L1 4 L ENGINEERING LTD. Wall Engineering Ltd. Building Science & Restoration 408 - 32 Avenue NW Calgary AB, T2M 2P9 Canada www.wallengineering.ca March 13, 2017 Riverside Tower Condominium Corporation C/o Connelly & Company Property Management #204, 2723 37 Ave NE Calgary AB, T1Y 5R8 Attn: Mr. Marty Connelly Email: [email protected]Dear Mr. Connelly, RE: Riverside Tower - 145 Point Drive NW, Calgary Parkade Post Tensioning System Update WalI#: 10110.0004 In response to your request, Wall Engineering Ltd. performed update testing of the post- tensioning system at the above referenced property in February 2017. The primary intent of the testing is to monitor any changes in tension deficiencies within the existing test sample. Test results obtained and recommendations provided in this report are based on limited sampling in select areas. The following provides a summary of our findings. 1,0 BACKGROUND INFORMATION Unbonded post-tensioned strand systems are a common form of structural reinforcing that was widely used throughout the 1970's to 1980's. The system relies on high strength steel strands to reinforce a thin concrete slab and each strand is comprised of seven (7) steel wires encased in grease and plastic sheathing. The structural strength of this system relies on the draped profile installed during original placement of the strands, which sinusoidally extends over each of the columns/beams. Once the slab has cured, the strands are hydraulically tensioned, which straightens the draped profile (i.e. lifting the concrete slab) and engaging the slab to achieve the structural design capacity. Each strand that is embedded within the concrete incorporates steel anchors at the end of the slab. These anchors can be susceptible to moisture ingress depending on the degree of exposure and quality of waterproofing during original construction. Post construction moisture ingress can also occur through deficient waterproofing. The deterioration process includes the emulsification or breakdown of grease, surface corrosion of wires, pitting/sectional steel loss, stress corrosion cracking of the individual wires and in many cases fracture of one or more of the wires (loss of tension/tension deficiency). The rate of Wall Engineering Ltd. Riverside Tower 145 Point Drive NW, Calgary Wall#: 10110.0004 Page 1 of4
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Wall Engineering Ltd. Calgary AB, T2M 2P9 Canada Building ... · Building Science & Restoration 408 - 32 Avenue NW Calgary AB, T2M 2P9 Canada ... strand slippage from the anchors,
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L14L ENGINEERING LTD.
Wall Engineering Ltd. Building Science & Restoration