Main cable catenary measurements mar06
jul06
The catenary sag for the main cables was
measured in mar06. The table below shows
-
The cable name
-
The date and time when each of the catenaries were measured.
-
The total tiedown tension at each measurement (averaged 5 minutes around
the time supplied by felipe).
-
The az posiition (dome side), dome position, and carriage house position
for each measurement.
|
Cable
|
Date
|
Time
|
total Kips From Td's
(by Measurement)
|
az pos
(dome side)
|
Dome pos
|
ch pos
|
|
M-8-1
|
3/17/06
|
2:19 p.m.
|
37
|
270
|
8.5
|
8.8
|
|
M-8-2
|
3/17/06
|
2:43 p.m.
|
37
|
270
|
8.5
|
8.8
|
|
M-8-3
|
3/17/06
|
2:59 p.m.
|
39
|
270
|
8.5
|
8.8
|
|
M-8-4
|
3/17/06
|
3:30 p.m.
|
79
|
270
|
8.5
|
8.8
|
|
M-8-North
|
3/17/06
|
4:02p.m.
|
84
|
270
|
9.0
|
8.8
|
|
M-8-South
|
3/17/06
|
1:40p.m.
|
34
|
265
|
8.5
|
8.8
|
|
|
|
|
|
|
|
|
|
M-4-1
|
3/18/06
|
11:29 a.m.
|
68
|
270
|
10
|
0
|
|
M-4-2
|
3/18/06
|
11:56 a.m.
|
62
|
270
|
10
|
0
|
|
M-4-3
|
3/18/06
|
12:24 a.m.
|
63
|
270
|
10
|
0
|
|
M-4-4
|
3/18/06
|
12:48 a.m.
|
57
|
270
|
10
|
0
|
|
M-4-North
|
3/18/06
|
10:48a.m.
|
79
|
270
|
10
|
0
|
|
M-4-South
|
3/18/06
|
1:18p.m.
|
62
|
270
|
10
|
0
|
|
|
|
|
|
|
|
|
|
M-12-1
|
3/23/06
|
11:42 a.m.
|
62
|
270
|
10
|
8.8
|
|
M-12-2
|
3/23/06
|
1:17 a.m.
|
62
|
270
|
10
|
8.8
|
|
M-12-3
|
3/23/06
|
1:35 a.m.
|
67
|
270
|
20
|
8.8
|
|
M-12-4
|
3/23/06
|
2:10 p.m.
|
67
|
270
|
10
|
8.8
|
|
M-12-West
|
3/23/06
|
11:06a.m.
|
67
|
270
|
10
|
8.8
|
|
M-12-East
|
3/23/06
|
2:34p.m.
|
70
|
270
|
10
|
8.8
|
Average tiedown tension: 61 kips (averaging over all cable measurements).
What was going on during the sag measurements:
You can compute the tensions in a cable from the sag
measurements. When doing this you need to know the position of the
azimuth, dome, carriage house, and the tiedown tensions when the
measurement was made.
The tiedown tensions are recorded using load cells
as the connecting pins for the tiedown jacks. There are two tiedown cables
at each corner of the platform (the reported tensions are the sum of these
two cables) . The load cells are read once a second and recorded on disc.
Four plots were made for each measurement day. They
included:
-
The azimuth position versus hour during the measurements
-
The gregorian dome za during the measurements. The ch was left at a constant
za for each measurement day.
-
The position (linear pull down) of the tiedown jacks during the measurements.
-
The tension (from summing the two cables at each tiedown) at each triangle
corner during the measurements.
-
Color coded dashed vertical lines were placed at the times when each cable
was measured.
The bottom two plots use black (td12), red
(td4), and green (td8) to distinguish the
positions and tensions for the 3 tiedowns.
The plots show the
tiedown tensions and az, za positions (.ps) (.pdf):
During the measurements some things were moved:
tower 8
17mar06
dome za=8.5
ch za=8.8
|
15:18
|
auto tracking of tiedowns with distomats turned on.
Jacks moved by 8 inches
tensions at each corner increased by about 8 kips
Affected cable measurement M-8-4 and M-8-North |
| 15:54 |
az moved 270-> 266
greg za moved 8.5->9 deg
affected cable measurement M-8-North |
|
tower 4
18mar06
dome za=10
ch za=0 |
Looks like the auto tracking of the tiedowns was left on.
Jacks moved by about an inch during the measurements.
Tensions were higher than tower 8 (20 to 35 kips in the 3 cables). |
tower 12
23mar06
domeza=10
ch za=8.8
|
13:42
|
Dome moved to za of 20 degrees
This affected cable measurement M-12-3
The tension in corner 12 only changed by 1 or two kips since
the az was perpendicular to tower 12.
Corner 8 lost all tension while corner 4 increased by 20 kips.
This motion may have caused the platform to slide horizontally a little
toward tower 4. |
| 14:00 |
Dome moved back to za=10. |
The auto tracking of the tiedowns was left on.
The jacks moved by about an inch during the measurements. |
The carriage house was moved to za=0 for cable 4 measurements.
It was at za=8.8 for the other two cable measurements.
processing: x101/060317/tdcatenary.pro
home_~phil