Precast Concrete Prototypes



PINELLAS COUNTY, FLA. - The Pinellas County School District developed a prototype that used precast concrete to construct four school additions in the summer of 2021. “We developed a kit of parts that could be used in different configurations,” describes Ted Williamson, President of Williamson Design Associates.

The prototype can be scaled up or down from 6 to 12 additional classrooms with an option for one- or two-story construction. “We could go bigger by just adding modules, so the design is very flexible to add space as needed. In the end, the precast prototype turned out to be an economical and fairly simple system,” Williamson says.

The objective of the Pinellas County School District was to enlarge the existing schools at their current location without disrupting students and faculty. Because precast concrete components were cast off-site, fewer trades were needed on the active school campus. It required no laydown or storage area and was quickly enclosed for other trades to complete interior work.

Long Weekend

Three of the four schools (North Shore Elementary, Sanderlin Elementary, and Sawgrass Lake Elementary) were constructed sequentially during the summer with only an eight-day typical duration to erect the two-story classroom additions. As if eight days were not fast enough, the Shore Acres Elementary project had to move even faster. Due to site constraints, it had to be completed in just one weekend. The building was up when students returned to school on Monday morning. Jordan Wise, senior project manager with Ajax Building Company, described the carefully orchestrated sequence of events over that January weekend at Shore Acres Elementary.

The accelerated building construction got started with the arrival of the crane on Friday afternoon. Coreslab Structures had the precast concrete panels at a staging area, ready to go. The team worked late, installing panels under the lights. Work continued on Saturday, when they finished erecting, welding, and grouting the precast concrete wall panels. On Sunday, the hollow-core slab was installed and in just three working days the shell was completed. All this was necessary because the administration building, portables, and recreation area were all within the direct path of the crane, its swing radius, and the staging area. Access was through a student drop-off area—all factors that mandated that work be performed only when school was not in session

Bundled Up

Prototypes are nothing new in Florida and are used frequently to address the shifting and growing population. Once a school district agrees on a prototype, it is used over and over again and then reviewed and refreshed as the building code changes every three years.

“I thought the prototype concept was a great way to build three schools in a short amount of time,” says Mark McKeny, director of business development with Dura-Stress Inc. On their
own, these small building additions might not have been cost-effective as a precast concrete system. McKeny says that bundling the school projects made more sense for the economies gained from engineering and shop drawing phases through production and installation.

The selection of precast concrete was facilitated by the willingness of the design team and Pinellas County Schools to collaborate with the precasters. “They were open to hearing input from us regarding efficiencies and constructibility,” recalls McKeny. Dura-Stress worked with Skanska to optimize logistics within the very tight sites. “We kept the piece sizes on the smaller side, so that a large crane was not necessary,” he says.

Thin Brick

Pinellas County still uses traditional methods including brick, block, tilt-up, and other materials for school construction. With the current volatility in the construction markets, precast concrete systems were added to their arsenal. “With the fluctuations in steel prices and the potential for long lead times, using a local precaster made the most sense at this time. We always evaluate market conditions for any construction project,” says Williamson. Time was of the essence and the budget just as critical. To be as economical as possible, most of the school annexes featured smooth form finishes.

The precast concrete wall panels were then painted in the field with a textured paint. “The prototype allowed for flexibility that could take advantage of not just the economic simplicity of precast but its inherent versatility, if required,” McKeny says. The exception was seen at North Shore Elementary school, where thin brick was inlaid at the precast concrete plant to match the rest of the campus in the historic neighborhood. “We were moving so fast that we had to utilize thin brick that was in stock from our supplier—that way we didn’t have to wait for a possible back order of a custom color,” recalls McKeny.

With the prevalence of severe weather along the west central coast of Florida, it is not ideal to have students in portable classrooms. The hardened walls of precast concrete provide shelter from high winds and large projectiles, despite not being designed to Federal Emergency Management Agency standards. After construction of the precast concrete prototypes, the portables were removed from their temporary location.

“The biggest benefit of using precast was that it saved time and labor costs on-site. The cost was equal or comparable, but the savings were realized in the reduced construction schedule,” Williamson concludes. The repetition of the prototype design also simplified the classroom fit out. The result is a simple kit of parts that could be manufactured off-site, assembled quickly, and finished in time for the first day of school. The precast concrete walls provide flexibility to scale up or down for different campuses.

Pinellas County plans to build more precast concrete schools and Ajax Building Company has four more prototype projects in the pipeline with the county. “On this site [Shore Acres Elementary] because of the limited area and the numerous site constraints, the precast solution did work well,” Wise concludes.

Source: ISC Page Pro Digital Publication