Standby power system enclosures must withstand loads produced by hurricanes and windstorms. These enclosures must endure wind loads that are determined by many complex factors. The International Building Code is among the standards that have been created to establish common methodology for design and analysis to minimize losses due to wind events. U.S. building standards have also evolved, along with codes for electrical and mechanical systems. The latest edition of building standards is embodied in the International Building Code (IBC 2000, 2003, 2006, and 2009), which sets requirements for structures and ancillary systems, including standby power systems. Building owners and power system specifiers should be familiar with the wind-load compliance provisions of the IBC with respect to power system equipment.
International Building Code (IBC)
In 2000, the International Code Council (ICC) issued its first version of the IBC. While most of the IBC deals with life-safety and fire protection of buildings and structures, it also addresses wind-load design requirements for both buildings and components attached to them. The IBC has been updated every three years, and each edition references standards from a variety of sources, such as the design requirements originally promulgated by the American Society of Civil Engineers (ASCE 7-05) in its Minimum Design Loads for Buildings and Other Structures.
While the IBC has an international label, currently it only refers to building standards in the U.S. All states and many local authorities have adopted a version of the IBC, either the 2000, 2003, 2006, or 2009 edition. Most states have adopted the code at the state level and other local governments have adopted versions of the code at the municipal or county level. The vast majority of states have adopted the 2006 version, while fewer states have adopted the 2003 edition and several are still referencing the 2000 version. Several U.S. territories have adopted the 2009 version, which is now available for adoption by the states.
While the government does not mandate IBC adoption, its adoption has been encouraged-and in some cases required-to ensure funding coverage by the Federal Emergency Management Administration (FEMA). Generally speaking, the requirements for wind-load design are very similar regardless of which version of the code a state has adopted. The following link provides information on the IBC adoption status for each state: http://www.iccsafe.org/gr/Documents/stateadoptions.pdf.
The U.S. wind-speed map provides information on basic wind speed in miles per hour in geographic zones. The first step to identifying wind load requirements for a standby power system is to determine the installation location’s basic wind rating speed. While most of the U.S. has a basic wind rating speed of 90 miles per hour, special regions, particularly along the Atlantic and Gulf coasts, have ratings of up to 150 miles per hour. Figure 1 shows basic wind speed versus geographic regions in the United States.