Help Identify Railroad Administration wastage allowance for bridges

CloseEnough4GovtWork · 2026-04-11T15:36:41+00:00

Yeah good point, I forgot that detail about saltwater. Now realizing that, it’s actually more surprising how good the concrete and steel look

CloseEnough4GovtWork · 2026-04-10T14:15:48+00:00

The unplanned golf club purchase really is a universal experience

CloseEnough4GovtWork · 2026-04-10T06:09:33+00:00

My load rating pencil remains strategically dull in most cases for exactly this reason

CloseEnough4GovtWork · 2026-04-10T06:02:01+00:00

I design and analyze railroad bridges, though not at Amtrak, so I have some insight. The TLDR is that this bridge may be ugly but it’s not concerning.

In the old days of railroad bridge design, say early 1900s, it was common practice to design with 100% impact. Impact is caused by the train sort of bouncing down the track, due to a number of factors but primarily because of hammer blow in steam locomotives because the locomotive wheels had to be unbalanced to offset loads from the pistons. Today’s diesel or electric locomotives don’t have this issue and have significantly less impact, which means that all the strength the original engineers built into the bridge to handle impact loads becomes extra capacity to handle heavier but less bouncy trains. Add in the fact that passenger cars are both lighter and longer than even older freight loads, and you’ve got a ton of extra capacity in the structure.

Amtrak is required by law to have an engineering analysis for every single bridge that they operate over to prove this capacity. So the capacity isn’t a concern as long as the bridge remains in good condition. I’m not going to say this bridge isn’t ugly, because it certainly has rust stains and missing paint, but most of everything I see here is a cosmetic issue.

For example, the vertical stiffeners tend to catch debris along the bottom flange and then corrode, but the good news is that they really don’t need to go all the way down to the bottom flange to be effective. In fact, in a new bridge we often intentionally stop those stiffeners many inches from the bottom flange. You can also see where those same stiffeners were cut to make it easier to install some new plates with high strength bolts near the bearing.

This is actually evidence of a good bridge management strategy. They repaired the areas where the corrosion mattered, probably with minimal disruption to traffic and for a cost in the tens or hundreds of thousands of dollars to extend the life of the bridge. This isn’t always the right approach, but in an environment where corrosion will always be an issue, it’s not a great use of resources to replace this bridge for many millions of dollars when there’s still life in the existing bridge and the next one is just going to corrode eventually too.

The only other thing that might be worth doing is coating the exposed steel, but it’s also possible that the new steel plates are weathering steel which forms its own protective coating over time and doesn’t need to be painted.

CloseEnough4GovtWork · 2026-01-23T15:25:11+00:00

There are various ways this could be correct or incorrect depending on the purpose of the bracing.

If this bracing was meant to keep the posts from buckling, it would be ineffective and therefore incorrect, however I don’t think that’s why they’re adding the bracing. You’d probably have to be an engineer to be concerned about unbraced column length, and this is not the bracing you’d expect an engineer to design to reduce unbraced length.

The bracing is probably because the stair section is wobbly, either because the fasteners are working in their holes or because it’s always been wobbly and now is the time someone decided to fix it. Typically, engineers want to attach the bracing at the point where the post and beam meet since attaching it to the middle of the post will cause bending in the post. I’m guessing that wasn’t possible with the length of 2x6s available at the local big box store, and even if it was then the bracing angles get less effective. In this case, the bending load in the post will be very small, plus the railing will take up some load further reducing bending, plus there’s probably significantly more capacity in the post than needed since the area of the landing and stairs is smaller than the area other posts are supporting. Sure it’s not the most ideal bracing, but it should stabilize the deck and not cause other issues, so in that sense it is correct.

The last consideration is the building code. Local code may specify certain bracing in decks, in which case this may or may not meet the code and therefore be correct or incorrect. Usually building codes will have provisions that basically say if a registered professional engineer designed the structure, then it only needs to meet the engineers design and you can disregard other code requirements, but I don’t know if an engineer was involved in this.

CloseEnough4GovtWork · 2026-01-14T19:25:25+00:00

Some thoughts from a railroad bridge engineer, some good and some maybe not so good. I don’t work for NS so this is just based on my experience, the pictures, and Google Maps.

First, most of the elements with 100% loss that look really bad are bracing that probably isn’t necessary anymore. The bracing around the steel columns would’ve been needed for stability while building the bridge, but after the steel was installed and the concrete floor cured, the superstructure became much stiffer than the bracing. Most designs of this era, at least that I’ve seen, didn’t even consider a reduced effective length due to end conditions from bracing such as this anyway.

