How Long Did It Take To Build That?

Over the weekend, we took my son and my 16-year-old (almost 17 years old, now) to visit the Hall of Justice.

All right, all right, I’m kidding.  Slightly. That building up there (which really was the inspiration for the Hall of Justice) is the Cincinnati Museum Center. It’s not quite as impressive as usual, because there’s a whole lot of internal and external renovations going on, but it’s still pretty cool.

“How long did it take to build that?” my niece asked.

“Two years!” my son declared.

“I don’t know,” I confess.

“Maybe forty years,” my niece suggests.

How long did it take?

Well, according to the Museum Center web site, construction started in August 1929 and was completed on March 31, 1933. So, about 3 and 1/2 years.

Well. That was short.

The construction time? Or the article?

Both.

Yeah, well, the building was built in the 20th century. As I pointed out to my niece when she guessed – half tongue-in-cheek – that it took 40 years, the building was originally designed to be a rail hub. They had ways to haul supplies and materials in, and things like cranes and bulldozers and the like. It wasn’t all teams of oxen dragging granite blocks and the like.

Rail hub?

The building that is now the Cincinnati Museum Center started out as Cincinnati Union Terminal. See, as Ohio History Central explains, Cincinnati was linked to “a number of other major cities through its rail lines, but the original system had not been well-coordinated. Trains ran through several different railroad stations around the city. In the early 1900s, railroad companies began developing plans for a single railroad terminal that would provide service for all passenger and freight lines entering the city. It was not until the late 1920s that construction actually began on the project, which became known as Union Terminal.”

The Union Terminal complex, at its height, took up 287 square miles acres and had 94 miles of track – some of which you can still see if you visit today. It was designed to handle a lot of traffic. See the way that the building rises up in a hemisphere in the center? That facade covers a half-dome that, when it was built, was the largest half-dome in the world (and is still the largest in the western hemisphere). The terminal could handle 108 arriving and 108 departing trains a day, and was designed to accommodate as many as 17,000 people (although it hit over 20,000 during World War II, when soldiers passed through on the way to their posts).

Union Terminal operated from 1931 to 1972, when it finally closed for business. The city of Cincinnati purchased the site in 1974. In 1979, the Joseph Skilken Organization converted it into a mall, which opened with 40 tenants on August 4, 1980. The mall failed and closed officially in 1984, although a single store (Loehmann’s) continued in operation there until 1985 and a weekend flea market operated on the site for several years.

In 1986, a Hamilton County bond levy was passed to fund renovation of the site and to convert it into a museum. Four years later, in November 1990, the terminal reopened as the Cincinnati Musuem Center. The next year, it also began serving as Union Terminal once more. Amtrak began thrice-weekly passenger train runs on July 29, 1991.

So, how long did it take?

It depends, ultimately, on what you’re looking at. It took three and a half years to build the original Union Terminal facility. Turning it into a mall took 23 months, and turning it into the Cincinnati Museum Center took four and a half years.

Why’s it called a “Bobcat”?

Our HOA is tearing up and repairing the parking lots in my complex this week, forcing me to park at a distance from my condo. Yesterday, after getting home from kindergarten, my son saw this parked in front of our building:


“What’s that?” he asks, excited.

“It’s a bobcat,” I answer.

“That’s silly,” he tells me. Then he thinks for a moment.  “Why’s it called a bobcat?”

“It…” I begin, and then I stop. “You know what?”

“What?” he asks.

“I don’t know why.”

Why is it called a “Bobcat”?

This turns out to have an extremely simple answer.  The machine is one of a number of vehicles manufactured by the Bobcat Company,  Bobcat started in North Dakota in 1947 and still has their headquarters and three production facilities in that state.  Other production facilities are found in France, the Czech Republic, and China.  They were acquired by Doosan Infracore, a South Korean conglomerate, in 2007.  The machines are called “Bobcats” for the same reason that trucks built by Chevrolet are called “Chevys”.

What is that particular machine in the picture?

The machine in the foreground is a Bobcat S650 Skid-Steer Loader, while the one in back (mostly obscured by the S650) is a Bobcat S250 Skid-Steer Loader – a discontinued Bobcat model.  Here’s a better picture of one:

1819564_1

…Skid-Steer Loader?

Yeah.  Here’s how Wikipedia explains the process that gives them their name:

Skid-steer loaders are typically four-wheel vehicles with the wheels mechanically locked in synchronization on each side, and the left-side drive wheels can be driven independently of the right-side drive wheels. The wheels typically have no separate steering mechanism and hold a fixed straight alignment on the body of the machine. By operating the left and right wheel pairs at different speeds, the machine turns by skidding, or dragging its fixed-orientation wheels across the ground. The extremely rigid frame and strong wheel bearings prevent the torsional forces caused by this dragging motion from damaging the machine.

In other words, they turn like tanks.  And the skid-steer process allows them to turn without moving forward, because the left wheel pair can go forward and the right wheel pair can go backwards (or vice versa), making them able to work in cramped conditions.

How Do You Build a Bridge?

It’s Saturday, and my wife and my son and I are standing on a deck overlooking the Ohio River. My son is fascinated by the barges working up and down the river, and he’s running back and forth pressing his face up against the rail and staring. Then he looks up at the Daniel Carter Beard Bridge, known locally as the “Big Mac Bridge”, and just stares. He’s seen the bridge before, but never this close from below.

“Daddy? How did they build that?”

I’ve got nothing, really. So, I turn to Google and start researching. Here’s my disclaimer: I was originally, before I started researching, planning on making this all about the different types of bridges and how they get built. And then I started finding out about all the different types of bridges, and realized that I’d have to write a whole book to do it successfully. And that seems a touch… extreme. So we’ll just focus on this specific type of bridge.

According to Wikipedia, the bridge is a “twin span steel tied arch bridge”, which is a type of bridge with one or more arches braced at either end into a foundation, with the bridge itself passing beneath the arch. Cables or other supports then connect the bridge to the arch along the length of the arch – something you can see by looking at the pictures of the bridge. SteelConstruction.info () states that:

Thrust arches rely on horizontal restraint from the foundations…. The vertical and horizontal reactions resolve into a force along the arch members – the horizontal component is of significant magnitude.

The tied-arch offers a solution when it can be arranged that the deck is at such a level that it can carry the horizontal force as a tie member….

By taking the arch thrust through the tie member, the primary requirement for the substructure reduces to only carrying vertical loads. It can be seen that one end will still require a longitudinal restraint to carry wind, braking, acceleration and skidding forces, and that the other end is permitted to move longitudinally.

Now, I’m clearly not a mechanical engineer. But, reading the rest of the article, I believe this means that the arch does all the work of supporting the weight. Since arches get stronger as they compress, the load on the bridge (the “deck” described in the quote above” actually helps strengthen the bridge as a whole. As long as the deck itself can support the stresses, obviously.

So, how do you build one of these things? Luckily, the American Institute of Steel Construction has the text of Design of Steel Tied Arch Bridges: An Alternative online, which describes the process generally. It states:

In the proposed scheme, the arch ribs are erected first. They may be erected using a high-line or each half of the arch rib may be rotated into place from it bearing. During the erection, thrust must be taken by the abutments or by a temporary cable between the ends of the ribs.

After the arch ribs are erected, permanent cables are placed between the ems of arch ribs to carry dead load thrust. The cables must be supported by the hangers to prevent sagging and reduction of the effective modulus.

The deck and tie beam are precast concrete units. Each unit of the deck exerts full width of the bridge. ‘The deck is cast integrally with the tie beams. Each unit is equal in length to the hanger spacing. The deck is supported on composite steel transverse floor beams which frame into the tie beams. The units are floated under the bridge and lifted into place by hoists connected to the arch ribs.

When the units are in place and cast-in-place concrete completes the closure in the center, the units are post tensioned. Finally, the ends of the deck are cast-in-place and the deck is post tensioned to the ends of the arch ribs.

Sadly, I couldn’t find any specifics about how the Big Mac Bridge was built. But, since it’s a tied arch bridge, it should have been something along these lines. I’m not done, though, because my son also wanted to know how the legs (or piers as they are apparently properly known) got put in the water. For the answer to that, I’ll turn to an article on Quora with the useful title How are bridges built over water?  Apparently, there are three methods:

a) foundation may be sunk inside the bed from the top
b) Rigs may be employed to cast / drive piles on which a cap is then cast to support the pier
c) A cofferdam (a wall enclosing an area inside a water body) is first prepared, inside which water is constantly pumped out and dry working conditions are maintained. The foundation is then constructed inside the cofferdam.

Again, I wasn’t able to locate any specifics on how the Big Mac Bridge was built, so I don’t know which method was used.

Oh, and here’s a lovely fact. The bridge opened in 1976, with southbound traffic being able to use it in January of 1976 and northbound traffic being able to use it in December of the same year. Two years later, the Federal Highway Administration released a Technical Advisory designed to “acquaint the Federal Highway Administration and States with problems recently associated with tied arch bridges and to emphasize the need for a thorough evaluation of alternate designs which provide more redundancy”. It hen goes on to provide five bullet points on the way these bridges can fail, and why some other bridge type should be used. What a lovely thing to know about a bridge that I probably drive on eight times a month.