Big Steel Question

Bolt Plate?

Isn't there a plate with bolt holes welded to the top end of the wide-flange column?

I assume that what a designer will be mainly interested in would be the centers of the bolt plate and the pattern of the holes in it. Presumably, you'd be asked to verify that the centerlines of the plate are coincident with the centerlines of the column, too. Probably the best answer is to ask the structural engineer.

Bolt Plate?

No plate. Just the end of the I-beam. To quote the structural guy:

What we need to accomplish is tying down the spacing of the grid to design the new beams from. So, one shot for each column that establishes the center of each column should be sufficient. Again, what is important to us is assuring the new beams are fabricated to the correct lengths. So, we need to make sure the column spacing is correct.

I do not know how much variation one finds in structural steel for buildings, but I know the steel I've worked with in transit applications varies dimensionally by an amount that surprised me one time.

Where's Scott Z. when you need him?

Bolt Plate?

If thats the case then I think measuring diagonally strike a line, then the other diagonal will give you an "X" at the center.

I would ask very specific questions about amount of details and accuracies desired. For instance, are they concerned about the orientation of the beam? Are they concerned about if the beam was cut off square? Are they concerned about the dimensions of all elements of the beam? Are they concerned about verticality?

Mike Falk is someone you ought to ask as well as Scott.

Bolt Plate?

I've never done anything like this before.

I would take my pocket tape and make some sort of station mark in the center of the I (maybe use a center puch if it'll dent the steel).

Then turn sets through all the I-beams. This is probably one time I would do redundant observations on a topo. Turn sets through all of the station marks from at least two setups and adjust it all in LS.

I would probably single observe the ends of the flanges (four shots per) just for fun from each setup too.

Measure Wide Flange Section

Well, if there is some question about the variations in the dimensions of the sections, you'd need to supply those measurements. I'd think (i.e. speculate) that you'd want to probably put a punchmark on the web of the column at the center of the section, i.e. midway between the flanges on the centerline of the web, and that a simple tape would work just fine for that.

Then, you'd record the dimensions from the punchmark at column center to the outside faces of the flanges and the web thickness, and finally get enough redundant shots on the column centers to have them located well under tolerance.

The question would be, how does the engineer propose to attach the new columns to the lower ones?

Is he going to design a bearing plate, or is he going to splice them together?

To cover all eventualities, I'd locate the four outer corners of the column, and then locate the central point on the web.

I'd also get the thickness of the flange and the web, as these may not always be what the original plans call for.

Angelo

Without know much about this type of work... er... ah... knowing much at all... That looks like a 6-shotter to me. Maybe use a hand tape to get it all lined up and def a sketch for widths and such. That is a great place for a plumb bob and peanut or a very short pole. Punch mark and a Sharpie too.

I'd have a heck of a time with my little bi-pods and robots with that arrangement.

At first blush I like Angeto's answer but I also would follow Dave's recommendation to ask many questions, for clarification of the data needed.
jud

My experience with this type of location is very similar; however, there was a bearing plate already welded to the beam. You should already have an existing column grid with inter-column dimensions. What we did was to establish the plan grid for the columns horizontally by turning 90's and pulling chain with tension handles and temp corrections. We then set up on each column line on two sides of the network and established line points on each side of the bearing plate; having established line in both directions on each plate, it was then a simple matter of measuring the offsets from column lines to all four corners and the center of each bearing plate. We then established elevations on all four corners and the center of each plate to the 1/2 hundredth (1/16"). I have found that in high accuracy as-built situations where there is a plan grid, that this is the best method of acquiring and reporting results.

RRain

P.S. We had the luxury of being able to see down onto the surface of almost all of the bearing plates.

Nobody is saying anything about 'scanning'???

DDSM
(what do I know...my 'tape' is graduated in links):beer:

Shhhhh! We don't need (have) no stinkin' scanner!

Thanks for all the info. I will be getting with the steel engineer on Tuesday to refine the scope.

Bolt Plate?

When I did this kind of surveying, we would setup our working baseline by measuring from a corner of the existing beams.

We would adjust our offset staking distances to center line of beams by taking measurements of the existing and new beams to assure their centers would align together.

When we would layout the string lines for the new pours for bolt positions, we would stake the actual center line of the bolt patterns and the carpenters would make a jig that would position the bolt patern.

It ain't Rocket Science, when in doubt measure as much as you can!
Done many retrofits. Get with the steel detailers ask him what he wants and then give him anything you think he will need additionally. For us it's usually a guaranteed return trip. They never really know what they need until they find out it's missing.
Ralph

We would use a jig that would allow us to acquire x,y,z on all four corners.

Mr. Falk

I see you are just joining us.

Welcome. I think Andy got that one figgered out 😉

Carl