DESMAN project receives Quality Concrete Award
December 2007
DESMAN is pleased to announce that the Washington University Central Underground Garage has received one of Concrete Council's 2007 Quality Concrete Awards.
Congratulations to the DESMAN Team of Mahinder, Yury, Steve and Jonathan; Mackey Mitchell and all other companies who worked hard on this project! Project details specific to this award are listed below.
1) Project Description:
The Central Underground Garage is a three-story cast-in-place concrete parking structure that serves as the foundation for Washington University's new University center, which currently is under construction. The parking garage extends 35 feet below the grade elevation and accommodates 523 parking stalls. Each level is approximately 70,000 square feet. A 15-inch-think concrete lid separates the garage from the University Center. The lid slab also included transfer beans as large as 4 feet by 8 feet. Three elevator shafts that will be part of the University Center as well were incorporated into the garage. It also houses many of the utilities and equipment required for the University Center.
2) Procedures Employed:
Since the complete parking garage is underground, the team first had to put in an earth- retention system, dig a hole three stories down and then clad the retention system with a structural concrete wall. Concrete Strategies utilized a 37-foot-tall, one-sided forming system by EFCO. The team had to pour the perimeter walls in a one-lift pour, 40 feet high. Once the perimeter was in place, Concrete Strategies was able to start the parking garage from the lower level and work its way out of the hole.
3)Special, Unique or Challenging Situation:
Challenges included limited sight restrictions and access to the hole, especially when the team had to remove the ramp for the first level of garage pours. Strategies had to perform a lot of preplanning and scheduling to make the pour work. There were numerous deliveries into the hole with a tower crane. There was only one crane on the project, so the team had to have a very detailed schedule to make the best use of the crane.
The project involved 37-foot-tall, one-sided formed walls. Concrete Strategies welded pivot brackets for the ties onto the actual retention system in order to form the walls. With the thickness, amount of concrete and super-strong system, it was a very difficult wall to pour. Concrete Strategies had to hit within 1/2 inch on the tie walls to match up the forms. When the form was flown over, all the holes had to match up.
As mentioned above, the top floor of the garage is a structural member that carries the load of the University Center. Transfer beams were used to support columns from the building above as well as 3 feet of earth fill in some areas.
4) Materials Used:
Their project included 5,000-7,000-PSI concrete for the columns, 5,000-PSI concrete for the decks and 6,500-PSI concrete for the perimeter walls. The dimensions for the transfer beams were as large as 4 feet wide and 8 feet deep.
5) Special Quality Components of the Project:
The architectural finish on the forms was paint-grade quality. The team took extra time and effort to make sure the quality of concrete was acceptable to receive paint. This level of work is unusual for a garage. Most garages are not painted and so quality level is not as high for finishes.
The cast-in-place concrete required a stone form liner. The concrete was poured at a .38 water-to-cement ratio for longevity of the garage. Regarding sustainability, there were no requirements, but Concrete Strategies did use fly ash in its concrete mixes, and all aggregates were purchased from local suppliers.
6) How this project has encouraged the use of more concrete:
Everything in the garage is concrete, including the slab on grade. This use of concrete was a departure from Washington University’s typical practice of using asphalt. However, for this particular project, Washington University agreed to use concrete and also an under-draining system to increase longevity.
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