1
American Tower Corporation Twist and Sway – Frequently Asked Questions
Twist and Sway FAQ
1. What is twist and sway and what are the values reprenting?
Twist is the number of degrees that a tower rotates within a plane parallel to the ground. This
时刻英语is illustrated in the diagram below, which shows twist as the angle in which a tower rotates
美丽的小兴安岭教学反思
around its center. Similarly, sway is the number of degrees that a tower rotates within a plane
perpendicular to the ground. This is illustrated in the diagram below and shows a line tangent
冰箱温度如何调节
雨季to the curvature of the tower at the node where the dish is attached to the tower.
2. Where can the twist and sway data be found within an
American Tower Structural Analysis Report?
On reports dated after August 1, 2012 the twist and sway data can be found within a chart (shown below) on the third page of the report in the ction labeled “Deflection, Twist and Sway.” On some towers that have many loads within the loading tables, this information is pushed to the fourth
page. However, the information is still in the ction labeled “Deflection, Twist and Sway.”
Deflection, Twist and Sway*预产期计算公式
*Deflection, Twist and Sway was evaluated considering a design wind speed of 50 mph (Fastest Mile) per ANSI/TIA/EIA-222-F.
Reports dated prior to August 1, 2012 would either have this information shown on the cond page of the report within the ction labeled “Results” or in some cas, this information was not shown wi
thin the report. In cas, plea e the answer to the third question on how to find the twist and sway results from the calculations of an American Tower Structural Analysis Report.
3. Where can the twist and sway data for lf-support and guyed towers be found
within the calculations of an American Tower Structural Analysis Report?
The twist and sway data can be located at the end of the software output within the calculations. If there are no foundation calculations, this will be the last ction within the deliverable. Otherwi, the calculations will be directly preceding the foundation calculations at the end of the analysis.
The output will be titled “Deflections and Rotations.” In TIA-222-G analys, the first load cas within the ction, which are labeled “Serviceability - …” are the important cas. In TIA-222-F analys, the will be labeled “50.00 mph Wind…”. There are four columns; elevation of
equipment (in feet), followed by deflection (in feet), twist (in degrees) and sway (in degrees).
4. Where can the twist and sway data for monopoles be found within the
calculations of an American Tower Structural Analysis Report?
In general, monopole structures will not have significant twist. For this reason, the analysis only gives deflection and rotation values. The rotation value is the same as the sway. The two values are typically found two pages before the end of the software output. They will be in the ction labeled “Load Ca: 1.0D + 1.0W 60.00 mph Serviceability” and sub-labeled “Calculated Forces.”
On this page, the far left column lists the elevation. The cond and third columns from the right provide deflection (in inches) and rotations (in degrees). All other columns can be ignored.
5. Is there twist and sway data on PE letters?
Professional Engineer (PE) letters do not have twist and sway data within the document and do not have calculations that allow for twist and sway data to be extracted. For this reason, PE letters will no longer be completed for Financial Services projects unless specifically asked for by the customer. Otherwi, all rvices will be completed as full analys so that twist and sway data can be calculated and reported. 6. Why are twist and sway values taken from the rvice
ca and not from the full-wind ca?
Using the most recent wind maps from the 2012 International Building Code, wind speeds for the
上海的古镇full-wind cas are developed bad upon a 700-year mean recurrence interval. The wind maps
correspond with the wind speeds ud within our analys after TIA-222 related safety factors
are considered. This level of risk is considered too stringent by TIA-222 for rvice concerns, and
文竹可以水培吗lower wind speeds are allowed. Service-ca wind speeds are generally developed assuming a 10-
year mean recurrence interval. Bad upon this information, the maximum twist and sway values
reported in the rvice cas should only be reached approximately once every 10 years. The
minimum rvice wind speed ud in TIA-222-F is a sustained wind speed equal to 50 mph (fastest
mile). TIA-222-G us a gusting minimum rvice wind speed of 60 mph (three-cond gust).
7. Will twist and sway limits be maintained during other tenant installations?
Twist and sway values will be checked for all Financial Services tenants on any analys
that are completed. If the values are found to be outside of their limits, the tower
我要干网will need to be modified to reduce twist and sway for any existing dishes that are out
of tolerance before installation of new equipment will be allowed to occur.
8. Is there a way to verify that twist and sway limits are being
upheld during other tenant installations?
Current twist and sway values can be verified by ordering a twist and sway analysis from American Tower.
This analysis will provide a report similar to a typical structural analysis and will u the most up-to-
date loading at the time of the order. This offers additional confidence to any carrier that is concerned about twist and sway levels being maintained. This rvice will be similarly priced to a typical structural analysis bad upon all calculations and twist and sway tables being included in the deliverable.
