West Houston’s KATY Freeway

[I’ve been mean­ing to do a lot more of this, but bet­ter late than nev­er. This is one of the posts on a project I’ve was involved with at my for­mer employ­er. How­ev­er, for what it’s worth, this is the first struc­ture I’ve designed that has yet to be built.]

Over two years ago, I began work­ing on part of the design team for the IH-10 and Belt­way 8 inter­change West of Hous­ton, Texas. I spent about three months down in Tam­pa and then anoth­er 4 months on and off back here in Rich­mond work­ing on the job.

KATY Freeway Tall Piers

A view of some of the tall piers at the IH-10/BW‑8 Inter­change. Note the Texas star detail cast into each pier.

My role was as struc­tur­al engi­neer for the left-turn fly-overs. Those are the high­est por­tion of the over­all inter­change (.pdf file); the ones where you exit one free­way to the right to “fly over” the rest of the inter­change to head left onto the inter­sect­ing free­way. I did the struc­tur­al design for approx­i­mate­ly 1.2 miles of bridge, with spans up to 375 feet. All the bridges were sin­gle lane. Also, the struc­ture type was a dou­ble steel tub-gird­er. These are some very clean-lined struc­tures once fin­ished. I can say that, as I had no deci­sion in the struc­ture type and lay­out what­so­ev­er. I sim­ply decid­ed how thick to make all the plates. Sounds so sim­ple, does­n’t it?

The KATY Cor­ri­dor project is a huge con­struc­tion project, widen­ing and ren­o­vat­ing rough­ly 20 miles of IH-10 between Hous­ton and Katy, TX at a cost of $1.44 bil­lion (yes, that’s a B). The sec­tion this inter­change is in, called Con­tract D, came in with a $250 mil­lion price tag. That’s a rather large civ­il project, by any terms.

This was a great project to learn on, as curved bridges have some force effects due to grav­i­ty that many oth­er bridges don’t expe­ri­ence. The por­tion of the bridge that sweeps out beyond the straight line con­nect­ing the sup­port­ing piers cre­ates an immense twist through­out the bridges length (think of wring­ing out a dish­tow­el). This is resolved with­in the super­struc­ture by that tub (or trape­zoidal) shaped box sec­tion. The lev­el of force is tremen­dous, as is the size of steel plates involved in the bridge gird­ers. Two steel box­es which are 8′-6″ deep and 8′-0″ wide (at the top) car­ry a con­crete road deck and vehic­u­lar traf­fic up to 375 feet between piers at 85 feet in the air. There are three lev­els of traf­fic below the bridge at it’s high­est point. It is a sym­pho­ny of steel and con­crete that takes years to design and build.

My part in it was rather small, but I learned so much from it. I had the plea­sure of work­ing with great engi­neers who tru­ly want­ed a safe and aes­thet­i­cal­ly pleas­ing bridge. I real­ize there was, and remains, a great deal of con­tro­ver­sy involv­ing this project. How­ev­er, in the end, I hope the cit­i­zens of Texas can enjoy and appre­ci­ate their road. Struc­tures such as this one are a prod­uct of a soci­ety that cher­ish­es the auto­mo­bile almost as fam­i­ly. It’s nice when we can have pleas­ant roads and bridges with which to put them on.

By Jason Coleman

Structural engineer and technical content manager Bentley Systems by day. Geeky father and husband all the rest of time.


  1. [lives in hous­ton off of 290/west] WHY is it that HOUSTON has decid­ed to work on EVERY major hwy 10, 610, 59, belt­way 8 and what­ev­er else all at the SAME time…i can’t wait till the katy free­way is fin­ished and 59 isn’t closed any­more on the weekends…ugh…terrible con­stru­tion, and ter­ri­ble plan­ning IMO

  2. Well, Latisha, I guest you should real­ly direct your com­plaint to Austin, since this is a TxDOT project. Of course, my under­stand­ing is that the Texas leg­is­la­ture does a lot of real­ly odd things. As to the “why” part of your ques­tion, I’m afraid I was way too far the food chain of this project to begin to answer it. I can say this, if a state has the mon­ey to spend on con­struc­tion projects, they seem to rarely wait for a bet­ter time and just spend it immediately.

    Here in Rich­mond, there is a rather large bridge widen­ing project under­way about a mile from my home (also one of my for­mer employ­er’s projects). I under­stand how frus­trat­ing it is to have to deal with large civ­il project such as the KATY cor­ri­dor. They stretch for many years and cause incon­ve­nience on near­ly just as large a scale. How­ev­er, once it’s all said and done, traf­fic should be much bet­ter (at least for the next 20 years or so). Of course, hav­ing sev­er­al major arter­ies in the west­ern part of Hous­ton seems to be poor plan­ning, indeed.

    Well, that’s a lot of words for not much of a response. Thanks for post­ing a com­ment all the same. I hope to hear from you again sometime.

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