The design of telecom infrastructure relies on a thorough knowledge of engineering principals, knowledge of the Standard and a good understanding of the project site. When implementing an infrastructure build-out project, the designer should ask a number of questions. Is the structure on a hill or ridge? What is an appropriate wind speed for the design? Should ice be considered? All of these questions have a critical impact on the design of the structure.
It is all too common for manufacturers to utilize designers that are experienced at operating a piece of software, but lack the engineering background to understand how the software functions and the importance of their design decisions. Sitting in a far-off location, mass-producing structure designs, designers often fail to capture the design criteria that will result in a properly designed structure. Did you know that the simple fact that a structure is on a ridge may increase wind loads on the structure by a factor of 3 as wind gets “squeezed” over the hill?
Furthermore, the Telecommunications Industry Association’s Structural Standard for Antenna Supporting Structures and Antennas (TIA-222-G) specifies design wind speeds on a per county basis, often misleading designers. In one county in Colorado, elevations range from 6,000 to 14,000 feet above sea level. The Standard specifies a design wind speed of 90 mph for the whole of this county, regardless of elevation.
Without knowledge of the project site, a designer could select a 90 mph design wind speed for a mountain-top site in this county while an appropriate design wind speed is on the order of 140 mph. This represents a misjudgment of wind pressure by 2.5 times.
The Engineering Specialties Group always investigates a project location thoroughly, such that accurate design parameters are utilized in a design or while verifying a design.
This article was written by Steve Dorau, project manager and telecom infrastructure group leader.
© Copyright 2011 by the Engineering Specialties Group