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PROFESSIONAL SERVICES
Davidson Engineering (DE) is a full service structural and civil engineering consulting company specializing in the design and analysis of existing communication structures. Since 1981 DE has designed, reviewed, and evaluated thousands of guyed, self-supporting, steel and wood monopole structures used for multimedia communications, weather monitoring, power generation, and radar facilities including: NTSC and HDTV television broadcast, FM and AM broadcast, MW, cellular/PCS, paging, 2-way, doppler radar, guyed exhaust stacks, and more. These structures range in heights to 2000 feet tall and span the globe from Argentina to Alaska and from Guam to Cyprus.
Complete, rigorous structural analyses and feasibility studies are performed to establish the standards and code-based load carrying capacity of the structure. DE has designed and analyzed a wide variety of fabricated product of every major tower and pole manufacturer in the US (including Dresser-IDECO, Sioux Falls, and other tower manufacturers no longer in business). Many of these structures stand in the most severe climates on earth. They have been designed to withstand winds in excess of 155 MPH (250 KM/H); have been designed to withstand basic wind speeds of 140 MPH concurrent with radial ice loads up to 4 inches; and have been designed to withstand seismic loads in excess of Richter 8.0 magnitude.
Yet, DE is careful not to apply loads to the structure that are not likely to occur during the structure's useful lifespan. DE investigates local site topography and tower elevation, wind exposure category, structure importance category, local building authority regulations, and climatologic records where available; and works with the Client to ensure that the environmental load application is appropriate for the structure.
Strengthening and modification of existing structures to accommodate tower height increases and the addition of HDTV, cellular/PCS, and other service carriers is a mainstay of DE. Dynamic structural analysis of cantilevered steel monopoles and self-supporting towers is offered as a design specialty. This design specialty is particularly important for certain structures where collocation of added PCS/cellular/wireless carriers is sought in relation to existing steel monopole analysis. Structure fundamental period of vibration and the structure's associated gust effect are calculated (as opposed to merely being assumed a constant value of 1.69 for pole structures as in TIA/EIA 222-F). Dynamic analysis of tall, slender, self-supporting trussed towers and monopoles has become increasingly important where aesthetics and local politics mandate the construction of visibly unobtrusive structures. Earthquake loads often control the design of the top-most portion of the structure; especially in high-risk seismic regions such as California and Nevada, in the San Francisco and Los Angeles vicinities in particular, and in other locations of high seismic activity.
Non-linear Push-Over analysis is offered to evaluate structural performance under extreme load conditions and to predict/control the most probable mode of failure. This is especially important where the tower has the potential of falling outside the communication site property boundary. Professional opinion letters are offered in relation to maximum fall radius in the event of a guyed tower collapse. Measures to minimize guyed tower fall radius and to mitigate risk to adjacent property and structures are described in a comprehensive analysis of the potential collapse mechanisms.
Site visits and tower inspections for existing structures are handled in the most economical manner possible in order to minimize the cost of structural data acquisition. Where information is not available with respect to existing foundation construction, investigation of existing subsurface concrete foundation sizes and determination of reinforcing steel ratio is performed through the use of sub-consultants specializing in Non-Destructive Testing (NDT) of buried concrete 'deadman' and pile foundation systems.
CONSULTATION SERVICE FEES
The services described above (and others) are offered at competitive costs. Over the last few years, DE has invested many thousands of dollars in structural analysis software and computer hardware. This investment has dramatically cut the time required to complete a rigorous structural analysis. As the speed and processing power of low-cost computers have increased, so has there been a commensurate increase in the speed with which a structural analysis can be performed. Contact DE for a competitive structural engineering cost proposal.
In many cases, a cursory review of the structure and the proposed loading will suffice. Numerous structures have been over-loaded by the site manager or tower owner (in order to increase monthly revenues), and these towers are sometimes easily identified as such by a cursory structural review. Many potential clients have been advised to save the money they would spend performing a complete analysis, and apply that money to analysis or construction of an alternate structure.
Also, in many cases, a simple change-out of equipment is proposed by a cellular carrier, for example. Often times the newly proposed equipment loading is identical or nearly identical to that of the currently supported equipment. In such a case, a simple letter recommending the equipment change-out will suffice.
By the same token, a few more dollars spent on engineering may save several thousands of dollars in contract labor and materials. It takes a significant amount of experience to know when the additional expense is justified. However, the client always has the final word when it comes to cash expenditures. DE's goal is to provide competent engineering services at the lowest possible cost to the client.
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