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Case Study

Centre 70 Parking Garage, Calgary, AB

Artis REIT is an unincorporated closed-end real estate investment trust primarily focused on creating value for unitholders through the investment in and ownership of quality commercial properties in select markets. Artis REIT’s portfolio is comprised of industrial, retail, and office properties in Canada and the United States.

Project Details

Services
SoundPrint® Acoustic Monitoring – Parking Garages

Monitoring system commissioned in February 1994

System has been maintained and upgraded as needed, operating continuously since commissioning

Structure Type
Two-way unbonded post-tensioned concrete ground level slab above parking garage
Monitored Area
5,967 m2
Number of Zones
3
Number of Sensors
60

Project Highlights

System has performed in excess of 97% of efficiency over its lifespan

Detected and located 181 wire failures to date, of which 81 have been confirmed by physical inspections

Annual post-tensioning investigations planned according to monitoring results with as needed tendon replacements

Predictable wire failure rate on 8.1/year has allowed for accuracte forecasting of tendon replacements, averaging 6.6/year since 1999

Identified critical area to allow for focused remediation efforts

Challenge
Prior to the installation of the monitoring system, a single post-tensioning strand erupted from the slab surface. Investigations of the state of the ground level slab revealed significant waterproofing issues on the slab edges and water ingress into the tendons. Selective, invasive, inspections on strands throughout the structure were undertaken and resulted in 164 strands replaced from a total of 850. The status of the remaining tendons was uncertain, and a comprehensive monitoring solution was desired to identify areas of active corrosion.

Solution
In order to gain further insight into the deterioration rates of the structure, a SoundPrint monitoring system was installed in February 1994. The system was the first of its kind, and the monitoring experience gained was used to refine monitoring protocols and equipment. Improvements in the technology led to significant upgrades in 2001 and 2008, without any significant interruption to the data acquisition. Overall, the system has been in continuous operation in excess of 22 years and operated at over 97% efficiency through its life.

Results
Physical investigation of detected events have been regularly undertaken by qualified consulting engineers.  The process has resulted in the following:

  1. Wire events identified and located by Pure Technologies, and reported to client and consulting engineer.
  2. Consulting engineer schedules annual investigation of existing recesses and/or creates new recesses to check condition of the strands on which the wire events may have occurred.
  3. Based upon the condition of the strands inspection, the consultant recommends tendons for replacement.

Through these inspections, 81 wire failures have been confirmed by the finding of tension deficient cables in the reported areas. The monitoring results are displayed in the chart, which shows the linear nature of the post-tensioning deterioration in the three (3) ground level slabs. This consistent rate allows the client to accurately budget tendon replacements to maintain the structural integrity while minimalizing unexpected costs and interruptions to the garage operation.