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Session 6 (B) Durability Assessment of Structures

Session 6 (B) Durability Assessment of Structures. Dr. Paul J. Tikalsky, P.E., FACI The Pennsylvania State University USA. Durability Based Design. 6 steps Defining environmental exposure Defining the desired life Defining required performance Modeling performance vs. exposure vs. life

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Session 6 (B) Durability Assessment of Structures

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  1. Session 6 (B)Durability Assessment of Structures Dr. Paul J. Tikalsky, P.E., FACIThe Pennsylvania State University USA

  2. Durability Based Design • 6 steps • Defining environmental exposure • Defining the desired life • Defining required performance • Modeling performance vs. exposure vs. life • Specifying materials and methods • Inspection of construction Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  3. Environmental Exposure • Chemical Exposure • Sulfate concentration • Cation (Ca, Mg, Na) • Chloride concentration • Carbon dioxide or monoxide concentration • Acid concentration and type • Other chemical concentrations Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  4. Defining the Service Life Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  5. Performance Characteristics Standard Test Method HPC performance grade 1 2 3 CP Chloride penetration, Coulombs AASHTO T 277 4000X>2500 2500X>1500 1500>X CS Compressive Strength, MPa AASHTO T 22 24X<32 32X<55 55X<82 SD Strength ratio 28 day fc 7 day fc AASHTO T 22 1.15 1.33 1.45 SU Sulfate resistance (expansion) ASTM C 1012 X<0.10% At 6 months X<0.10% At 12 months X<0.10% At 18 months Defining Performance Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  6. Performance, Exposure & Life Based on 75 year life expectancy Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  7. Specifying Materials & Methods • Very difficult to use pure performance based specifications • Prescription of best practices are necessary • Prequalification of materials • Prequalification of Contractor • QC/QA Plan and implementation • Training and certification of workforce Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  8. Inspection • Assessment based design must be verified by inspection • Inspection is essential to improve the models from laboratory to field performance. Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  9. Life Cycle Design • How can designers choose a terminal time, Tt, considering….. • real estate developers are designing for both obsolescence • The infrastructure environment (bridges, government building, utilities) are designing for extended life • Everyone is designing for sustainability Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  10. Consensus Research Direction • How should interactions between different durability effects be addressed? • What type of data is needed to develop reasonable models? Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  11. Models and Design Decisions • Do sufficient time-dependent models exist? Which one’s should be used? • Are variations in the variables sufficiently known to use simulation based design programs? • What training needs to be conducted to assist designers in making life-cycle design decisions? Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  12. Prof. Paul J. Tikalsky, P.E., FACIPenn State University Transportation Infrastructure Lab. 3127 Research DriveState College, PA 16801 USATikalsky@psu.edu Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  13. Chloride Penetration Model • C (x,t) = chloride concentration at depth x after time t • Co = equilibrium chloride concentration at the surface of the concrete • erf = the error function, a standard mathematical function • Dc = chloride diffusion constant. Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  14. Permeability • K C= permeability coefficient • Q = rate of flow • H/L = ratio of head of fluid to percolation length • A = cross section area under pressure Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  15. Subsidence Cracking Model • p = probability of settlement cracking • y = 1.37 - 0.58x1 - 0.56x2 + 0.27x3 [inch] • = 1.37 - 0.023x1 - 0.56x2 + 0.011x3 [mm] • x1 = concrete cover • x2 = concrete cover / bar size • x3 = concrete slump Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  16. Chloride Diffusion Model C(x,t) = chloride concentration t = time x = depth Co = surface chloride concentration Dc = chloride diffusion constant erf = Error Function Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

  17. Chloride Concentration and Diffusion Constant

  18. Chloride Concentration and Cover Depth

  19. Chloride Concentration vs Time Euro-SiBRAM’2002 Prague, June 24 to 26, 2002, Czech Republic

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