With spec's like that, you'll need to be onsite for the entire erection?ÿ ??ÿ
I can imagine it moving more than 0.21 ft under working load or wind.
Before the cab and jib are attached to the top it should stay plumb. If there were high winds then the erection would stop, and yes - measurements would be pointless.
As Lee says, it needs to be right at the bottom. I wasn't aware there was anyway to adjust the mast as it is erected. Can be checked though if they want peace of mind.
Once the cab and jib and counterweight is on then it will tilt heavily backwards, progressively going forwards when the crane takes up the weight of a load. Worst case is always backwards - the counter weight is the biggest load the crane will take.
Have used reflective targets to measure the extent of movement once when the crane driver was concerned that it felt too flexible.
The advantage of prisms is that you can make a much steeper sight. This is also helped by the ability to use autolock. It's a handy option - a telescope camera or diagonal eyepiece could also be used, but so many instruments have autolock it seems to be the easiest way. If you can get prisms fixed up there. I wouldn't fancy doing it myself.
Sqouwse is correct.?ÿ
Mark you mentioned on phone that your crews do not have a robotic total station. It will be extremely difficult, if not impossible to site an object at a steep vertical angle without auto tracking, you need an adapter and may have to remove the handle from the TS. Even with the right angle adapter it is a real pita going up and down the height of tower.
Sounds you may not have proper equipment, with no experience in this. You are taking a bug risk. A recipe for disaster! As shown in link above, Erecting the crane cost more than $50,000. That's all labor and equipment cost. If your crews are holding up the erection, you may get a back charge.
?ÿ
We do it as Lee described every time the tower 'jumps' up sections. Job shuts down, crane climbs, we check plumb, #'s signed off on by DOB, PLS, Super & crane company if in tolerance. Site opens & back to work. Last one was 750'?ñ so a 90?ø eyepiece was needed, PITA is what it was as jumps were always @?ÿmidnight'ish and always when it was when weather was worst of that week.?ÿ
We always use a 1" with EDM set to finest mode, & <3 shots to each point to make sure we're shooting what we think we are, no outliers.
?ÿ
One other aspect is that as the building goes up, if you have your axis lines set on the floors, you can use them to read the crane, instead of being on the ground.
We are currently checking several cranes in NYC, including one at 59 stories, eventually going to 82 (950 feet with a 200 foot spire at the top).
AJF
Side shot at FL/GA....................loveable??????? ?ÿReally????????
Lee - what is the easier method? We all want to know 🙂
A four foot level taped to a 10' 2x4?
Lee - what is the easier method? We all want to know 🙂
A four foot level taped to a 10' 2x4?
I work directly for a concrete contractor. We sub out the erection of our tower cranes to the crane company, but are required to monitor it ourselves. If you are monitoring only, then all you have to do is shoot elevations on the legs of the crane and monitor only those marks. That is all that is required. If you attempt to monitor plumpness of the entire structure, you will find it moves all over the place.
I work directly for a concrete contractor. We sub out the erection of our tower cranes to the crane company, but are required to monitor it ourselves. If you are monitoring only, then all you have to do is shoot elevations on the legs of the crane and monitor only those marks. That is all that is required. If you attempt to monitor plumpness of the entire structure, you will find it moves all over the place.
That is exactly how we are doing it.
?ÿ
After talking to everyone involved, we decided that the top of the crane will move way more than our limit so we are monitoring the four corners of the tower/ anchor bolts by simply using a level with a metric rod and reading millimeters.
Hit the bottom on a flange and the top on the same flange reflectorless.?ÿ That's how I've done it.?ÿ Tower cranes can easily sway as much as you describe when loaded.?ÿ Make sure boom is in basically the same orientation at each check.
Following along on this thread, have any of you done monitoring of the outside?ÿAND the inside of a building?
The outside seems straight forward with proper control and targets but a potential client also wants to monitor displacement inside existing structure at existing columns and walls.
John
Following along on this thread, have any of you done monitoring of the outside?ÿAND the inside of a building?
The outside seems straight forward with proper control and targets but a potential client also wants to monitor displacement inside existing structure at existing columns and walls.
John
You should probably start a new thread topic.
