Proj Overview

Project Overview

Administrators at Fort Drum (aka Wheeler-Sack Army Air Field) decided to construct three-story barracks to handle the growing number of soldiers at the base.

At three stories tall, the buildings needed to meet Army force-protection requirements that prevented progressive collapse in case of an exterior wall being compromised.

Precast Solution

Four barracks were constructed with precast concrete hollowcore plank as the flooring system. The plank uses a cantilevered design that does not rely on the outer wall for support.

The first bay was designed as a 10’ 8” backspan with a 10-foot-long cantilever rather than as a 20’ 8” simple span. In the event of a blast in which the end wall (which normally supports the slabs) is destroyed, the precast slabs cantilever 10 feet from the interior bearing wall and remain supported by an interior wall.

The 8-inch-thick slabs will have a 10-foot overhang with almost 3 inches of deflection, which can later be re-supported.


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Project Team

Architect, Engineer of Record, and General Contractor

Clark Construction Group 


United States Army 

Precaster and Precast Specialty Engineer

Oldcastle Building Systems 

Key Project Attributes

  • Fabricating the precast concrete components under controlled conditions in the plant ensured high quality and tight tolerances, minimizing field adjustments and speeding up erection time.
  • Casting components off-site while site work was completed allowed precast concrete pieces to be ready for erection as soon as foundations were ready, speeding up construction.
  • Hollowcore plank provides long, durable spans that offer design flexibility and low maintenance.
  • Design application provides force protection to ensure stability even after a blast may compromise exterior walls.

Project/Precast Scope

  • Four 81,000-square-foot buildings with precast concrete hollowcore floors to provide blast protection that prevents progressive collapse.
  • Design features exterior wall supporting hollowcore with a 10’8” backspan with a 10-foot-long cantilever, rather than one 20’8” span. This ensures that if the exterior wall is compromised, the hollowcore remains supported by the cantilever of the interior wall.
  • 8-inch-thick slabs feature four ½-inch top strands in addition to standard six ½-inch bottom strands.