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.

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.