Structural Analysis

One of our most common engineering requirements is to determine if an existing tower is over-stressed or if an existing tower can safely accommodate additional loading. If you are interested in more information or would like a quote request for a structural analysis, please submit your email address in the quote request form and we will contact you shortly. 

The following are common questions regarding tower structural analysis:

Just what is a “structural analysis”? A visual inspection of a tower shows only the physical condition of a tower such as rusting, cracked welds, bent members, etc. While a visual inspection is extremely important, it will not show whether a tower is overstressed by the loads it is supporting. A structural analysis uses mathematical engineering formulas for stress, along with the known behavior of different materials under load to determine if anyone point on the tower is stressed beyond safe limits. By using state-of-the-art computer software, we can create a mathematical model of any steel structure and quickly determine the stresses at hundreds of points on the tower.

Who determines what is a “safe load”? The Telecommunications Industries Association (TIA) has developed a written standard which provides minimum criteria for specifying and designing steel antenna towers and antenna support structures. The current standard represents years of engineering studies and has been accepted as an industry standard.

What information is required? An analysis requires all of the tower dimensions, location, and type of antennas, and local climate conditions. Information can be obtained from a combination of original tower drawings and tower records. 

What if the information is not available? Dimensions can be obtained from an on-site mapping of the tower. Ehresmann Engineering can do that for you at your request. Some assumptions may need to be made. For example, steel is generally considered to have a minimum yield strength of 36 kilo-pounds per square inch (ksi) unless original manufacturer specifications are known to confirm actual parameters. Unless informed otherwise, we must also assume the tower steel does not have hidden defects such as hairline cracks, internal corrosion on tube members, or excessive corrosion on anchor underground.

How do we determine climate data? The TIA standard referenced above has established a typical ice thickness and wind speed for every county in the United States. Due to the low probability that an extreme ice load will occur simultaneously with an extreme wind load, the wind load for tower design purposes is normally reduced when considered to occur simultaneously with ice. If more extreme conditions than those outlined by TIA are known to occur at a specific site and/or the owner/customer would like more conditions considered, those conditions must be specified by the owner/customer.

What is the cost of an analysis? The price varies with the size, type, and complexity of the tower. Ehresmann Engineering will quote you a firm price in advance on any structure. A re-analysis of the same tower is provided at a reduced cost to consider various options in antenna loading, environmental conditions or to consider tower modifications.