Existing Rail Trestle Analysis

[PBW2]

We are looking at a project that will involve the analysis and rehabilitation of an existing concrete RR trestle. The client is requesting an analysis of the bridge to determine the amount (if any) of strengthening that will be required. The trestle appears to be in decent shape but there is some spalling due to the reinforcement rusting.

My main concern is that there aren’t any existing drawings so determining the size and amount of reinforcing will be tricky. There are a couple of approaches:

1. Assume that the bridge is structurally sound and then go in and rehab the portions of the bridge that need it. Not sure if this would fly with the client.
2. Do invasive testing to determine the size and number of reinforcing. Is there a way to do this without partial demolition?

Just wondering how some of you might approach this. Any and all input welcome and appreciated.

 

[msquared48]

Never, but never, assume that there are no other problems with any structure when you can see one or two. If you have to provide a report ennumerating what deficiencies there are and what repairs have to be made, you have to physically check out the entire structure, top to bottom, end to end. This report incurs tremendous liability for you.

If you place limitations on the inspection, then state so in the report, subject to the needs of the client.

Thedre are methods to determine the location and size of the rebar, within certain constraints. There are various forms of non-destructuve testing equipment out there in the market you can check out on the web. One may give you what you need. There are also special testing agencies you can hire. Personally, I would not do destructuve testing unless absolutely necessary, especially if this bridge is currently seeing trraffic.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[JedClampett]

If your client isn't the railroad, then you better touch base with them. If the bridge is not scheduled to be closed, then they're likely to use your project as a way to get a new bridge, not matter what it costs others. And to make it better, they're notoriously hard to work with.
There's almost no way to scope this high enough.

 

[paddingtongreen]

I'll bet your client wants an answer that will place any extra work on your account. Unless your company does this on a regular basis, you need the help of a sub who knows this end of the business; not an easy thing as he would like the work for himself.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[bpstruct]

The FRA recently started enforcing their requirements for privately held railroads to put in place their bridge management program. Part of that includes yearly bridge inspections and load ratings. Not sure if your project is in response to this new requirement or not. But either way, my understanding is that the privately held railroads are not as strictly regulated regarding loads as the highways are. Each railroad can carry loads as heavy as they want as long as they can prove the structural integrity of the bridges. Because of this, I would be very careful as to what conclusions I draw.

I've done a few proposals for these lately, and my proposals are always very clear as to what I will be able to provide and what limitations there will be. My company doesn't do any NDE, but I think there are products out there that will allow you to locate reinforcing and give approximate size. I will say that I have seen reports from a company on another project I did, and I wasn't impressed with the ability to determine reinforcing specifics. I was given "ranges" of locations and approximate sizes of rebar. Then you don't know grade of steel or strength of concrete...still unknowns.

 

[PBW2]

Thank you for all of your comments. I should have pointed out that the project is actually a rails to trail project. The trestle, in reality, will only need to support pedestrians/cyclist; however, the owner wants the trestle to also support a 72,000 GVW emergency vehicle (fire truck maybe). We are going to try and farm out the analysis/retrofit of the bridge because of the unknowns. The RR no longer owns the land and all of the rails have been removed.

Thanks again,

PBW2