tendon blowouts and eruptions, causes and repairs convention... · 2009 pti technical conference...
TRANSCRIPT
PTI 2009 Technical Conference & Exhibit – Portland, OR
TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS
by
Douglas Sarkkinen, PE, SE
Principal
Kramer Gehlen & Associates, Inc.
Vancouver, WA
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 1 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
KGA projects
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 2 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
OVERVIEW
• Post – Tension Flat Plate Structures – Unbonded Monostrand
• Robust Structural System
• Millions of square feet of construction each year
• Problems can occur – during and after construction is completed
• Repairs can be done
• Designers/Contractors can learn from past problems
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 3 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Presentation Covers:
• 4 types of Problems
• Examples – Case studies
• Causes
• Repairs
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 4 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
PROBLEM TYPES
Type 1 ‐ Anchorage Zone Blowouts
Type 2 ‐ Internal Slab Blowouts
Type 3 ‐ Tendon Eruption
Type 4 ‐ Surface Spalls at Tendons
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 5 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Type 1 ANCHORAGE ZONE BLOWOUT
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 6 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 7 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 8 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 9 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 10 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Possible Causes
‐ Lack of bursting reinforcing steel‐ Bursting reinforcing steel misplaced(laying on the side or
too far away)‐ Low strength concrete‐ Voids or rock pockets in concrete‐ Offset anchorages allowing a head in the anchorage zone
of another.‐ Inadequate confining steel in thin slabs‐ Tendons located at a slab corner without adequate
confining reinforcing
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 11 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
REPAIRS
• Safety ‐ detensioning
• Investigation
• Evaluation
• Cleaning – chipping away to sound concrete
• New anchorage heads
• Adequate Confinement
• Replace concrete and restress
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 12 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Type 2 ‐ INTERNAL SLAB BLOWOUTS
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 13 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 14 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 15 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 16 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Causes
• Sharp tendon sweeps/near surface
• Inadequate confinement
• Stage Stressing not done
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 17 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Repairs:
• Investigation ‐ Evaluation
• Situation Specific
• Repair in‐place or completely rebuild
• Extent of tendon damage
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 18 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Type 3 – Tendon Eruption
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 19 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 20 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 21 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Causes
• Anchorage slip
• Corrosion – tendon breakage
• Saw cutting or drilling
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 22 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Repairs
• Investigation – Evaluation
• Often is neglected if only (1) tendon
• Replace tendon with 3/8” diameter tendons
• Patch Concrete
• Mitigate penetration of water
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 23 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Type 4 – Surface Spalls
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 24 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 25 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 26 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 27 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 28 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 29 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Causes
• During construction – reverse curvature
• Possible voids
• Sometimes unknown
• Post‐Construction ‐ water
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 30 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Repairs
• Investigation – Evaluation
• Corrosion
• Mitigate water Problem
• Clean and patch
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 31 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 32 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 33 of 35
PTI 2009 Technical Conference & Exhibit – Portland, OR
Summary
• Robust system – but problems can occur
• Most causes are identifiable, but not always
• Repairs can be made
• Details, Details, Details.
2009 PTI Technical Conference TENDON BLOWOUTS AND ERUPTIONS CAUSES AND REPAIRS Douglas Sarkkinen, PE, SE
© Copyright Post-Tensioning Institute all rights reserved. Page 34 of 35