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Prestressed & Post Tensioned Concrete in Scia Engineer

Prestressed & Post Tensioned Concrete in Scia Engineer

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Prestress Scia Engineer Prestress Scia Engineer Presentation Transcript

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