a precast supplier perspective · a precast supplier perspective . al patel, pe clark-nexsen rodney...
TRANSCRIPT
![Page 1: A PRECAST SUPPLIER PERSPECTIVE · A PRECAST SUPPLIER PERSPECTIVE . Al Patel, PE Clark-Nexsen Rodney Davis, PhD, PE Bayshore Concrete Products ... NCHRP 496 EQUATION . CREEP COEFFICIENT](https://reader031.vdocuments.mx/reader031/viewer/2022022523/5b3879297f8b9abd438d4565/html5/thumbnails/1.jpg)
THE CONTINUITY CONUNDRUM A PRECAST SUPPLIER PERSPECTIVE
Al Patel, PE Clark-Nexsen Rodney Davis, PhD, PE Bayshore Concrete Products Fatmir Menkulasi, PhD, PE La-Tech University JP Binard, PE Bayshore Concrete Products
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HISTORY
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CURRENT CODE PROVISION
• AASHTO LRFD SPECIFICATIONS:
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CLAUSE:
• 50% Live Load
• Temperature Gradient
• Superimposed Comp DL
• Creep
• Shrinkage
• Settlement, not considered
COMPRESSIVE?
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DESIGN
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PROBLEM?
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PARAMETERS:
• PCBT 45, 69, & 95
• Solar Radiation, Zone 3
• 2 Span, 3-Span, 4-Span
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THERMAL
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2-SPAN: THERMAL + LL , + SDL
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3-SPAN: THERMAL + LL , + SDL
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4-SPAN: THERMAL + LL , + SDL
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SIMPLIFIED CLAUSE:
• 50% Live Load
• Temperature Gradient
• Superimposed Comp DL
• Creep
• Shrinkage
• Settlement, not considered
COMPRESSIVE, TYPICAL
INVESTIGATE
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CREEP & SHRINKAGE
• AASHTO LRFD SPECIFICATIONS
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V/S RATIO
AASHTO LRFD, SIMPLIFIED
NCHRP 496 EQUATION
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CREEP COEFFICIENT
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SHRINKAGE STRAIN
COMMENTARY EQUATION RESULTS ARE CONSISTENT WITH THIS STATEMENT
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EXAMPLES:
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EXAMPLES:
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EXAMPLES:
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EXAMPLES:
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MEASUREMENTS:
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EXAMPLES:
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MEASUREMENTS:
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CURE TO MATURITY:
REDUCE COEFFICIENT TO < 1.0 • Increase t and f’ci
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CONCLUSION:
• The 90 Day Clause of AASHTO LRFD may be relaxed for common PCBT span to depth ratios in solar radiation zone 3.
• Thermal + 50% LL + SDL for standard cases is already compressive and may be excluded in the determination of compression at the bottom flange/diaphragm interface
• Creep and Shrinkage using modern day concretes and the appropriate formulas allow continuity to be established at a younger age.
• If continuity needs to be established at a young age, increase release strength and cure time.
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QUESTIONS: