Mike Vogel’s structural engineering team at Graef designed the Baird Center to be strong enough to carry the weight of a boat show, and stiff enough to avoid vibrations causing a “Jurassic Park” ripple effect in wine glasses if a crowd jumps in unison to a live band’s hit song.

Those are just some of the standards used to engineer the addition onto the downtown Milwaukee convention center. Some of the structural challenges are even more stringent than the demands on a typical arena, for example.

Vogel is a principal and senior structural engineer for Graef, the Milwaukee-based consultant that handled that work for the $456 million Baird Center expansion that is set for a mid-May grand opening.

“It’s really fun to be a part of helping solve society’s challenges, whether it is a large vertical construction project or designing a robot or machine to help us,” Vogel said.

Heavy loads

The addition is designed to feature big, open spaces for its two major convention halls, and Vogel’s team tested to make sure the structure could handle the weight of those events.

“This is long-span that has to take expo center loads, which are gigantic,” Vogel said. “You can imagine a boat show, or a hot tub show with a bunch of tubs filled with water.”

That means the floors of the convention hall are built to handle more weight than, for example, the roof of a typical sports arena. General building code standards require the roof of an arena to handle the weight of its own materials – called “dead weight” – but also up to about 30 pounds per square foot of snow buildup on top. The convention center’s exhibit spaces, by contrast, must handle up to 350 pounds per square foot in addition to their own dead weight, Vogel said.

“That gives them the maximum flexibility to attract events the community can appreciate,” he said.

Bad vibrations

It’s a whole different challenge to stop those stout floors from vibrating as people walk around or dance, or as bands play music with heavy bass.

That was another factor to consider, since the Baird Center’s second-floor ballroom is directly above its exhibition hall.

“You don’t want to excite that floor so that the lights below start moving,” he said.

Stopping that vibration is a separate challenge in addition to designing a structure to support weight without collapsing, Vogel said. Wisconsin Center District officials wanted the ability to have dinner and dancing in close proximity without glasses vibrating on tabletops, he said.

“Low bass starts to resonate with structure and can excite a structure so it can start to want to move harmonically,” Vogel said. “There’s different criteria if you have a concert and you have a bunch of people doing ‘Jump Around’ and all bouncing in unison. That will also excite a structure. That is very different than somebody walking on the floor.”

The depth of the structure contributes to its stiffness, and also more structural mass will dampen vibrations, for example.

Big numbers

Vogel ran through some of the stats on the materials that comprise the Baird Center’s structure.

It has 6,000 tons of structural steel, or about the equivalent to 12 fully loaded Boeing 747 airplanes. That includes more than 569,069 separate pieces of structural steel, held together by 169,152 structural bolts.

Think of those as the pieces of a Lego set or an Ikea table that haven’t been assembled. Graef designed the structure and created the instructions telling builders how to put them together. Bringing that work in house was among Vogel’s initiatives at Graef that can cut weeks off a project schedule. During the original convention center’s construction, paper design drawings were sent to an outside firm that drew up the assembly instructions.

Builders on the Baird Center expansion used those instructions to tell steel suppliers which parts to ship to the site and when they’d be needed.

“It comes out to about four truckloads, twice a week,” Vogel said. “They get four truckloads of steel. They erect that. They get another four truckloads. They continue until they are done.”