Wind Load Provisions for Existing Water Towers Undergoing Cellular Antenna Modifications: Standards and Recommendations: Fid-Bau Portal

Wind Load Provisions for Existing Water Towers Undergoing Cellular Antenna Modifications: Standards and Recommendations

McCarty, M. A. / Chang, Y. / Grier, R. B.

Throughout the United States, wireless communication service providers (carriers) mount their antennas to existing water towers, in lieu of constructing their own dedicated structures. With the rapid increase in cellular data consumption and the expansion of coverage, carriers are progressively adding new as well as enlarging existing antenna assemblies. Despite this continuing trend, the standards to which these towers are designed (American Water Works Association AWWA D-100 and AWWA D-103) give little direction on how to address the increase in wind load to the tower structures resulting from the addition of this excess equipment. Though the AWWA standards provide explicit guidance for the design and analysis of the water tank, tower legs, and bracing, the added effects of appurtenances and cellular antenna structures is largely unclear. Therefore, structural engineers have resorted to other standards: the Telecommunication Industry Association (TIA 222-G), American Society of Civil Engineering (ASCE 7-10), and American Institute of Steel Construction (AISC 360-10). However, because AWWA standards exist independently of, and are not referenced by, the International Building Code (IBC), there is little interface between current practices and AWWA provisions, leaving little to guide overall analysis/design of tower additions. This has led to the use of loose and irregular code interpretations, leading to inconsistent outcomes, increased costs, and lost man hours. This paper presents a comparison of multiple design procedures used to mount telecommunication antennas to existing water towers and makes recommendations for a cohesive design methodology to guide and improve current practices.