Deck Grades

joabmc, post4, member: 10395 wrote: I'm curious as to how others calculate and shoot deck grades? Almost all of the clients we work for don't like the 10ths marked as the angle comes in 10' sections. They'd rather have 10' stations marked instead. That's fine but it always takes much more time to calculate as 10ths are normally a given and 10' stations are not.
To accommodate the client, I have to build the vertical profile, a cross-slope template and interpolate grades. I've almost perfected a spreadsheet that will calculate the camber on a parabolic curve. We then import all of our finish grade data on one sheet and then populate individual sheets for each beam in Excel. I also shoot all of my existing beams robotically, store each shot, download and populate as well. After everything is populated, I let the spreadsheet run the numbers, verify deck thickness and haunch numbers are to specs.

We've had several discussions over the years about field verifying camber after placement of beams. Inspectors will say to just stretch a string and measure midspan. There is no way IMHO that one will get an accurate read using this method. Anyone have a better one? I've thought about getting a laser to verify? Something that could be attached to the side of the beam and then calibrated to the other bearing. Once calibrated, my thought was to measure at midspan using a stick tape to "field verify" I'm asking because we recently shot a 100' single span and I have a hunch that either more camber came out upon placement or the table is incorrect. When we ran the numbers, we had .25 more concrete at midspan than was listed but were within .02 at the bearing points. We know the beam seats are correct and have been verified. So that isn't the issue and as mentioned, the thickness over the beams at bearing are correct.

It currently takes me between 4-8 hours to calculate the grades and build the spreadsheet depending on the size, number of beams and spans. And it takes between 2-6 hours to mark, shoot, download into my laptop and then mark the beams in the field.

All ideas are welcome.
Thank you.

I would build a 3d surface model and have it in DC to perform real time verifications. My DC software will create the spread sheet for each shot compared actual vs. theoretical.

leegreen, post: 335786, member: 2332 wrote: I would build a 3d surface model and have it in DC to perform real time verifications. My DC software will create the spread sheet for each shot compared actual vs. theoretical.

Can you elaborate? Are you saying a model of the deck or each individual beam? If it is a model of the deck, how do you compensate for camber loads? Each beam is rated differently and more or less will come out as the pour occurs. I can see a model giving you the deck at face value but not being calculate a 2 step process. If it were a model of each individual beam, I'd think That would be a pretty daunting process and you'd almost have a surface for every beam. I'm asking because I don't completely understand how this would be achieved?

joabmc, post: 335791, member: 10395 wrote: Can you elaborate? Are you saying a model of the deck or each individual beam? If it is a model of the deck, how do you compensate for camber loads? Each beam is rated differently and more or less will come out as the pour occurs. I can see a model giving you the deck at face value but not being calculate a 2 step process. If it were a model of each individual beam, I'd think That would be a pretty daunting process and you'd almost have a surface for every beam. I'm asking because I don't completely understand how this would be achieved?

We model the no load for each individual girder on the Bridge. And we also model the super load for each steel girder.

leegreen, post: 335798, member: 2332 wrote: We model the no load for each individual girder on the Bridge. And we also model the super load for each steel girder.

So once this achieved, you are shooting and marking realtime? That does sound efficient. How much time is spent building the surfaces? And does your state require reports to be submitted?

We are using a two person crew, we work in real time shooting and marking. We are also logging data for the report. They would already have a spreadsheet for the girder camber to start from.

I will be in the field now, so will not be able to come until later.

leegreen, post: 335803, member: 2332 wrote: We are using a two person crew, we work in real time shooting and marking. We are also logging data for the report. They would already have a spreadsheet for the girder camber to start from.

I will be in the field now, so will not be able to come until later.

We do the same as Lee. Model the deck with the camber in it and shoot it . We shoot the 20 pts. because it typically comes out really close to where the panels sit. We do not mark them out prior but use the stationing on the girder lines as our reference. We also drop the surface down to bottom of deck just to take that "math" step out of the equation for the guys cutting the foam. The fills that we give them are actually what they have to cut.

Our field engineers verify the camber at the casting yard before they hit the road. I believe that a string and stick rule is their tool of choice.

Sorry, had to run earlier. Looks like my speech to text garbled the last message.

Intended to so say. We generally work with the bridge engineer. They will provide us a spreadsheet of girder camber to start from.

Like roadhand said, we also use 20th points.

leegreen, post: 335858, member: 2332 wrote: Sorry, had to run earlier. Looks like my speech to text garbled the last message.

Intended to so say. We generally work with the bridge engineer. They will provide us a spreadsheet of girder camber to start from.

Like roadhand said, we also use 20th points.

Thanks for the info. PENNDOT is a different animal. We have to calc. the cambers. The camber rating is provided but we do the leg work. Nothing is provided. The Dept want the 10ths marked or will accept 10' stations. The stations work better for the contractor in most cases. Once beams are marked (stations) and shot, calcs. are done and then we mark the cuts/fills to bottom of deck pan or top of angle depending on how you look at it.
We then have to generate a spreadsheet that is sent to the contractor and forwarded to the department for approval. Once approved, the contractor may start welding the angle.
This is PA and as the nation knows, we have thousands of bridges that are deficient and are up for replacement. It's a very hectic environment right now and efficiency is key. The current P3 guidelines want 500 a year for the next 3 years and those are only the ones that are condemned. Another issue is that the plan quality keeps declining at a rapid rate. More and more information is missing. The drafting is bad and often is a copy and paste. So the picture that you are looking at may not even be the bridge your building?!? The one I recently had trouble with lists no dimensions. Just codes that you can reference on a table of variables sheet. The only finished deck grades provided were at the bearings! Camber table was on a separate sheet. To top it off, the bridge is at the end of a horizontal curve so half of the deck is still in a super transition while the profile is in a vertical curve. We are actively working on 27 different bridges ranging from single to multiple spans. I believe my current method is pretty foolproof but like the idea of modeling. I'm just not sure if I have time to experiment with it under our current workload. I would like to here and learn more about it though. I have never built a 3d model on a parabolic curve and I'm sure it would take some time to figure out.