cable Tensions from P50 sag surveys aug-sept 2020

sept 2020
Links
Intro
Scanning the cables with the p50 laser scanner
Computing the cable tensions from the sag survey.
Results of the tension measurements
Summary:

Updates:

Other pages
Tower4 AuxNorth failure


Intro (top)

    The 305m north Auxmain cable on tower 4 failed on 10aug20 (more info). Felix and I scanned the main and backstays cables aug-sept 2020 using the leica p50 laser scanner.
We scanned one location at a time (t4 main,t8mains, t12 backstays...etc). We ended up scanning each location multiple times to check if the scanning location had an effect on the measurement results.

    After scanning, the data were input (via the leica software) and output  as .las files. A set of idl routines was written to

    Plots were then made of the cable  tensions by location. Tension imbalances in the measurements as well as a imbalances on the towers  were investigated.


Scanning the cables with the p50 laser scanner. (top)

    Measuring the cables with the p50 scanner


Computing the tensions from the p50 surveys.


Results of the tension measurements (top)

Tension plots of individual measurements

Over plotting all measurements by location:

    The cables at each location were measured multiple times from different p50 locations.
This allowed a check if the scanner location had any effect on the measurements.

The tension plots contain:

 Over plotting tower to platform cables (.ps) (.pdf) (top)

processing: x101/p50/cables/plottension_main.pro

Over plotting tower to anchor (backstay) cables (.ps)  (.pdf)  (top)

processing: x101/p50/cables/plottension_bstay.pro


Plotting the average cable tensions (.ps) (.pdf)  (top)

processing: x101/p50/cables/cmpavgtension.pro, plotavgtension.pro

Tension imbalance - platform cables (top)

N/S, E/W tension imbalance on the platform.

    The platform is suspended from the platform cables, and is pulled vertically by the tiedown cables (only t4 and t8 have tension).
Since the platform is stationary (horizontally), the N/S and E/W tensions should sum to 0.

Cable # cables Avg Axial
Force
[kips]
N-S horizontal
component
[Kips]
E-W horizontal
component
[Kips]
Vertical
component
[Kips]
MC04 4 639.8 -312.1 -540.5 140.5
AC04S 1 612.1 -245.2 -550.8 106.1
MC08 4 493.7 -240.8 417.1 108.8
AC08N 1 575.4 -332.8 458.3 101.1
AC08S 1 742.9 -300.1 667.2 128.9
MC12 4 525.5 512.0 -0.0 118.3
AC12E 1 404.5 395.9 41.3 72.3
AC12W 1 720.5 705.5 -71.6 127.2
Imbalance
(sum)


59.8 50.8 2005.9
AbsSum

6239.0 5619.7 2005.9
% err

0.96 0.90


platform hor. tension imbalance (Thorton,single dataset)
Cable # cables Avg Axial
Force
[kips]
N-S horizontal
component
[Kips]
E-W horizontal
component
[Kips]
Vertical
component
[Kips]
MC04 4 630.0 -307.0 -532.0 132.0
AC04S 1 622.0 -249.0 -560.0 100.0
MC08 4 539.0 -263.0 455.0 113.0
AC08N 1 555.0 -321.0 442.0 90.0
AC08S 1 739.0 -296.0 665.0 120.0
MC12 4 551.0 537.0 0.0 118.0
AC12E 1 399.0 391.0 41.0 64.0
AC12W 1 697.0 683.0 -72.0 116.0
Imbalance
(sum)


76.0 208.0
AbsSum

6368.0 5728.0 1942.0
% err

1.19 3.63

Plots were made showing how these 2 tension calculations differed (.ps) (.pdf)

    Looking at the page that over plots the platform measurements   (Over plotting tower to platform cables (.ps) (.pdf)),
you can see that the T8 mains were measured four times (from 3  different locations).
All of these measurements gave main cable values that matched to within a few kips.

processing: x101/p50/cables/balancetwr.pro, cmpthorao.pro, genthortbl.pro


Tension imbalance at the towers. (top)

    The tension imbalance on the towers was computed using the backstay and platform cable tensions.
There are two terms:

The catwalk cables:

    In addition to the platform, backstay cables, each tower has 1 or more cables used to suspend the catwalk.

    Plot of the catwalk cable tensions (.ps) (.pdf)

The table shows the tension imbalance for the radial and perpendicular  forces on the towers.

tower
T12
kips
T4
kips
T8
kips
Notes
radial horizontal imbalance
ignoring catwalk cable
-152.8
-227.4
-220.1
+ is toward
platform
radial horizontal imbalance
including
catwalk cables
46.8
22.3
42.5
perpendicular force on towers
31.9
-62.8
14.2
+ is CCW from
tower/platform line

Summary: (top)

DataNotes:

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