This summer the San Diego State University students who signed on to help Colin Milberg collect data for his construction tolerance project learned something they wouldn't get through even the best classroom simulation. Gathering as-built data on several concrete projects in the San Diego area, they learned the realities of jobsite logistics, up close and personal: You don't have an unlimited amount of time to admire and evaluate the newly stripped concrete at your leisure. Rather, you have to move in, grab what information you can, while you can, and then get out of everybody else's way!

One major goal of Milberg's project, which was described in ""how close are we getting?"" (July 2007) and "two field reports"" (August 2007) is to determine the industry's current “process capabilities.” In other words, how close to the plans are we building—or can we actually build—concrete structures? To come up with those process capabilities, he first has to gather a lot of data, which is where a high-technology 3-D scanner is being put to good use.

Tuan Nguyen and Quinn Booker set up the laser scanner to gather as-built data from a construction site in San Diego. Scanning approximately 1200 square feet over 288 surfaces on seven vertical elements in this relatively clear area will require two to three setups because of the post shores. The data collection will take eight hours.
Colin Milberg Tuan Nguyen and Quinn Booker set up the laser scanner to gather as-built data from a construction site in San Diego. Scanning approximately 1200 square feet over 288 surfaces on seven vertical elements in this relatively clear area will require two to three setups because of the post shores. The data collection will take eight hours.

“We're finding that even though the scanner is fast, time is still the big issue,” says Milberg. Unlike taking a snapshot photo, scanning isn't instantaneous; even at lower resolutions, it takes time. Meanwhile, there are lots of people trying to move the construction forward, and they move onto each floor sometimes only one day after the formwork is removed and post shores are installed. So where once there was a clear view of all the concrete elements, suddenly there are walls, piping and ductwork. And there are those post shores to contend with as well.

That means rather than doing one big scan of an area, the survey crew ends up having to also set up in another location—or several more locations—to be able to see everything. The result is that data collection is taking significantly more time than originally expected.

“At first we spent extra time and effort planning our strategy to cover the maximum area from each setup,” Milberg says. “The alternative, we figured, was to allow for a few extra setups and a little more overlapping coverage.”

With their first attempt at data collection in the field, Milberg and his students learned that even when the survey crew gets in at the earliest possible opportunity, there just isn't enough time to collect a complete set of measurements before things start getting in the way. That realization has led to the development of a new game plan.

“Now we're just coming up with a good rough plan and a starting location. Once we get onto the site and see what we are up against, we set up and start the first scan. While that's being done, we plan our other station locations.”

Milberg's team has collected data from two floors on one project and one floor on another. For each of those, the data from the various setups has been combined, but the analysis has yet to be undertaken.

He also has put together the initial forms for data collection, which are posted on the ACI 117 committee Web page. At this point, they are being used only by other members of the committee. Public access through a Web portal, which will include solicitation of additional data, is expected for later this year.

The next big surge in activity should come at the 117 committee meeting, set for 8 a.m. Tuesday, Oct. 16, at the ACI convention in San Juan, Puerto Rico.

Meanwhile, the San Diego State University students have gone back to study in their traditional college classrooms, but not without a better understanding of the realities of construction. And the quest for data continues.