Prestressed & Post Tensioned Concrete in Scia Engineer

Published on: **Mar 4, 2016**

Published in:
Technology Business

- 1. Prestressed & Post Tensioned Concrete in Scia Engineer<br />Engineer Omar Alani<br />Product Support Engineer Scia Engineer<br />12 May 2010<br />
- 2. Overview of presentation<br />Prestress<br />Stages, TDA<br />Posttensioning<br />Conclusions<br />1<br />
- 3. Input of geometry for 1D members<br />2<br />Css<br />Boreholes<br />Stirrups<br />Reinforcement <br />Strands<br />
- 4. Types of Prestressing Units<br />3<br />EC2: <br /><ul><li>Cold-drawn wires
- 5. Indented wires
- 6. Strands
- 7. Plain round bars
- 8. Ribbed bars </li></li></ul><li>Materials of Prestressing Tendons <br />4<br /><ul><li>The system database contains all materials for prestressing tendons listed in EC2 Code and Czech standards.
- 9. The relaxation table is defined in the system database for each prestressed material.
- 10. The dialog and parameters are code and type (i.e. strand/wire/bar) dependent.
- 11. The diagrams of the relaxation values can be displayed,
- 12. The user may also edit the values in the relaxation table.</li></li></ul><li>Types of stressing <br />5<br />The stressing vs time curve type can be selected<br />
- 13. Pre tensioned general parameters<br />6<br />
- 14. Stressing bed manager<br />7<br />It is possible to define a number of stressing beds.<br />
- 15. Geometry<br />8<br />Bore holes can easily be defined.<br />
- 16. Geometry<br />9<br />Scia Engineer defines which bore holes are applicable.<br />Defined holes<br />Available holes<br />
- 17. Geometry<br />10<br />Sectional strand patterns can easily be defined.<br />
- 18. Geometry<br />11<br />Example of hollow core beam<br />
- 19. 12<br />Prestressed Concrete<br />Losses Calculated<br />Losses during tensioning due to:<br /><ul><li>Sequential prestressing (caused by the elastic deformation of concrete)
- 20. Deformation of stressing bed
- 21. Elastic deformation of the joints of segmental structures sequentially prestressed
- 22. Steel relaxation
- 23. The temperature differences between prestressing steel and the stressing bed</li></ul>Losses after transfer of prestressing (long-term losses) due to:<br /><ul><li>Steel relaxation
- 24. Shrinkage of concrete
- 25. Creep of concrete</li></ul>Losses at service due to: <br /><ul><li>Losses (changes of prestressing) caused by live loads</li></li></ul><li>13<br />Prestressed Concrete<br />Losses Calculated<br />Losses can be displayed per strand<br />
- 26. 14<br />Example 1<br />Two span continuous beam are built in two construction stages: the left span in the first stage (assigned load case 1), and the second span in the second stage (assigned load case 2).<br />
- 27. 15<br />Example 1<br />Both spans are prestressed and have a beam strand pattern defined. The left span contains 5 strands, the second one only one.<br />
- 28. 16<br />Example 1<br />Tendon stresses for load case 1:<br />In all tendons in the left beam<br />In only one strand<br />
- 29. 17<br />Example 2<br />Deformations<br />Ux strand will shorten<br />
- 30. 18<br />Example 2<br />Internal Forces<br />Normal force<br />
- 31. 19<br />Example 2<br />Stresses <br />3D stress diagram<br />
- 32. 20<br />Example 2<br />Stresses <br />Tendon stress<br />
- 33. 21<br />Post-tensioned prestressed concrete<br /> Tendon source geometry <br />Tendon source geometry <br /><ul><li>The source geometry is in fact an independently prepared shape (geometry) of the tendon.
- 34. The user may prepare the shape of the tendon just once and later assign it to numerous beams.
- 35. The source geometry is created as if intended for a straight beam. But, at the end it may be assigned even to a curved beam. The x axis (longitudinal axis) of the source geometry simply follows the x-axis of the beam regardless of the possible winding character of the beam axis.</li></li></ul><li>22<br />Post-tensioned prestressed concrete<br />Tendon source geometry <br />The tendon source geometry manager can be used to define the geometry of the tendons. <br />
- 36. 23<br />Post-tensioned prestressed concrete<br />Tendon source geometry <br /><ul><li>It is possible to draw internal tendons using graphic tools(lines, arcs).
- 37. Existing lines can be used to create tendons.
- 38. It is possible to import tendon geometry from DXF and DWG files </li></li></ul><li>24<br />Post-tensioned prestressed concrete<br />Tendon source geometry <br />It is possible to define external tendons in a way similar to internal tendons<br />
- 39. 25<br />Construction Stages<br />Phased Cross Section <br /><ul><li>Scia Engineer provides tools for defining complex construction stages.
- 40. Absences are also possible.
- 41. Phased Cross Sections is just one application of construction stages in Scia Engineer</li></li></ul><li>26<br />Construction Stages<br />Construction stages manager<br />The Construction stages manager enables you to input, review, copy, print and delete individual construction stages.<br />
- 42. 27<br />Construction Stages<br />Editing geometry of stages<br />In addition to the ability of having phased cross sections, it is possible to modify the geometry of the structure for each stage. It is possible to:<br /><ul><li>Add or remove structural members to the stage.
- 43. Add or remove supports to the stage.
- 44. Add or remove tendons to the stage.</li></li></ul><li>28<br />Construction Stages<br />Example 3<br />This T-cross-section that is made in two phases: <br />core cross section<br />composite slab<br />We shall consider three possibilities of the application of the self weight. <br />
- 45. 29<br />Construction Stages<br />Example 3<br />Situation A: <br />
- 46. 30<br />Construction Stages<br />Example 3<br />Situation B <br />
- 47. 31<br />Construction Stages<br />Example 3<br />Situation C <br />
