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Cold Formed Steel Presentation


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A presentation I have given at the University of Southern Queensland on the design of Cold-Formed Steel Battens

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Cold Formed Steel Presentation

  1. 1. William Hutton
  2. 2. <ul><ul><li>Knowledge Gap </li></ul></ul><ul><ul><li>Specification B1.2 of the BCA </li></ul></ul><ul><ul><li>Testing and the Analysis of this Testing </li></ul></ul><ul><ul><li>The Effective Width Method </li></ul></ul><ul><ul><li>The Direct Strength Method </li></ul></ul><ul><ul><li>Results </li></ul></ul><ul><ul><li>Conclusion </li></ul></ul>
  3. 3. <ul><ul><li>Little Research conducted on effect and value of lateral and torsional restraint on hat sections. </li></ul></ul><ul><ul><li>Torsional restraint of corrugated roof cladding profiles. </li></ul></ul><ul><ul><li>DSM on the hat sections, to allow them to become classified as pre-qualified sections. </li></ul></ul>
  4. 4. <ul><ul><li>States that ALL metal roofing systems, specifically metal roof cladding, its connections and its immediate supporting members, used in cyclonic regions shall be tested using Low-High-Low (LHL) test regime. </li></ul></ul>Sequence No. of Cycles Load A 4500 0 to 0.45Pt B 600 0 to 0.6 Pt C 80 0 to 0.8 Pt D 1 0 to 1.0 Pt E 80 0 to 0.8 Pt F 600 0 to 0.6 Pt G 4500 0 to 0.45 Pt
  5. 5. <ul><ul><li>Batten Web </li></ul></ul><ul><ul><ul><li>Upward dooming of the screw hole </li></ul></ul></ul><ul><ul><ul><li>2 to 3 cracks forming perpendicular to the hole </li></ul></ul></ul><ul><ul><li>Batten Feet </li></ul></ul><ul><ul><ul><li>Screw tears through batten feet, commencing at the feet-web junction </li></ul></ul></ul>
  6. 6. Batten Type No. of Tests Factor of Variability, kt Applied Load, Pt Ultimate Limit State Strength 40x0.75 4 1.50 5.37 3.58 64x0.75 1 1.79 4.90 2.73 64x1.00 1 1.79 5.21 2.91
  7. 9. <ul><ul><li>Applies the Finite Strip Method to the given profile. </li></ul></ul><ul><ul><li>Provides Load factors for each buckling mode. </li></ul></ul><ul><ul><li>Provides the yielding moment, My </li></ul></ul><ul><ul><li>Provides the yielding compressive force, Py </li></ul></ul><ul><ul><li>These values are then used to calculate the Local and Elastic Buckling stress </li></ul></ul>
  8. 10. Local Buckling Load Factor = 0.71 Half-Wavelength=1.6” Distortional Buckling Load Factor = 6.39 Half-Wavelength=21.0”
  9. 11. <ul><ul><li>Utilises the elastic buckling stress calculated from the output of CUFSM and Gross Section Properties of the profile. </li></ul></ul><ul><ul><li>Analyses the batten for a given span and allows the the effects of lateral restraint, torsional restraint and load height on the batten to be considered. </li></ul></ul><ul><ul><li>Adopted Kry=1000kN/rad and krx=0kN/rad. </li></ul></ul>
  10. 13. <ul><ul><li>Test Batten Connection to LHL regime </li></ul></ul><ul><ul><li>Analysis results as per AS/NZS1170.0 </li></ul></ul><ul><ul><li>Calculate gross section properties. </li></ul></ul><ul><ul><li>Calculate elastic buckling stresses in CUFSM </li></ul></ul><ul><ul><li>Calculate load-span capacity using PURLIN. </li></ul></ul><ul><ul><li>Combine testing and numerical analysis to determine the load-span capacity using Spread Sheet program and develop the load-span tables. </li></ul></ul>
  11. 14. Load-Span Capacity table for 40x0.75mm Batten Span 2 Batten Screws 4 Batten Screws w* u,uplift w* u,down w* u,uplift w* u,down 600 4.692 4.692 Cladding Connection Fatigue Strength 4.692 4.692 Cladding Connection Fatigue Strength 900 3.616 3.616 Batten Feet Fatigue Strength 4.692 4.692 Cladding Connection Fatigue Strength 1200 2.712 2.712 Batten Feet Fatigue Strength 3.187 3.526 Uplift: DSM Analysis. Downthrust: Connection Fatigue Strength 1500 2.030 2.170 Uplift: DSM Analysis, Downthrust: connection Fatigue Strength 2.030 2.351 Uplift: DSM Analysis. Downthrust: Connection Fatigue Strength
  12. 15. <ul><ul><li>The DSM provides better results than the EWM. </li></ul></ul><ul><ul><li>The design procedure allows for quick efficient batten design. </li></ul></ul><ul><ul><li>For short spans, the connection capacity governs thus LHL testing critical </li></ul></ul>
  13. 16. Thank You