Reinforced concrete - filled steel columns.
The Lester B. Pearson airport in Toronto is Canada’s largest and the world’s fourth busiest international airport. In 2000, the Greater Toronto Airports Authority undertook a major redevelopment of its facilities. A significant aspect of this redevelopment was the construction of a new passenger terminal facility to replace existing Terminals 1 and 2. One of the main architectural features of this new facility was the departures hall roof structure.
Pump nipple at base of column
Due to schedule and program availability constraints, the best construction method was a ‘top-down’ approach. In this approach, the departures hall roof structure was built ahead of the floor structure. The structural design of the departures hall roof required 43 pairs of 31-meter high reinforced concrete-filled steel columns (700 mm in diameter). These columns were erected full height (approximately 31 meters), and the upper 24 meters remained architecturally exposed in the completed building. As the columns were part of the architectural design, the exposed concrete needed to be unblemished, requiring innovation in column grouting technology. A single lift, on site grouting operation was chosen as it had minimal aesthetic impact on the exposed columns. This was the lowest cost option and was well suited to the top-down construction approach.
The chosen construction method required the concrete to be pumped in at the base of the column, using a single grout port. The full height would be filled in one continuous operation. "Bottom up" pumping of the concrete requires a highly fluid, fast flowing mix that can rapidly move up the pipe column. Pumping pressures had to exceed the gravitational force on the concrete and overcome internal friction due to flow restraint from the rebar cage and other inserts in the pipe section.
Due to the extreme height of the proposed grouting operation, a number of technical concerns needed to be addressed. A co-operative effort by the GTAA and the construction team was undertaken to develop and verify the necessary grouting procedures. The concrete mix was proportioned specifically for this process, and verified by trial batches. One column was erected and grouted on site in order to prove the grouting techniques and the resulting concrete quality. The grouting verification program proved successful in confirming the viability of the proposed single-lift grouting method.
The structural grouting requirements were successfully achieved without any aesthetic impacts to the prominent architecturally exposed columns and the entire grouting operation took only 15 minutes per column. Structural steel fabrication and erection proceeded independent of the grouting process, resulting in both cost and schedule benefits to the project.
Departures hall - level 3.
|Owner||Greater Toronto Airports Authority|
|Architect||Airport Architects Canada|
|Engineer||Yolles Partnership Inc.|
|Contractor||PCC/BFC Joint Venture|
|Material Suppliers||Dufferin Custom Concrete Group, Canron Corporation|