a selection of features in more detail - … nordic...2016 / 5 prestress prestressing applications...
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A Selection of Features in more
Detail
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Prestressing
Example - Precast Pre-tensioned Beam
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2016 / 3 Prestress
Prestressing
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2016 / 4 Prestress
Prestressing
Different types of pre-stressing
• Internal / external tendons.
• Bonded / unbonded tendons
• Pre- and post-tensioning.
• For beam- & shell –elements
• In haunched beam/plate
Definition
• 3D Geometry (spline, polyline, etc.)
• Free-shape modelling in AutoCAD
• Graphical editor
• Eccentric duct position.
• Integrated in CABD (= axis-based)
Modelling/Analysis
• Detailed loss calculation, including friction, wedge slip,
time-dependent effects etc.
• Construction sequence
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2016 / 5 Prestress
Prestressing
Applications for Bridges/Buildings:
• Longitudinal post-tensioning
• Transversal post-tensioning
• Post-tensioned slabs
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2016 / 6 Prestress
Prestressing
Applications for Bridges/Buildings:
• Local and global
• Tension band for arches
• Free cantilever with many stages
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2016 / 7 Prestress
Prestressing
Applications for Bridges/Buildings:
• Precast post-tensioned beams
• Precast pre-tensioned beams
• Simple or composite section?
• Construction stages?
• Short and long term losses?
• Force transfer length?
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Example – Precast Pre-tensioned Beam
2016 / 8 Prestress
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2016 / 9 Prestress
Example – Precast Pre-tensioned Beam
Simple or composite section?
Composite: After the beam is erected to its final position, it will be completed with
an in-situ deck. The cross section report from Module Aqua will look like this:
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2016 / 10 Prestress
Example – Precast Pre-tensioned Beam
Construction Stages?
• Yes: We will use construction stages so that we can differentiate between
the precast section and the end section including the slab portion of the
beam, as different loads act on different stages.
• It is important to define the construction sequence before starting with
modelling. The construction sequence might be something like this:
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2016 / 11 Prestress
Example – Precast Pre-tensioned Beam
Short term (immediate) losses?
• Elastic shortening of concrete Must be taken into account by using a factor
• Slip at anchorages immediately after prestressing Only for post-tensioning
• Friction between tendon and tendon duct, and wobble effect Only for post-tensioning
Long term (time dependent) losses?
• Creep and Shrinkage of concrete Will be calculated automatically in CSM
“creep steps”
• Relaxation of prestressing steel Will be calculated automatically in CSM
“creep steps”
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2016 / 12 Prestress
Example – Precast Pre-tensioned Beam
Force transfer length?
• The transfer length of prestressing
force is the length of cable measured
from the end of the prestressed
element along which the effective
stress due to prestressing is
transferred to the concrete. The force
of pre-tensioning in the concrete
linearly increases along the transfer
length from a value of 0 at the end of
the element to the effective value of
prestressing stress on the length L
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2016 / 13 Prestress
k
Workflow:
1- Open new project
2- Define required materials
3- Define the prestressing system
4- Open SOFiPLUS for model creation
5- Create a new cross section in the “Cross Section Editor”
6- Create structural lines
7- Create support conditions
8- Create tendons
Example – Precast Pre-tensioned Beam
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2016 / 14 Prestress
k
Workflow:
9- Define and assign loads
10- Export model to SSD
11- Control the prestressing forces and immediate losses
12- Define the construction stages with task CSM
13- Calculate other required tasks
14- Control results
Example – Precast Pre-tensioned Beam
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2016 / 15 Prestress
k
Example – Precast Pre-tensioned Beam
Workflow: Special considerations
1- Open new project
2- Define required materials
3- Define the prestressing system
4- Open SOFiPLUS for model creation
5- Create a new cross section in the “Cross Section Editor”
6- Create structural lines
7- Create support conditions
8- Create tendons
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Example – Precast Pre-tensioned Beam
2016 / 16 Prestress
k
Workflow: Special considerations
When working with composite sections, different material should be used for the
different cross section parts.
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2016 / 17 Prestress
k
Example – Precast Pre-tensioned Beam
Workflow: Special considerations
1- Open new project
2- Define required materials
3- Define the prestressing system
4- Open SOFiPLUS for model creation
5- Create a new cross section in the “Cross Section Editor”
6- Create structural lines
7- Create support conditions
8- Create tendons
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Example – Precast Pre-tensioned Beam
2016 / 18 Prestress
k
Workflow: Special considerations
Insert a new used defined prestressing system. In the Construction tab, set all values
which are relevant for the calculation of immediate losses in post-tensioning to zero.
Set the inner and outer diameters of the duct to the same value as “real” the tendon
diameter.
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2016 / 19 Prestress
k
Example – Precast Pre-tensioned Beam
Workflow: Special considerations
1- Open new project
2- Define required materials
3- Define the prestressing system
4- Open SOFiPLUS for model creation
5- Create a new cross section in the “Cross Section Editor”
6- Create structural lines
7- Create support conditions
8- Create tendons
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Example – Precast Pre-tensioned Beam
2016 / 20 Prestress
k
Workflow: Special considerations
Define a new solid section. Make sure you define two construction stages, according to our
stage definition: CS10 for the prefabricated part and CS40 for the cast in place portion
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2016 / 21 Prestress
k
Example – Precast Pre-tensioned Beam
Workflow: Special considerations
1- Open new project
2- Define required materials
3- Define the prestressing system
4- Open SOFiPLUS for model creation
5- Create a new cross section in the “Cross Section Editor”
6- Create structural lines
7- Create support conditions
8- Create tendons
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Example – Precast Pre-tensioned Beam
2016 / 22 Prestress
k
Workflow: Special considerations
Draw a structural line with group 10 and the defined t-beam as an eccentric cross
section.