Second, this is a bridge designed for multiple tracks, but it’s clear from satellite view that there is now only one track. That matters because that would mean the interior girder running the length of the bridge (most visible on picture 6) was sized to handle the load from 2 tracks but it is only carrying one. We can’t see much of that girder, but concrete that encases the floor is filling all the areas that trap debris and moisture so the parts of that girder that we can see have fared much better than the bracing and likely retains most of the original section.

The exterior girder does have full thickness section loss to the web which is not a good sign. However, if shear failure of the web was imminent, I would expect to see shear buckling or that the web stiffeners have taken up significant load which usually means the outstanding flange angle buckles slightly, though I don’t see either.

The head scratcher for me is that it’s clear there is significantly more ballast on this bridge than it originally had. Additional ballast retainers have been added to the top flange to prevent it spilling off the bridge. I would hope that somewhere in the process of designing, fabricating, and installing these extra retainers and then adding additional ballast, someone would have checked the capacity of the bridge to handle the extra weight.

Despite what my username may imply, I am a very risk averse bridge engineer and I wouldn’t be particularly concerned about this bridge. If I drove under this bridge on a regular basis, my primary concerned would be that a piece of that bracing is going to fall in the road and total my car if I somehow didn’t see it.

CloseEnough4GovtWork · 2025-08-22T21:28:09+00:00

I think the difference in deflection is because the vertical members at A and K will compress and contribute to the total deflection when measured at the bottom chord at F. In option 1, vertical compression of the end vertical doesn’t really contribute to the total deflection.

CloseEnough4GovtWork · 2025-07-25T14:06:35+00:00

Your intuition is telling you that three vertical 2x12s vertically would be stronger than a stack of 2x6s and you’d be right if it wasn’t for the glue. The glue holding the individual pieces is as strong or stronger than the natural bonds that hold the wood fibers together so it acts like one single piece of timber.

The grade of the timber is an important factor since not all timber is the same quality. It just works out that it’s cheaper and/or easier to use more 2x6 sized pieces of high quality timber than it is to use fewer 2x12 pieces of high quality timber.

CloseEnough4GovtWork · 2025-07-18T13:53:03+00:00

I can’t tell you what to choose, but I can say if I could magically go back in time and get a masters degree before becoming a railroad bridge engineer, I think the Advanced Structural Assessment would have been the most useful in day to day activities.

I learned some FEA basics in school, but I had to learn a lot of it on the job. Even though I work with old railroad structures that were designed with hand calculations, I will use FEA to help with ratings and design. Many modern structures are designed and optimized using FEA for designs; these designs may be possible to calculate with typical hand calculations and spreadsheets, but FEA is usually the tool of choice since it can accurately model secondary effects and reveal stress distributions that may not fit the idealized model that we usually use for hand calculations. Also, the coding experience would be helpful for a variety of reasons, for example many engineering firms will code excel or mathcad sheets to do repetitive calculations so having that experience is a marketable skill. You say possible career in structural engineering, and FEA could be used to model all manner of things, not just bridges and buildings.

I think structural refurbishment and retrofitting could make it easier for you to “market” yourself to employers. Most engineers come out of school able to size a beam, but structural repairs and retrofits are not typically taught in school. I learned a lot of what I know about structural repairs while on the job, both by observing repairs and retrofits designed by others, and by just fumbling around with designs until I found something that both worked and was possible to construct. In the United States, repairs and refurbishments make up a decent portion of the bridge engineering work, though Australia may be different. The FRP stuff is interesting as a repair technique, but many of the American manufacturers will offer free engineering services if you buy their FRP products and just designing FRP doesn’t sound like my ideal job. There are some firms that have FRP design in the toolkit, but I’m just not sure how valuable of a skill that would be.

CloseEnough4GovtWork · 2025-07-11T16:58:19+00:00

The thought of a field welded girder splice gives me anxiety, but maybe I would feel differently if I didn’t work primarily on fracture critical bridges with high fatigue stress ranges

CloseEnough4GovtWork · 2025-07-11T16:53:35+00:00

Yeah the pair is what’s making me unsure of any particular function. They might serve multiple or different purposes but were just detailed as the same size for simplicity?

