ReEngineering the Engineer: We’re Not in Kansas Anymore
When I left my old firm in the early 2000s, my breadth of experience was mostly in hospitals and medical facilities—new and renovations. Having all my eggs in one basket wasn’t how I wanted to run my company, so I was determined to diversify the types of work my firm had to offer. Through the years, we expanded our portfolio of project types to just about everything except residential.
Expanding into new building categories of work never seemed to bother me much. Structures are structures, to a certain extent, which I realize is a bit of a gross exaggeration. There are certainly nuances to each building category, but gravity design and lateral analysis for each category is about the same for all of them. I’m not suggesting the same holds true moving to different building heights; there’s a huge difference between low-rise and high-rise design, but that’s not my point.
Most of the structural systems we work with have their place in different types of building categories, but there’s some cross-pollination. So even if you’re working in one particular building category, you eventually get exposed to other structural systems. And generally, as your firm grows, you start getting exposed to systems that are new to you.
For quite some time, most of our work centered around our office: North Carolina and the immediately adjacent states. There’s a lot of comfort in that. You get a really good understanding of what’s expected for most building categories.
North Carolina is a wide state with mountains in the west and beaches to the east. As our work grew, so did the locations we worked. There are significant differences between design issues in each region. The mountains have high snow, perhaps some site-specific wind requirements, and the beaches have high winds, perhaps some storm-surge requirements.
Although these requirements are different from the issues in Charlotte, for example, the design requirements all can be found in the Code: IBC, ASCE 7 and sometimes local jurisdiction requirements. We know how to read the Code, so it’s relatively easy for us to learn how to deal with design requirements in a new area.
Two years ago, we were invited by a local architect to an RFP for a national client. The client was adding some prototypical small additions adjacent to their existing buildings. There were quite a few buildings in the RFP, and they were scattered all around the country. We aren’t registered in every state, so we elected to respond to ones where we already were registered. Many were in states where we had done very limited work.
We decided to design a prototype with some base criteria, then sort out high snow, high wind or high seismic, and make adjustments to those accordingly, keeping the general systems intact. It quickly became apparent there’s no resource to determine much about the local geotech conditions. The Code has some assumed values to use, but there are exclusions, and they’re very conservative. There’s enough variation in North Carolina that we knew we could be up against some real unknowns.
Ground Conditions Matter
Of all the unknowns associated with working outside your own backyard, this is probably the one thing that worries me the most: not being familiar with local soil conditions and the associated “gotchas.” Not only is it embarrassing to get caught with your pants down, but it could be a significant hit to your profitability if the foundation design is more complicated than you thought.
Fortunately, this client had records of all the buildings in its portfolio and even a couple soils reports. Although the structural general notes for those existing buildings didn’t include much information about the actual soil conditions per se, the details spoke volumes about the foundation issues.
In general, the sites were typical spread footings, but several projects were in the Dallas area and had expansive soils. We requested some new geotech studies and were able to get the detailing for those projects incorporated into our documents.
We all know the areas where we work really well. But when we travel to new areas, we need to be thinking about all the design information that may be different. Structural loading information is easy to find in the Code, but intangibles such as soils and foundation issues only come from experience and reading. Our trade magazines have articles about projects all across the country. Reading those often can provide clues to design issues at those locations and make us better prepared when we get there.
Douglas G. Fitzpatrick, P.E., is the founder, president and practicing engineer of Fitzpatrick Engineering Group, a 17-year-old structural engineering firm specializing in commercial and healthcare building design; email: [email protected].