Column Line Layout for Bridge Piers

A lot of times the contractor will do this kind of layout himself.?ÿ How they do it I don't know.?ÿ If I was doing it myself, I would use the first method you described, which is a method I have used to mark the tops of forms before.

Try building a circle poly line then stake to line check the east or west quadrant edge of form then the north or south quadrant and adjust based on the offset.

I already have enough grey hair. I would never take on a bridge layout in that detail - those days and heartburn are over.?ÿ

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Posted by: mvanhank222

Try building a circle poly line then stake to line check the east or west quadrant edge of form then the north or south quadrant and adjust based on the offset.

That's what we do, but we check them at the turn buckles.

I always offer the choice to the superintendent. As far as I can remember they always chose the column to be plumb even if slightly out of position. This is how we are doing it at the moment anyway

I ?ÿtoo use reference line (measure line in Leica Captivate) to measure to points on the ribs of the column form.?ÿ

For a perfectly round object like a pile cage or casing I use grazing sight angle obs to both sides, split the difference, turn the angle and measure a reflector less ?ÿshot on the cl. Calc and reference line the resulting coordinate?ÿ

There are a few shortcuts to do this depending ?ÿon the instrument and software. Or i calc it on a spreadsheet on my phone?ÿ

I donƒ??t think it has to be a cardinal direction just approximately 90 degrees between observations.

I have not done it before.

From the old school perspective I would think that the place to start would be for the builders to tape the O.D. of the form at the top striking a line through the greatest distance, measure the hypotenuse of the associated 45-45-90 triangle and strike another line across the?ÿ can there, use those positions to set their supports and drive a nail at a common feature of the form, tie a string on the nail tape the distance from the top and adjust until the top and bottom are equal.?ÿ

I have seen guys use that approach to plumb wall formwork at about 30' and get it on the money. So it follows that if they started that way it would make the survey work much more streamlined.?ÿ

If the work can be accomplished with a level alone I would try to pass that portion of the work off on the guys. If they can not level around a can and pocket tape to the top it is time they learned, but that is just my opinion.

For the total station work I would probably use a reference line program, although if all you were interested in was the delta to center an easy way would be to just point stake it with the orientation being either "AZ to point" or set up a arbitrary line with zero at the center and a bearing toward the turnbuckle and adjust the top of can until the OD of the form is at station equal to the associated radius. Another tool to keep in hand is to shoot three points on the OD, calc the center and inverse to calculated position.

Most of the marine and bridge guys I have spoken to are wary of Surveyors due to having been burnt in the past, whatever technique I used I would try to be at unity with them by having a check built into the system based on plump line and string or something similar. The stories some of these guys have about poor survey layout are a true disgrace to the technical acumen of many of our peers.

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Thanks for the advice. I also was curious what methods other surveyors use in the field to montitor the can during and after the pour, to ensure that the pole braces dont shift, and the column form remains plumb. I know from past experience that when things are slow, I have the luxury to check it during the pour, but for the most part I'm too busy to babysit and rely on the carpenters, and laborers to keep an eye on it.

If there is a need to monitor during pour the responsibility to do so should be delegated from the top and not dependent on work flow.

In my limited experience pour watch is generally done by visual inspection only and is usually by one of the guys who built the thing.

When I have done it, I used local control for convenience and used point to point inverse to monitor the relationship of the forms on themselves with direction and tolerances as defined by the engineer who designed the system.