Building to Bridge Engineering 1

[TimmyH76]

Hello all,

I have been doing structural engineering for buildings for ~6-8 years. I have recently been considering moving toward bridge engineering. I have a PE. The architects are killing me!! Any thoughts from others structurals. How hard would the move be? Good idea bad idea???? Thanks for the input.

 

[hokie66]

I have little experience with bridges, but if architects are driving you mad, another area you may wish to consider is industrial structures, where you can be your own architect. But then the mechanical engineers will drive you mad.

 

[cvg]

go into bridges and highway structures and you will be working for nothing but engineers. (roadway and drainage engineers...) Get ahold of the AASHTO bridge design manual to get an idea of what is involved

 

[BRGENG]

I made the switch years ago, piece of cake. You will love it, no architect’s, no all nighters, no last minute changes and you will actually get to see your family. Plus unlike Architect’s you typically won’t have to fight your clients to pay you and the fees are much, much higher. Wait now everyone will want to switch, strike what I said earlier, bridges are hard and you will never make it.

Starting with a DOT is the easiest way and after a year or two consultants will hire you away at a respected salary. Good luck.

 

[msquared48]

If you decide to make the change though, don't burn your bridges.

Sorry, I couldn't resist.

Mike McCann
McCann Engineering

 

[abusementpark]

I am pretty young and made the switch from bridge to building in very short time, but here is what I disliked about bridge work.

-AASHTO LRFD Manual is a beast. Have you ever seen it? It's huge. There's no way possible to get a firm grasp on the equations in the steel section. Each equation has about 10 different variables that need to be determined from other longer, iterative equations. Long story short: you will flip through the whole steel section just to successfully complete one equation. Basically, as I was once told by someone with the DOT: you better have some good computer programs if you want to use this code. For a young engineer, I hated being so heavily reliant on computers to do my analysis for a bunch of code equations that it was hard to get a good physical grasp of.

- Bridge work also involved a lot of number crunching. It seemed to me like less of an art form. Everything pretty much has a set process and solution. Once you have done one typical prestressed concrete girder bridge, you have done them all, etc.

-Also, the DOT has a too tight a grip on you. They are very restrictive about what should be used and what's acceptable, which is probably a good thing for QC, but ties back into my claim of one process, one solution.

The main thing for me was the new AASHTO LRFD. I used AASHTO standard specs for a brief period and might still be giving bridge a chance if that were the current code. Also, I am young so I haven't had to deal with architects directly yet, so my opinion may be changed pretty quickly once that happens. I am started to see how much it sucks to work with sloppy architects. Can anyone highlight the pros/cons of industrial work?? lol

 

[Grizzman]

Design build: Work for the contractor. Let them deal with the Architects.

 

[strguy11]

I made the switch about 4 years ago, and now design both bridges and buildings on a regualar basis. The AASHTO code is a beast, and depending on whether your state DOT does LRFD or not, it can even be more confusing. Most DOT's have design guides/bridge design manuals that assist in the process, but again, the analysis is sometimes tricky. There are some good design books out there, just make sure you buy the one that will suit your particular DOT.

What I dont like about bridge design is the seemingly slow process of DOT review and approval, at least in my state. I also dont like dealing with Right of Way issues, that always come up with bridge design. If you can stay inside a box and just design the bridge, and have others worry about the other stuff, it would be great, but working this way is not practical. Also, you have to get familiar with issues such as line of sight, roadway safety, and the geometrics of roadway layout to be effective. None of which is difficult, however, they are important concepts to grasp, which can affect your bridge design widths. Also, bridge roadway surfaces normally aren't flat, and are usually built to a vertical curve profile which much be determined so that screed elevation can be given to the contractor which account for the DL deflection. Again not too difficult, you just need to understand what is going on. You may also find yourself doing quantity takeoffs for all of your bridge designs, which is normally not done for buildings, as most DOT's require quantities on the plans.

Fees are usually better than dealing with Architects, so that is a big plus.

 

[HgTX]

In my brief time in bridge design (I'm still with bridges, just not design), what I found most interesting wasn't the number-crunching aspect of sizing members, but the challenge of making something fit in limited space, dealing with the existing structure in a widening, figuring out how to handle layout in a flaring ramp, that kind of stuff. Like someone else said, once you've done one prestressed concrete overpass, you've done them all, but where an engineer's mind is really needed is the stuff that's not so ordinary--which comes up all the time.

If your joy is doing math, it may not be the field for you. If your joy is solving 3-D puzzles in your head, it may be.

I'd think that someone with building experience wouldn't be any less hireable than a new graduate with no experience, but I'm no authority on the matter.

Hg

Eng-Tips policies: faq731-376

 

[jorton]

I have to agree with HgTX. I spend WAY more time dealing with geometry issues than I spend performing structural calcs for each bridge. It is even more fun on urban jobs.

 

[abusementpark]

I would also like to agree with others above some bridges being a geometric nightmare when you have a parabolic curve governing the elevation and a radius defining the horizontal layout. It seems like majority of the plans get filled with geometric details, such as a riser elevations to four decimal places. Quantities typically have to be shown on the plans as well has dead load reactions from each girder, which can be a pain to accurately calculate when you have a varying overhang in a curve. Everything has to be detailed to spec on a bridge (at least for the DOT in my state), even the typical details. None of these things are hard, just not fun to deal with.

 

[BRGENG]

Your first few bridges will involve heavy calculations unless you just trust your PC. After you can do the hand calc’s that match the PC then the calc’s are quick and easy. We design between 70 and 100 bridges a year, some DOT mainly County bridges. Typically lengths under 300 ft with spans up to 100 ft, most of your bridges fall in this range. The calc’s take a few days, a good CAD tech will take care of the roadway plans. Would you rather go to a site visit in the middle of town or down some County Road at a nice stream crossing? Worst issues can be HEC models, getting a bridge to fit the site that works with road standards, usually a problem in wide flood plains or within city limits. Right-of-way can be a blessing or a nightmare, you can meet great people that remind you of your grandfather or someone that hates the current county commissioner and will not talk to you. But give them some new fencing and a new field entrance and it is amazing how easy it can be. You have to be a people person, you will spend more time dealing with individuals then you will with calc’s.

If you think that once you design one you have designed them all rethink what you are doing. The new NU girders can span 150 feet, design a new product that can be fabricated locally to replace small spans instead of installing box culverts. Think outside the box, don’t design the easy solution design the best solution. Often they are not the same, educate your clients, and teach them to build bridges instead of hiring a contractor. Counties can build probably 3 bridges for every 2 that contractors build if not 2 for 1. Get into pedestrian bridges were you are allowed construction budgets to engineer art.

Hopefully you will have good contractors in your area, that is one of the biggest differences between buildings and bridges I have seen. Bridge contractors in our area are local, they seem to have a pride in their work that I seldom see in buildings. The relationship is more like a design build; after all we all know that we will be working together again.

If you work for the DOT you might get stuck in the Central office and do nothing but design, great for new guys. Then you can move to regional office and do inspections deal with county officials but you will never get to do all aspects unless you are with a consultant.

I still love buildings and keep doing them to keep up with the codes but I would pick bridges over buildings any day. And with that, I need to get back to a building design, the architect made some last minute changes and need the plans in the morning.