Multiframe intro

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آشنایی با نرم افزار Multiframe
وبلاگ مهندسی دریا
kmsu.mihanblog.com

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Multiframe intro

  1. 1. Contact Information• Philip Christensen• Formation Design Systems• philc@formsys.com• www.formsys.com• www.formsys.com/academic• Password frog5cove
  2. 2. Tutorial Program1. Introduction to Multiframe2. Structural modeling & intro to Section Maker3. Loads and load cases – sample problem4. Understanding results – sample problem5. Assignment6. Assignment
  3. 3. Background to Multiframe• What is Multiframe?• Structural analysis and design software• Linear 3D beam elements• “Stick and Ball” model of primary structure• Good for framed structures, less suited to slab and wall structures
  4. 4. Using Multiframe• Setup – Units – Size• Basic Concepts – Global axes – Local axes – Section Axes• Frame, Load, Plot windows
  5. 5. Steps in structural analysis1. Geometry2. Connectivity3. Materials/Section Properties Frame Window4. Member Types5. Restraints6. Loads Load Window7. Analysis Plot Window8. Results
  6. 6. Geometry• Joint coordinates• Member lengths• Sketch in Frame window• Modify by double click• Modify in Data window
  7. 7. Connectivity• Defines which members are connected to which other members• Done automatically as you draw in Frame window• Can be reviewed in Member table in Data window
  8. 8. Materials/Section properties• Define size and materials of structural members• Sections are stored in Library• Custom sections are possible• Section Maker helps with section property calcs• Applied to members in the Frame window
  9. 9. Member Types & Orientation• Section Orientation• Also known as “beta” angle• Member releases define pins at ends of members• Applied to members in the Frame window
  10. 10. Restraints• Define how structure is “held down”• Commonly pinned or rigid• Apply to joints in Frame window• Custom restraints are possible
  11. 11. Loads• Automatic self weight• Loads on joints – Point loads or moments• Loads on members – Point or Distributed• Consider a number of loading conditions or cases• Factored combinations of load cases
  12. 12. Analysis• Static linear (1st order) 1st Order• Static nonlinear – (2nd order, large deflection) Load – P. ∆ and P. δ 2nd Order• Dynamic modal• Dynamic time history Deflection
  13. 13. Results• Deflections• Actions – Forces, moments• Stresses – Axial, bending, shear• Diagrams in Plot window• Tables in Results window• NB Deflection diagram is exaggerated
  14. 14. Sample Problem• 2D Truss to carry 1 x 20kN load at middle of a 10m span• Goals are – – Deflection not greater than 40mm – Axial stress not greater than 100MPa• How light can you make it? – Use Data Window/Sections table to check weight 20kN 10m
  15. 15. Section Maker• Utility for calculating properties of a structural shape• Weight, Area, Ix, Iy, J, E, G are required for Multiframe• Others are useful for stresses and design
  16. 16. Using Section Maker• Placing Sections• Placing Shapes• Drawing Shapes• Importing Shapes• Properties• Limitations – No overlapping shapes – J approximate in some cases
  17. 17. Structural Modeling1. Use clipping and masking to manage more complex models2. Importing DXF3. Modeling trusses4. Modeling frames5. Common errors
  18. 18. Data Import - DXF• DXF - AutoCAD, Microstation etc• Import 3D DXF from any CAD system• Each LINE/POLYLINE segment becomes a member in Multiframe• No arcs in polylines• Don’t use local extrusion axes• Make sure any BLOCKs are exploded prior to export• Check units in DXF file are consistent with Multiframe• Use rotate command after import if necessary
  19. 19. Modeling Trusses• Trusses resist loads using axial actions only – bending• Structure must be completely triangulated – Be careful in 3D• Set joint types to pinned• Usual to apply only joint loads• Review deflections and axial forces in results – Tension and compression
  20. 20. Modeling Frames• Frames resist loads using combination of bending and axial forces• Columns carry vertical loads as axial forces and resist horizontal loads by bending• Beams resist vertical loads by bending• Braces resist transverse loads by axial tension or compression
  21. 21. Common modelling errors• Setting all joints to be restrained – Only the joints at the foundations should be restrained• Drawing a member through a joint – Every member must run from joint to joint. Subdivide if necessary.Check by selecting the member.• Duplicating members so they touch but are not connected to other members – Check using animation• Getting loading units wrong
