A single-level, double tee Condominium parking garage located in Denver, CO partially collapsed during the winter of 2014. Five double tee stems fell, crushing and trapping several cars below. No injuries were sustained during the event. Emergency shoring was installed shortly after the incident.
The atypical construction of the garage included precast double tee stems supported on conventional steel beams and columns. The steel columns extended below the slab a couple of feet on grade concrete and were supported by concrete piers.
A combination of factors led to the collapse of the garage:
- A high water table caused corrosion of the steel column supports. Damage extended into non-collapsed areas.
- There was no lateral bracing in the garage to prevent rolling of the steel beams.
One of the double tee stems was damaged beyond repair. The other four stems were found to be salvageable with minor concrete repairs. The original construction plan called for jacking of the salvageable double tees to the proper elevation and repairing the steel supports below. Restruction Corporation value- engineered the complete removal of the salvageable double tee stems and stored them offsite for reinstallation, following completion of repairs to the steel structure. The shorter tee stems were shored and jacked in place, as they did not collapse.
The repairs to the steel support structure consisted of installing all new concrete pier caps, hot-dipped galvanized steel columns, W-beam steel supports, and lateral support bracing.
The four salvaged double tee stems and one new double tee stem were then reinstalled. New hot-applied waterproofing was used on the top of the stems and additional bi-level drains were installed. Finally, a new concrete topping slab returned the garage to its original pre-collapse state.