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LOAD PATH DESIGNATION

LOAD PATH DESIGNATION. 2. 3. 4. 5. 1. A. B. C. D. E. F. Y. X. G. POST-TENSIONING IN BUILDING CONSTRUCTION PRINCIPAL ANALYSIS ASSUMPTIONS. Gross cross-section Elastic Analysis Redistribution of moments due to limited plasticity.

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LOAD PATH DESIGNATION

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  1. LOAD PATH DESIGNATION 2 3 4 5 1 A B C D E F Y X G

  2. POST-TENSIONING IN BUILDING CONSTRUCTION • PRINCIPAL ANALYSIS ASSUMPTIONS • Gross cross-section • Elastic Analysis • Redistribution of moments due to limited plasticity

  3. POST-TENSIONING IN BUILDING CONSTRUCTION • PRINCIPAL ANALYSIS METHODS • Equivalent Frame Method (EFM) • Simple Frame Method (SFM) • Finite Element Method (FEM)

  4. NONPRISMATIC IDEALIZATION OF COLUMNS NEUTRAL AXIS OF SLAB/BEAM DROP PANEL STRUCTURAL SYSTEM LINE h h c o I COLUMN co N.A. (b) COLUMN MODEL (a) COLUMN BETWEEN TWO SUPPORTS

  5. Over the last four decades millions of buildings are designed using Equivalent Frame Method Features of Equivalent Frame Method • Nonprismatic representation of members • Allowance for biaxial action through adjustment in column stiffness

  6. PROCESSING OF ANALYSIS RESULTS Load Combinations • Serviceability • Dead, Live, Prestressing • Strength • Dead, Live, Hyperstatic • Transfer of prestressing • Dead, Live, Prestressing

  7. PERMISSBLE STRESS VALUES Maximum Compressive Maximum Tensile Stress Stress MPa (psi) MPa (psi) Initial Stress 0.60 f 'ci 0.60 f 'ci 0.25 f 'c 3 f 'c Ö Ö Condition 0.50 f 'c 6 f 'c Ö Ö Service Condition 0.45 f 'c 0.45 f 'ci (two - way system) 1.00 f 'c 12 f 'c Ö Ö (one - way system)

  8. HYPOTHETICAL STRESSES FOR CODE COMPLIANCE TRIBUTARY DIRECTION OF FRAME SLAB DESIGN SUPPORT SECTION LINE LOCATION COLUMN OF STRESS CHECK (a) PARTIAL PLAN OF SLAB DESIGN SECTION (b) ELASTIC SOLUTION DISTRIBUTION OF MOMENT (c) SMEARED DISTRIBUTION OF STRESS

  9. REDISTRIBUTION OF ELASTICALLY CALCULATED MOMENTS PLASTIFICATION REGION (a) BEAM-FRAME WITH FINITE SUPPORT WIDTHS PLASTIFICATION REGION (b) SLAB/BEAM WITH ZERO SUPPORT WIDTHS PERMISSIBLE LOCATIONS OF PLASTIFICATION FOR REDISTRIBUTION

  10. SUPPORT MOMENTS AND PERMISSIBLE RANGES OF THEIR REDISTRIBUTION EQUAL OFFSETS ELASTIC MOMENT UPPER VALUES REDISTRIBUTION RANGE LOWER VALUES (a) SUPPORT MOMENTS LIMITED BEAM/SLAB PLASTIFICATION COLUMN (b) REGION OF LIMITED PLASTIFICATION AT SUPPORTS

  11. REDISTRIBUTION BASED ON LOWEST EQUAL MOMENTS SELECTED EQUAL VALUES REDISTRIBUTION RANGE SELECTED REDISTRIBUTED MOMENTS

  12. SIMPLIFIED, BUT CONSERVATIVE SECTION DESIGN a a d d e e PT REBAR • IF • f’c > 4000 psi (f’c 28 Mpa) • P/A < 250 psi (P/A  1.72 Mpa) • a/de < 0.4 • Tendon length < 125’ (38 m) single stressing • Else, double stressing up to 250’ (76 m) THEN • For SLABS • fpu = 215 ksi (1500 MPa ), if span < 35’ (11 m), else 195 ksi (1350 MPa ) • For BEAMS • fpu = 205 ksi (1400 MPa ), if span < 35’ (11 m), else 190 ksi (1300 MPa )

  13. DROP CAPS USED FOR PUNCHING SHEAR

  14. SELECTED SHEAR REINFORCEMENT OPTIONS POSITIONING BAR MIN LENGTH 8 b d WELD b WELDED d HEAD (i) (ii) (a) TWO SHEAR STUD OPTIONS POSITIONING TOP BAR BOTTOM HEAD ON SPACER (c) I-SECTION SLICE (b) SINGLE STUD PLACEMENT STUD ANCHOR STRIP HOLES FOR WELD ATTACHMENT TO FRAMEWORK (d) STUDS ON STRIP

  15. PLAN - TYPICAL ARRANGEMENT OF STUD SHEAR REINFORCEMENT AROUND COLUMN ANCHOR STUD STRIP HOLES FOR ATTACHMENT TO FRAMEWORK WELD STUD SHEAR REINFORCEMENT STRIP COLUMN STUD FORMWORK

  16. PUNCHING SHEAR REINFORCEMENT ELIMINATES DROP CAPS

  17. EXAMPLES OF SHEAR STUD REINFORCEMENT

  18. PUNCHING SHEAR REINFORCEMENT ELIMINATES DROP CAPS

  19. Thank you for your attention.

  20. Slide Log

  21. POST-TENSIONING IN BUILDING CONSTRUCTION • OK

  22. POST-TENSIONING IN BUILDING CONSTRUCTION DIMENSIONS AND SIZING OF MEMBERS • Support spacing • Slab thickness • Beam dimensions

  23. Load Combination • Serviceability • Use balanced loading • Use same load factor as dead load • Safety • Use hyperstatic (secondary moments) • Use load factor 1

  24. CONSTRUCTION SEQUENCE • Stressing of beam and slabs prior to construction of columns and walls above

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