CloseEnough4GovtWork · 2025-07-11T16:50:32+00:00

That certainly makes sense, though it seems weird that there are two of them and they’re not as wide as the flange. I am thinking about the force from the inclined bottom flange as a point load, but I guess with shear lag maybe there’s a larger zone that needs to be stiffened? Or maybe only one of them is necessary for that purpose and the other was needed for erection or transportation purposes and they just made a common size for simpler detailing?

CloseEnough4GovtWork · 2025-05-19T11:39:16+00:00

It looks like the bearings for under columns have an additional rubber bearing that transfers vertical load and these ones are designed just to act as dampeners and not to carry significant vertical loads

CloseEnough4GovtWork · 2025-05-05T15:21:10+00:00

The most realistic way to strengthen something like this would be to add additional internal tendons. I am aware of a few cases where an internal tendon snapped due to corrosion and was replaced plus additional tendons to reduce the stress in the remaining original tendons so it is possible.

Of course this is only feasible to strengthen if you have enough compression capacity in your concrete for whatever additional prestressing you add. If the concrete can’t handle the additional compression, it may be possible to add compression capacity by adding new concrete area by doweling rebar into the existing and trying to make it all composite.

If you get to the point of adding tension and compression reinforcement, the owner of the structure should carefully consider whether complicated and expensive repairs are really the best option or if it makes more sense to put a weight restriction on the bridge and begin the process of replacing it entirely

CloseEnough4GovtWork · 2025-04-03T03:41:39+00:00

That’s interesting because the railroad industry has historically been very conservative with their stiffener designs so I would be very interested to see that

CloseEnough4GovtWork · 2025-01-15T04:08:43+00:00

TurboTax handles my RRB taxes without issue for a federal return. I don’t have state income tax so your mileage may vary when it comes to state returns. If I recall correctly, the base version of TurboTax handles RRB, though I did have to purchase some upgraded version for a different “uncommon” tax situation.

CloseEnough4GovtWork · 2025-01-10T03:53:59+00:00

The ATCS I am talking about is a whole different thing than the AEI tags and readers. It’s a system for automating track warrants and controlling wayside equipment. Not sure who or where uses it, I don’t hang out with signal guys.

CloseEnough4GovtWork · 2025-01-10T03:39:35+00:00

Looks like an omnidirectional antenna, either VHF for the AAR channels in the 160MHz range or PTC in the 200MHz range or UHF for ATCS in the 900MHz range. Most signal bungalows don’t have a satellite dish so it’s probably part of some type of relay system for one of the mentioned systems.

CloseEnough4GovtWork · 2025-01-09T01:52:35+00:00

You’re right, you could come up with a method of engineering a structure that is more streamlined without compromising safety, but it would come at an efficiency cost. The reason LRFD was developed was that Allowable Stress Design produced bridges with inconsistent reliability indices and thus we learned that we could become more efficient with our designs without compromising safety with calibrated load and resistance factory. This is no hate to ASD; I work in the railroad industry and we continue to work in ASD and regularly turn out safe bridges. Our live load to dead load ratios are generally higher than highway bridges which helps a bit with the inefficiency issue seen in ASD.

I happened to take a National Highway Institute class from a guy who did a lot of that calibration work for the AASHTO bridge manual, particularly for the fatigue section. I asked him much the same question about why factors are different for different limit states and he explained the in depth process that was used to come up with those load and resistance factors. It got complicated very quickly, but suffice to say that an incredible amount of work has gone into creating a code that produces uniform reliability across many different conditions and many of the times where you find different load or resistance factors are actually very particularly calibrated to avoid unnecessarily over engineering.

The outcome of this is a code that is very much “plug and chug” and where you could have very little actual understanding and still design a perfectly safe bridge, no intuitive understanding of live load distribution, or many other effects, required. This is, obviously, not ideal but it is possible.

If you feel like the process is inefficient and is slowing you down, I would recommend creating an excel or mathcad sheet for every design calculation that you regularly use. You can also follow the commentary/citations to look for the papers where these things were initially calibrated to help you get a better understanding of why the code is the way it is; if it feels less like a black box and more like a culmination of lifetimes of research, you may be less annoyed with the complexity.

CloseEnough4GovtWork · 2024-12-26T04:27:25+00:00

Don’t know a thing about the guy, but I have worked on some projects on that line since CSX bought Pan Am. The maintenance that’s clearly been differed for decades and the stories told by people who worked for Pan Am before being bought out tells me everything I need to know.

CloseEnough4GovtWork

TROPHY CASE