Engineers like to work from the top down, designing the roof, then the decks, the structural supports, and finally the foundations upon which the entire structure rests. Unfortunately, meeting construction schedules often hinges on purchasing certain components early in the process, before the overall design has been created. And the first activity onsite is preliminary foundation work, again for a structural design that has yet to be finalized.
Such was the case on a three-story structure now nearing completion in Frederick, Md., one of the largest office tilt-up buildings constructed to date. Its 310,000 square feet of space is the new home to Wells Fargo Home Mortgage, which previously occupied office space in a number of different buildings throughout the area.
Thanks to years of experience working on tilt-up projects together, the team of Frederick, Md.-based general contractor Morgan-Keller Inc., and designers at LJB Inc., Dayton, Ohio, was able to offer a plan that would meet the developer's tight schedule while providing a top-notch appearance.
LJB's confidence came from knowing it could rely on Morgan-Keller, which has 17 years of tilt-up experience as a member of LJB's Con/Steel Alliance, to properly execute the design.
Using a concurrent design approach, LJB provided foundation drawings just two weeks after being awarded the project, which enabled a prompt start on site work. Steel drawings were nearly finalized approximately five weeks later, enabling the contractor to place a mill order for the steel. Structural steel fabrication drawings were completed just 14 weeks from the award date. Concrete construction began in late April 2006. Less than 90 days later the foundations, floor slab, and exterior walls were in place.
Although clearly proud of his team's accomplishments, LJB's senior structural engineer Jeff Griffin, Ph.D., P.E., acknowledges, “Phased and sequenced construction are becoming the norm in the tilt-up industry.”
Phasing and sequencing
When Wells Fargo put out the request for proposals for a new office facility in the Frederick, Md.-area, one of the key criteria was being able to begin moving in by March 2007. “Tilt-up was the only way to get it done,” says Bryan Shockey, senior project manager for contractor Morgan-Keller. And there was another main ingredient. “We had to get everybody onboard quickly to make it happen.” Morgan-Keller previously has worked with the developer, Frederick-based Matan Companies, which contributed to the project's rapid progress.
Sequencing played a key role in constructing the project as quickly as possible. Construction began with the center structure, per Wells Fargo's request, while designs were still being completed for the rest of the project.
After the foundation and slab were placed, the panels were manufactured and lifted into place. Next the second level steel framing was installed in one-third of the building, working around the braces. The third level followed, with steel and the roof framing. The middle and last third of the building were framed up in the same sequence. Then the third floor slab was placed. When it reached 2500 psi and the roof deck had been completely fastened, the braces were pulled and the second level slab was placed. Meanwhile, the same process had been started on the second building.
- Project: Wells Fargo Home Mortgage
- Location: Frederick, Md.
- Engineer: LJB Inc., Dayton, Ohio
- Contractor: Morgan-Keller Inc., Frederick, Md
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