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2016 / 23 Prestress
k
Workflow: Special considerations
1- Open new project
2- Define required materials
3- Define the prestressing system
4- Open SOFiPLUS for model creation
5- Create a new cross section in the “Cross Section Editor”
6- Create structural lines
7- Create support conditions
8- Create tendons
Example – Precast Pre-tensioned Beam
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Example – Precast Pre-tensioned Beam
2016 / 24 Prestress
k
Workflow: Special considerations
To create the support conditions, define a rigid link from the insertion point of the
structural line, to the actual support point at the bottom of the beam. Define structural
points with spring elements within group 10.
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2016 / 25 Prestress
k
Workflow: Special considerations
1- Open new project
2- Define required materials
3- Define the prestressing system
4- Open SOFiPLUS for model creation
5- Create a new cross section in the “Cross Section Editor”
6- Create structural lines
7- Create support conditions
8- Create tendons
Example – Precast Pre-tensioned Beam
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Example – Precast Pre-tensioned Beam
2016 / 26 Prestress
k
Workflow: Special considerations
In SOFiPLUS, any AutoCAD line can be converted into a tendon. Furthermore, already
created tendons can be copied as often as wanted.
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Example – Precast Pre-tensioned Beam
2016 / 27 Prestress
k
Workflow: Special considerations
In the tendon properties wizard, set the
prestressing load case to 11 and choose
the prestressing system. It is important to
set the Stage No. of Stressing and the
Stage No. of Grouting to 11. This way, the
tendon will always be bonded to the
concrete. Select the method to “According
Stresses”. For the jacking procedure,
select “Tensioning”.
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Example – Precast Pre-tensioned Beam
2016 / 28 Prestress
k
Workflow: Special considerations
Change the default option Enable
additional data from no to yes, and
choose the force transition length
(no anchor) to e.g. 2.0 m.
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2016 / 29 Prestress
k
Workflow: Special considerations
9- Define and assign loads
10- Export model to SSD
11- Control the prestressing forces and immediate losses
12- Define the construction stages with task CSM
13- Calculate other required tasks
14- Control results
Example – Precast Pre-tensioned Beam
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Example – Precast Pre-tensioned Beam
2016 / 30 Prestress
k
Workflow: Special considerations
If immediate losses due to elastic shortening are to be considered, please take them into
consideration by using a factor while defining the prestressing system or when performing
the design combinations.
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2016 / 31 Prestress
k
Workflow: Special considerations
9- Define and assign loads
10- Export model to SSD
11- Control the prestressing forces and immediate losses
12- Define the construction stages with task CSM
13- Calculate other required tasks
14- Control results
Example – Precast Pre-tensioned Beam
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Example – Precast Pre-tensioned Beam
2016 / 32 Prestress
k
Workflow: Special considerations
Choose the following Stages definition and Groups definition. The superimposed dead loads
and long term creep effects will act on the composite cross section. All other loads will act
on the precast section.
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Example – Precast Pre-tensioned Beam
2016 / 33 Prestress
Workflow: Special considerations
In reality CS10 and 11 happen at the same time, meaning that when the prestressing
tendons are cut and force is transferred to the cross section, a camber will occur. At this
same moment, the beam self-weight will create a deformation in opposite direction until an
equilibrium is reached
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2016 / 34 Prestress
k
Workflow: Special considerations
9- Define and assign loads
10- Export model to SSD
11- Control the prestressing forces and immediate losses
12- Define the construction stages with task CSM
13- Calculate other required tasks
14- Control results
Example – Precast Pre-tensioned Beam
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Example – Precast Pre-tensioned Beam
2016 / 35 Prestress
Workflow: Special considerations
Check results: Animator, Result Viewer, Wingraf
LC 4000 Accumulated forces from the construction stage calculation
LC 5000 Individual results from the construction stage calculation (differences)
LC 6000 Creep and shrinkage results
LC 7000 General stress results
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Example – Precast Pre-tensioned Beam
2016 / 36 Prestress
Workflow: Special considerations
LC 4010: Activation of precast segment
(no loads applied yet!)
LC 4011: Prestressing + segment self weight;
deformed geometry
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Example – Precast Pre-tensioned Beam
2016 / 37 Prestress
Workflow: Special considerations
LC 4020: Self weight of wet concrete LC 4040: Hardening of in situ concrete
(no change in stresses!)
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Example – Precast Pre-tensioned Beam
2016 / 38 Prestress
Workflow: Special considerations
LC 7011: Prestressing + activation of precast segment self weight ; stress distribution on
the cross sections
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Example – Precast Pre-tensioned Beam
2016 / 39 Prestress
Workflow: Special considerations
LC 5011: Forces along the beam (Nx, My)
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Example – Precast Pre-tensioned Beam
2016 / 40 Prestress
Workflow: Special considerations
LC 6015: Long term prestressing losses along the beam (Nx, My)