SOLUTION

WJE's investigation consisted of two phases. During Phase 1, the structure was visually inspected, and core samples were removed from the walls, soffit, beams, and columns in areas exhibiting a range of conditions. In Phase 2, the structural elements were subjected to impact-echo (IE) testing to detect delaminations and locate internal cracks. Inspection core holes were used to calibrate and verify impact-echo results.

The investigation determined that the walls and soffit of the underpass exhibited significant visible damage from the fire, consisting of spalling up to 4 inches deep. The two columns within the underpass also suffered a significant amount of visible spalling, exposing reinforcing steel at a few areas. IE testing and observations at core holes identified possible delaminations and heat damage. The upper deck had only minor fire damage with small areas of shallow spalling and material damage. However, compressive strength results indicated that the undamaged concrete appeared to significantly exceed the original design strength requirement.

For the areas of damaged concrete, WJE provided general repair recommendations, including removal of damaged concrete by water-blasting or chipping and replacement with a cementitious structural-repair mortar, concrete, or shotcrete, as appropriate.