View
218
Download
3
Category
Preview:
Citation preview
Hybrid External PT Saves Chicago Garage
By Don Kline, P.E
1 2 3
1 2 3
1 2 3
Topics Condition Survey of Garage Structural Analysis Construction
Topics Condition Survey of Garage Structural Analysis Construction
Project Overview
Chicago Garage Engineer: Pease Borst
& Associates Contractor: Structural
Preservation Systems Specialty Engineer:
Kline Engineering & Consulting
Project Overview
Chicago GarageBuilt in 19837” banded two-way
PT flat slab with 4” drops
½” unbonded PT with extruded sheath (non-encapsulated)
Condition Survey
Locate Existing PT Using GPRMap delaminations, spalls and
cracks Investigate Condition of PT
GPR Was Used to Locate Existing PT
Condition Survey
Condition Survey
Full Depth Cracks at Mid-Span
Condition Survey
Flexure Cracking at Top of Slab Near Column
Condition Survey
Slab Spalls and Exposed PT
Condition Survey
Slab Spalls and Exposed PT
Condition Survey
Ponding with Delaminations
Condition Survey
Water Leaking Through Slab
Condition Survey
Water Leaking Through Slab
Condition Survey
Spall at Supplemental Cable
Condition Survey
Trenched Supplemental Cable
Condition Survey
Supplemental and Uniform Tendons
Failed Supplemental Distributed Tendons
Condition Survey
Opened Pockets to Inspect Condition of Strands
Condition Survey
Corrosion
Testing of Strand
Condition Survey
Uniform Strand Remains Tensioned
Condition Survey
Inspection of Grease
Condition Survey
Tested Core Samples for Concrete Strength
Banded Tendons
Distributed Tendons
Supplemental Tendons
Condition Survey
Condition Survey Summary 100% of strands on banded line 5 failed 10% - 20% of strands failed at other
banded tendon lines 100% of distributed supplemental
strands failed Original distributed tendons showed
signs of moisture in sheath and pitting of steel
Significant cracking and spalling
Condition Survey
Installation of supplemental cables could have damaged bands at high points.
Supplemental Cable Trench
Topics Condition Survey of Garage Structural Analysis Construction
Structural AnalysisWidth = 28', Span=26', Slab = 7", Col.=18" dia, D.P.=6' sq. x 4"
Structural Analysis
Slab was designed for parking live load but not for parking + snow
Supplemental distributed tendons were likely added as a retrofit soon after original construction
Conclusions From Analysis
Structural Analysis
Repair PT using conventional methods
Demo and replace top level of garage Rehabilitate using hybrid external PT
system
Owner Presented 3 Options:
Structural Analysis
Distributed Direction: New External PT to replace distributed and supplemental PT
Banded Direction: Create new shallow continuous drops with unbonded PT below existing soffit
Modeled as a 2-way flat slab
Hybrid External PT Was Selected:
External Post-Tensioning
Structural Analysis
Structural Analysis
Replace Banded Tendons from Below
Structural Analysis
Repair E/F 4-6 and Band in Col Line 5
Structural Analysis
Topics Condition Survey of Garage Structural Analysis Construction
Construction
Install DowelsRoughen Surface
Construction
Encapsulated AnchorsMultistrand Anchors
Construction
Installed Formwork
Construction
Access Ports
Pumped SCC
Construction
Stripped Formwork
Construction
Installed Deviators
Monostrand with Intumescent
Coating
Construction
Stressed Tendons
Construction
Construction
Construction
Construction
Construction
Construction
Construction
Thank You!
Recommended