Square Angle vs. Triangular

Following are some points to consider when specifying towers. As you will see, the square angle design has no advantage whatsoever over the triangular design, and the triangular design has many advantages over the square design. This is evidenced by the fact that the majority of the world's major tower/mast manufacturers operate in an environment where the finest quality raw materials are available, and are not limited to a certain steel supply. These modern manufacturers provide triangular towers as their primary product.

1. Square tower design is old fashioned and antiquated. Some designs date back to the 1800s and were based on availability of material, existing design capabilities and ease of manufacture. Almost any steel fabricator can design and manufacture square angle towers or masts. Square angle towers are specified in many cases because of the long standing designs that have not been updated over the years. These structures have been the accepted standard, since many departments and users do not have the in-house structural engineering capacity to evaluate modern designs, and take the time to update their requirements.

2. Square tower design is very popular in developing countries where updated technology and sophisticated machinery are not available yet. It exists only because there is no other choice, and what was good enough 100 years ago, is all that is available today.

3. Towers and masts constructed from angle material have a much higher wind load than the more sophisticated triangular round member tower. A triangular round member tower is much more aerodynamic and therefore has lower wind resistance.

4. Because of the higher wind load on the structural members, more reinforcing pieces are necessary, and therefore the structure when completed has many more components and connections than a triangular tower.

5. A square tower with all of this extra material, is no stronger than a triangular tower designed for a similar load. There are international standards developed for tower design such as ANSI/TIA/EIA-222-F-1996 that govern proper tower/mast design for the communications industry.

6. As a result of the square angle design, there is more labor involved to assemble the material, more possibilities of pieces not fitting, more connections to become loose and require maintenance.

7. Triangular towers however are lighter in weight thus saving freight costs, and are constructed of fewer pieces. This is possible because of the higher strength steels that are currently available for the more high-tech tower/mast designs.

8. Triangular towers only require 3 foundations, square towers require 4. There are considerable cost savings in civil works and concrete using a triangular design.

9. From the standpoint of deflection and twist, the triangular pipe tower is stronger and more rigid pound for pound.

10. With round main members (legs) equipment such as dish mounts, platforms etc. are mounted with 'U' bolts, and therefore can be moved from location to location without drilling additional holes in the structural members of the tower. Antenna mounts for example can be added to the structure without any field punching, drilling or welding.

11. There is an old fashioned argument that pipe members corrode from the inside, and since the corrosion is hidden, it cannot be maintained or corrected. Back when pipe members were first used in construction, the material was not hot dip galvanized inside after fabrication. With today's modern fabrication procedures and galvanizing technologies, this condition does not exist. Back to back angle members can also corrode from the inside, and cannot be maintained. The secret is in the fabrication/galvanizing procedure. See more in FAQ.

12. Due to the availability of larger sizes of higher strength round structural steel shapes, round member pipe/solid towers can be designed with single piece main structural members. Angle towers require 'back to back' bolted or welded members ("built up" sections) to provide the strength required for some of today's tremendous antenna loads and tower heights.

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