Case Study: Post Tension Foundation Failure Repair
In my last blog, I discussed in general some common things we are seeing in post tension foundation failures. In this blog I will discuss one case in particular that illustrates this.
In 2016, we were contacted by a home owner with serious distress in her home. The initial observations of the home included:
- A horizontal crack in the perimeter of the foundation on the east wall
- A horizontal crack of the floor matching this location on the floor parallel with the east wall
A complete Level B Investigation was ordered and when complete noted the following additional items:
- Badly deteriorated concrete on the east wall
- Badly rusted rebar, cables and termination components
- The east side of the home had noticeable settlement
- The dead side of the cables showed cable protrusion indicating cable failure
- Horizontal wall movement of the east wall moving away from the rest of the house
- The concrete had a noticeable horizontal cold joint
- The concrete was of poor quality with extreme aggregate separation
With the information, and with the help of a local registered engineering specialist for post tensioned systems, Rob Hamblin PE, we put together the following repair plan:
- First shore up the structure both vertically and horizontally
- Detention the cables in the affected area
- Remove all deteriorated concrete and all concrete around oxidized steel components
- Place new concrete that was stronger than the original
- Install new cables with encapsulation system to protect the steel components from oxidization
- Underpinning was recommended to compensate for further downward settlement that occurred during operations
Once completed the shoring was removed and the residence could have the cosmetic restoration completed and the residence could be fully occupied.
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