47.5 MB - The Whole Building Design Guide

Figure 3-78:Collapsed hospital lightfixtures caused by severecorrosion (see inset).Hurricane Ivan (Florida,2004)Communication towers and poles: ANSI/C2 provides guidance fordetermining wind loads on power distribution and transmissionpoles and towers. AASHTO LTS-4-M (amended by LTS-4-12,2001 and 2003, respectively) provides guidance for determiningwind loads on light fixture poles (standards).Both ASCE 7 and ANSI/TIA-222-G contain wind load provisionsfor communication towers (structures). The IBC allows the useof either approach. The ASCE wind load provisions are generallyconsistent with those contained in ANSI/TIA-222-G. ASCE 7,however, contains provisions for dynamically sensitive towers thatare not present in the ANSI/TIA standard. ANSI/TIA classifiestowers according to their use (Class I, Class II, and Class III). Thismanual recommends that towers (including antennae) that aremounted on, located near, or serve critical facilities be designed asClass III structures.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-91