- 48. 32<br />Construction Stages<br />Example 4<br />This example shows how construction stages can be applied to a structure geometry.<br /><ul><li>Dotted geometry is not included in the stage.
- 49. Green geometry is introduced in that particular stage.
- 50. Red geometry is removed in this particular stage.</li></li></ul><li>33<br />Construction Stages<br />Example 4<br />
- 51. 34<br />Construction Stages<br />Example 4<br />
- 52. 35<br />Construction Stages<br />Example 4<br />Results of construction stages analysis.<br /><ul><li>Results for load cases: As each construction stage is assigned one exclusive load case, the results for load cases show the contribution of the particular construction stage to the overall distribution of a given quantity.
- 53. Results for load classes: The program automatically generates result classes during the Construction Stages Analysis. Two result classes are generated for each stage: ULS class and SLS class. The classes are numbered from 1 to the number of the last analyzed stage. The results in each class show the current overall state (condition) of the structure after the particular construction stage. </li></li></ul><li>36<br />Construction Stages<br />Example 4<br />Load case LC1. This is the normal force caused by the two columns. <br />Load case LC2. This is the normal force caused only by the introduction of the beam in the middle. <br />
- 54. 37<br />Construction Stages<br />Example 4<br />The normal force for Class ST1 (ULS)<br />The normal force for Class ST2 (ULS)<br />
- 55. 38<br />Construction Stages<br />Non Linear Construction Stages<br />The Analysis of Construction Stages can be performed also as a non-linear analysis. This enables the consideration of the P-delta effect.<br />Tangent versus parallel connection of a new member<br /><ul><li>Tangent: the new member is attached to the "old" member in the direction of the tangent to the deformation line of the "old" member
- 56. Parallel: the new member is attached to the end of the deformed "old" member in the direction parallel to the direction of the new member on an undeformed structure.</li></li></ul><li>39<br />Construction Stages<br />Construction Stages –E modulus changes<br /><ul><li>In one project, the user may define several E-modulus diagrams.
- 57. Each material used in the project can have its own E-modulus diagram.
- 58. The E-modulus diagrams can be assigned to all or just some materials used in the project.
- 59. The age at installation of each member can be defined.
- 60. It is possible to assign a global time for each construction stage.</li></li></ul><li>Time dependent analysis allows the consideration of the effects of creep, shrinkage, and aging of concrete.<br />The total strain of concrete at a given time is subdivided into three parts: <br /><ul><li>The stress-produced strain
- 61. The shrinkage
- 62. The thermal expansion. </li></ul>TDA can be used in conjunction with construction stage analysis<br />Shrinkage nor thermal strains are stress-independent<br />40<br />Time Dependant Analysis<br />TDA<br />
- 63. <ul><li>Each member has it’s own history and local time axis.
- 64. All data set in the setup dialog is related to local time axis of relevant 1D member.
- 65. The origin of the local time axis (zero time) is set to the time, when the appropriate stiffness of macro is introduced into global stiffness matrix of the whole structure
- 66. The origin of local time axis is then located to global time of current construction stage. </li></ul>41<br />Time Dependant Analysis<br />Beam History<br />
- 67. <ul><li>It is possible to input negative value. In such a case the stiffness of the elements between the time of casting and the birth of macro is not included into global stiffness matrix.
- 68. In case of "phased cross-section" ‘Time of curing’is the time of curing of concrete of phase one. </li></ul>42<br />Time Dependant Analysis<br />Beam History<br /><ul><li>It is therefore possible to define line supports for 1D members at early stages, when the fresh concrete should be supported by formwork.</li></li></ul><li>The global time when each stage is applied must be defined.<br />43<br />Time Dependant Analysis<br />TDA with construction stages<br />The time axis for construction stages is merged into the global time axis<br />
- 69. The following concrete checks can be carried out in Scia Engineer<br />44<br />1D elements Prestressed Concrete Calculations <br />
- 70. Checking of limit strain (response)<br />Strain<br />Stress<br />45<br />Result examples<br />1D elements Prestressed Concrete Calculations <br />
- 71. 1D elements Prestressed Concrete Calculations <br /><ul><li>Result examples</li></ul>Checking of limit strain (response)<br />Check on screen:<br />Check in table:<br />Detailed check for each section:<br />
- 72. 1D elements Prestressed Concrete Calculations <br /><ul><li>Result examples</li></ul>Checking of interaction diagram (capacity)<br />Check on screen:<br />Check in table:<br />Detailed check for each section:<br />
- 73. Other Examples <br />Arbitrary Profiles<br />Features in SciaEngineer: Prestressed 1Delements<br />
- 74. Other Examples <br />49<br />PT Bridge<br />
- 75. Other Examples<br />PT bridge example<br />
- 76. Practical example of a bridge<br /><ul><li> 5 spans: 40 + 62 + 110 +62 + 40m
- 77. Internal and external tendons
- 78. Calculated by SCIA-customer</li></li></ul><li>
- 79. Post tension: Bridge example<br />
- 80. Post tension: PT slabs<br />
- 81. 55<br />PT Slabs<br />
- 82. PT shell elements<br />56<br />
- 83. PT shell elements<br />57<br />
- 84. 58<br />PT shell elements<br />
- 85. Worked out customer example<br />59<br />
- 86. Somereferencecustomers<br />60<br />
- 87. 61<br />Conclusions<br />Prestressing and post tensioning<br />1D and 2D elements<br />Integratedsolution in one platform<br />Easy to use interface<br />WYSIWYG<br />