  22. 22. Load Cases• Common load cases – Self weight (Permanent) • Multiframe commands – Dead load (Permanent) – Add Self Weight – Live load (Imposed) – Add Static Load Case – Wind load – Add Combined Load Case – Load combinations• Load magnitudes are determined using AS1170 or from first principles
  23. 23. Dead Load• Loads which are permanently applied to the 1 Pa = 1 N/m2 structure• 1 N = 1 kg x g For joint loads, consider area which will contribute load to that joint g = 9.8 (~10)• For member loads, consider area which will load that member• For trusses its common to apply joint loads P B w L P (N) = B (m) x L (m) x w (Pa)
  24. 24. Live Load• Loads which are temporarily applied to the 1 Pa = 1 N/m2 structure• 1 N = 1 kg x g e.g. Pedestrians on the walkway• w determined from no. of pedestrians per sq g = 9.8 (~10) metre and average weight per person P B w L P (N) = B (m) x L (m) x w (Pa)
  25. 25. Wind Load• AS1170 prescribes wind load calculations• q = 0.5 * ρ * V2 * Cf – q is design wind pressure Pa – ρ is air density = 1.2 kg/m3 D – V is wind speed in m/s (assume 40 m/s) – Cf is a shape factor (default to 1.0)• Total load on member = L * D * q L• Load per unit length w = q * D – D = depth of member perpendicular to air flow• Direction of load is parallel to air flow
  26. 26. Loading Areas• Tributary area – Use to transfer pressure to a member supporting an area – Be careful with units – More complicated patterns with 4-way supported slabs W=P.d kN/m where P is in kPa and d is in metres
  27. 27. Sample Problem Tree top walk
  28. 28. Tree top walk
  29. 29. Tree top walk
  30. 30. Tree top walk
  31. 31. PlanWorked Example• Tree Top Walk Truss, Walpole WA• Length 60m, max depth 4m, max width 3.0m, width at ends 1.0m• Bottom chord 50mm rod, top chords CHS168x4.8, transverse members RHS150x50x4, bracing CHS102x4• www.donaldsonandwarn.com.au Side Elevation
  32. 32. Worked Example Loads• Consider self weight, dead weight, live load and wind.• Dead weight comes from 100mm thick jarrah walkway• Dead weight also comes from side railings at 70kg/m• Live load comes from human traffic• Wind load as per AS1170• Self+Dead+Live+Wind• Assume load is only applied at nodes of truss
  33. 33. Worked Example Dead Loads• Self Weight using Add Self Weight load case• Jarrah decking, 6m segment x 0.5m wide x 0.1m thick= 0.6m3• Density of Jarrah is 800kg/m3 = 480kg = 4.8kN• 6m handrail @ 70kg/m = 420kg = 4.2kN• Total 9kN per node. 9kN 9kN 6m
  34. 34. Worked Example Live Loads• People standing on deck• 6m segment x 0.5m wide= 3m2• Average person 70kg, one per square metre• 3 x 70 = 210kg = 2.1kN per node 2.1kN 2.1kN 6m
  35. 35. Worked Example Wind Loads• q = 0.5 * ρ * V2 * Cf – =0.5 x 1.2 * 40 x 40 = 960 Pa (~1kPa)• Total load on member = L * D * q• Load per unit on eg top chord• w = q * D = 1 * 0.16 = 0.16 kN/m• Repeat for each member of different depth• Direction is perpendicular to length of truss
  36. 36. Analysis• Static linear (1st order) 1st Order• Static nonlinear – (2nd order, large deflection) Load – P. ∆ and P. δ 2nd Order• Dynamic modal• Dynamic time history Deflection
  37. 37. Results• Deflections, forces, moments, stresses• Diagrams in Plot window• Tables in Results window• Deflection diagram is exaggerated
  38. 38. Deflection Plots• Exaggerated display of deflected shape• Can exaggerate more or less using Scale item in Plot dialog in Display menu• Can set to true scale of displacement using scale of -1• Can overlay an action or stress as a color on the diagram• Can render the deflected shape• Can animate the deflection shape and save as an avi movie
  39. 39. Assignment• Write the report as a self-contained document – Note any required external documents• Use simple, annotated drawings to clarify• Explain all assumptions• Display intermediate as well as final working of calculations and show all units• Make sure units are consistent• Use clear, simple, concise, professional language
  40. 40. Student Models 1
  41. 41. Student Models 2
  42. 42. Student Models 3
  43. 43. Student Models 4
  44. 44. Student Models 5
  45. 45. Student Models 6
  46. 46. Student Work 1
  47. 47. Student Work 2
  48. 48. Student Work 3
  49. 49. Student Work 4
  50. 50. Student Work 5
  51. 51. Student Work 6
  52. 52. • © Formation Design Systems Pty Ltd• PO Box 1293 Fremantle WA 6959• Tel +61 8 9335 1522 Fax +61 8 9335 1526• Email: philc@formsys.com• Web Site: www.formsys.com

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