by members and appurtenances.