Award of Excellence: Special Projects Category
KBP Coil Coaters Structural Fire Repair
Submitted by Restruction Corporation
KBP Coil Coaters
San Diego, California
ChemCo Systems, Inc.
Redwood City, California
An extremely hot fire occurred inside a metal coating facility causing serious structural concrete roof structure damage. The building was constructed in the 1950s using a conventionally reinforced concrete folded roof plate slab, designed at 3-1/2-in. thick. The roof span was 85 ft between supports. Significant testing, both destructive and nondestructive was utilized to determine the extent and boundaries of the fire damage. The testing also helped determine the size and location of reinforcing bars. Structural analysis and modeling of the roof plate stresses was completed. The stress distribution models and unique original design eliminated several conceptualized repair schemes.
It was determined that partial depth hydro-demolition was required to insure the highest concrete bond strength and reestablish the concrete to reinforcing steel bond. A wet mix shotcrete was used as the repair material. Epoxy bonded composite materials were installed to assist the repaired roof section in flexure. Trial repairs and subsequent trial testing proved the repair scheme effectiveness. Code analysis of the structure determined that the 1950 code for shear was less stringent than the current code. This was evident as numerous shear cracks were found in the roof plate slab. Epoxy injection was completed to bond the shear cracks. Additional epoxy bonded composites were installed providing additional roof plate slab shear strength.
The Denver Building department required a 4-hour fire rating of the epoxy bonded composites. This stipulation was met. After review of the trial repairs, the building department issued a permit and large scale construction started. Approximately 7140 square ft of concrete repair, 60,000 square ft of epoxy bonded composite and 3150 lineal ft of crack injection was completed.