DaVinci Engineering holds a broad spectrum of licenses and certificates providing 100% engineering services across North America and Internationally for Landa and clients. DaVinci engineering staff are accredited and an active member of CSA, TIA, ASCE (Dynamics of mobile and permanent latticed structures), CSA Technical Committee on Communication Towers and Wind Energy. Engineering is recommended for every tower install to ensure safe antenna and mobile tower deployment. DaVinci Engineers utilize their combined years of experience with custom engineering software and Landa extensive R&D enabling a match for each and every loading configuration requirement. For each tower deployment, the location of the COW, location of guy cables, quantity of guy cables, coaxial cables, specific antenna loading, and antenna elevation are all very critical factors in determining the specifics of that tower. Therefore, we analyze each specific COW deployment based on the above criteria to determine it‘s the feasibility. The TIA-222-G uses the following factors that are considered in the design wind pressure of these towers, we will also be compliant with the new 2016 ANSI/TIA-322 guidelines as they come into operations.
Over the past three decades, the COW manufacturer has documented site-specific data that shows the tower sections failing before any damage to the trailer frame or outriggers.
For example, tower sections have failed due to hurricane winds while the trailer and outrigger showed no signs of damage. This means we verify that the trailer will not tip over based on the assumption that there is not a structural failure within the trailer frame or outriggers.
Per section 1609.1.1 of the 2012 & 2015 International Building Code, communication structures are designed in accordance with the Electronic Industries Association / Telecommunications Industries Association Standards ANSI/TIA-222-G-2, “Structural Standards for Steel Antenna Towers and Antenna Supporting Structures”. This is a nationally recognized standard and is modeled after the American National Standards Institute document known as ASCE-7. The ANSI/TIA-222-G-2 standard was developed by professional engineers experienced in the design of communication structures. A structural failure per LRFD is determined when a structure exceeds its limit-state. This does not necessarily mean that the structure “falls down”. Limit state design requires the structure to satisfy two principal criteria: the ultimate limit state (ULS) and the serviceability limit state (SLS). A limit state is a set of performance criteria (e.g. vibration levels, deflection, strength, stability, buckling, twisting, collapse) that must be met when the structure is subject to loads. In the unlikely event that this COW would possibly fail due to extreme wind load that exceeds the design wind criteria, it would first begin to yield within the tower sections. These COW tower sections have been designed by a qualified professional engineer for a design wind speed that meets the local and regional requirements as well as the ANSI/TIA-222-G. The tower has been properly analyzed with all of the applicable load factors, load combinations, and resistance factors as required by code.
- Structure Class: Used to determine the important factor for the structure based on the hazard to human life, property damage, and the necessity of essential services.
- Exposure Category: An exposure category that adequately reflects the characteristics of ground surface irregularities at the site shall be determined. The account shall be taken of variations in ground surface roughness from natural topography, vegetation as well as from man-made / constructed features.
- Topographic Category: A factor to consider wind speed-up at isolated hills, ridges, and escarpments constituting abrupt changes in the general topography.
- Wind Speed: The basic wind speed and ice thickness shall be at a minimum per the IBC wind maps and shall be considered to come from any horizontal direction.
- Gust Effect Factors: Factors that account for the effects of wind gusting and the calculated response of a tower type structure.
- Load Combinations: Used to determine the “timing” or combinations of loads on the structure at the same time per the 2012 IBC.
With this being said, there are no easy copy/paste answers. If you have a specific set of criteria we can analyze that as a baseline to help create an understanding of the COW’s feasibility. Providing clients detailed pertinent design information with exhaustive wind load reports and specific guying requirements for each install while maintaining Landa proprietary design drawings and calculations. DaVinci is instrumental is the success and survival of your deployment whether on a permanent or temp deployment.
Short answer does not fly an airplane without doing a weight and balance. Same on tower erection of any type, have engineer calculate the build taking into consideration, frequency, antenna size, path stability, full loading, wind, ice, guys, etc. don’t make uneducated guesses and get someone hurt, not to mention the loss of equipment.