Colorado Real Estate Journal -

The Data Center’s Structure

Jeffrey DAndrea PE SE LEED AP Associate, Thornton Tomasetti, denver

---

Imagine a building with a level of durability beyond that of every other building within miles. Inside, servers might be routing 911 calls. The building may contain the communication channels needed after the big earthquake hits. Cool air is flowing beneath the access floor. All around is expensive, cutting-edge technology. Temperature and humidity are controlled within a decimal point. Imagine a building designed like a machine and built like a tank.

Purpose and function lead the design requirements, and the engineers behind the technology – the servers, the mechanical equipment and the electrical service – are the stars of the show.

But all of these functions are built on the structure, and there is no structure exactly like that of a data center.

Structural Loads. The normal safety factors built into codes like the International Building Code and ASCE 7 are a starting point.

They are a bare minimum. Often a data center owner will want a cost-benefit analysis of raising the level of earthquake or wind load. The design wind speed will frequently be increased due to seismic loads governing the lateral system requirements. In many cases, a small increase in cost can achieve a large increase in strength or redundancy.

Live loads in a data center are much higher than those found in a typical building. The lobby of an office building is usually designed for 100 psf. On a data hall, we start the bidding somewhere around 250 psf – a load level regularly used at loading docks! If you are thinking of converting an existing building into a data hall, think twice, and hire a creative structural engineer. Don’t forget to calculate your realistic clear heights and account for some new structural framing beneath the existing floor.

On the other hand, you can confidently carry the world on an 8-inch thick slab on grade.

Coordination. The more complicated the building, the more chance for conflicts and the greater need for coordination.

With the right design team, you can integrate and optimize these cutting-edge, interdependent systems. If your data center is more energy-efficient, serviceable and flexible than your competitor’s, you are playing with a deck stacked in your favor.

Your structural engineer is part of this team effort, too. He or she needs to anticipate depressed foundations, generator vibration, cooling tower dunnage, hanging load requirements, and heavy water main support. In the expansive soil areas of Colorado, the structural engineer had better understand what needs to be founded on bedrock, and what components might be allowed to heave with an expansive soil. It’s a balancing act based on knowledge and experience.

Structural Strategies

Speed to Construction. Once the green light is given to start construction, speed to market is a huge concern in today’s climate. If the team can get your data center up and running a month earlier, that month of profit can pay for a lot of “more expensive” decisions in the design and construction process.

Some structural engineering firms can provide a 3-D BIM (building information model) that, for example, a steel fabricator can mill order from.

This alone can save weeks in the schedule by eliminating steps like quantity takeoffs done by the steel fabricator. This process also reduces risk by serving as a baseline. Your subcontractor A is bidding on the same quantities as your subcontractor B. A BIM also offers certainty: if it’s in the model delivered to the fabricator, it will be on the truck delivering the steel.

Flexibility. Future flexibility hinges on the choice of structural system. Post-tensioned concrete structures are not a good idea if you know you will need to core holes in various places during the operational life of the data center.

Hitting an un-grouted PT tendon with your core drill sounds like a shotgun, and that tendon is going to fly out of the face of the slab like a rubber band. We find that steel framing is frequently a better choice, for both for last-minute revisions and future wholesale changes. It is easily exposed and additions can be welded.

A flexible structural system allows for bidding and purchasing to proceed with early structural packages while final coordination is being completed.

The right structural engineer can achieve a structure that is nearly invisible in the finished product. Data halls can be made column-free, allowing ultimate flexibility in program. Lateral force resisting systems, like braced frames or shear walls, can usually be located at perimeter bays, reducing the coordination and increasing the usefulness of the interior space.

Practicality. Often a data center is designed for final fitout, but not completely built for day one. By day two, new, more efficient mechanical units may be available, with a different weight and footprint. The structural engineer has to anticipate these kinds of changes and efficiently build capacity into the original design.

A data center better be watertight! Limiting deflections of spandrel beams and using a concrete slab on the roof provides an enclosure that is serviceable, durable, and offers redundancy for leaks.

Building Information Modeling. Your structural engineer should be using a 3-D BIM for drawing production.

If not, the engineer is lagging the industry. This is an essential tool for the coordination of all disciplines – during design, fabrication, construction, and for the life of the building.

Owners now have the ability to own these BIMs and use them as working documents, updating and coordinating all systems throughout the building lifespan.

Conclusion

A data center’s structure should not be an afterthought. It is the backbone upon which everything else is built. Remember that the optimal coordination of expensive, interdependent systems, along with future flexibility, is probably more important to the bottom line than saving a few bucks in the short term. With thoughtful design of these complicated, robust buildings, your structural engineer can help create a better data center.