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Bridging Your Innovations to Realities
Date: February 23rd , 2012
Topic: Construction Stage Analysis
Presenter: HyeYeon Lee
midas Civil Advanced Webinar
2
Introduction
Modeling Features
Construction Stage Analysis Control
Results
Contents:
Bridging Your Innovations to Realities
1. Introduction
midas Civil Construction Stage Analysis
Need of Construction Stage Analysis:
Construction Sequence may lead to critical force effects which may lead to shear or flexural failure
Long Unsupported cantilever sections may induce forces which may be substantially different
from those in completed structure:
Time Dependent material properties also play a major role in segmental bridge construction
Negative Moments
Construction Stage
Final Bridge Profile – Continuous Structure – Lesser Negative Moments at Mid Supports
Bridging Your Innovations to Realities Construction Stage Analysis
Modeling of Structure
Defining Structure Groups
Defining Loads under Load Group
Defining Boundary under Boundary Groups
Generation of Construction Stages
Defining Construction Stage Data
Construction Stage Analysis Control
1. Introduction
midas Civil
Flow Chart of Construction Stage Analysis:
Bridging Your Innovations to Realities Construction Stage Analysis
1. Introduction – Construction Stage Definition
midas Civil
Bridging Your Innovations to Realities Construction Stage Analysis – Modeling Features midas Civil
1. Importance of Defining Groups
Groups
Structure Boundary Load
Groups are important because:
Only the structure groups, load groups or boundary groups can be activated or deactivated
in the construction stages, element number or load case name cannot be used to deactivate.
Tendon group is not used to activate or deactivate a tendon, it is just used to see the results
of a certain number of tendons together.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
MODEL
Spliced Girder Bridge
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Model
Stage 1
Stage 1:
Construction of Concrete Box Girder
Temporary supports are provided as shown
Concrete Box Girder will be modeled as
a grillage model
Self Weight of the Girder and Piers will be
activated
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Model
Stage 2
Stage 2:
Construction of Prestressed Beams
Prestressed Girders will be simply supported
via temporary supports
Beam End release will be used to simulate the
simply supported nature
Activation of end supports
Self weight and prestressing will be considered
Deck will be casted on day 10, so the weight of
scaffolding and wet concrete will be activated
on day 10
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
Stage 3
Stage 3:
Deck will be activated by activating part 2 of
the composite section.
Scaffolding weight and wet concrete weight will
be removed.
Temporary Supports will be removed
Post – Tensioning will be done
Bridging Your Innovations to Realities Construction Stage Analysis – Modeling Features midas Civil
1. Element Activation/Deactivation
Activate those elements which will become structural components in a Construction Stage
The elements which still have scaffolding or wet concrete should be included as weight as
they would not contribute in the stiffness of the structure.
Precast girder lifting Cast in-situ balanced cantilever
Bridging Your Innovations to Realities Construction Stage Analysis – Modeling Features midas Civil
1. Element Activation/Deactivation
Elements 17 and 25 have to be activated in CS3
Step 1: Elements Modeled
Step 2: Assign Structural Groups to Elements
Drag and Drop
Step 3: Structure Group Activated in CS3
Bridging Your Innovations to Realities Construction Stage Analysis – Modeling Features midas Civil
1. Element Activation/Deactivation
Define age of
the element
at the time of
activation,
used in
determining the
time dependent
material
properties
Define the
percentage of
the forces
resisted by the
element to be
deactivated
that needs to be
distributed
to other elements
CS 2
Casting
of Deck
CS 3
Scaffolding
Removed
0 30 40
CS 1
60
Age = 21 days
Bridging Your Innovations to Realities Construction Stage Analysis – Modeling Features midas Civil
1. Element Activation/Deactivation
How to Model an Element which has been casted but the scaffolding will be removed in the next stage
1. Elements Load must be activated in the construction stage in which it is casted by nodal loads or
moments if needed.
2. When the scaffolding is removed, nodal load defined in 1 must be deactivated and element must be
activated. The self weight function will now automatically consider the weight of the element.
3. Self Weight must be activated at day 1 of the 1st constructions stage
Scaffolding Scaffolding
CS 8 – Elements casted
on day 7
CS 9
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
1. Element Activation/Deactivation
CS 8 : Activating the wet concrete and
scaffolding weight on day 7 CS 9 : Activating the Element
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
1. Element Activation/Deactivation
CS 9 : Deactivating the load
Bridging Your Innovations to Realities Construction Stage Analysis midas Civil
2. Composite Section Activation/Deactivation
How to define the composite section for construction stages?
The stage in which the section becomes composite can be defined in:
Load -> Construction Stage Analysis Data -> Composite Section for Construction Stage
Bridging Your Innovations to Realities Construction Stage Analysis midas Civil
3. Boundary Activation/Deactivation
Activate the support/boundary which becomes active in a certain construction stage
Deactivate the temporary support
Bridging Your Innovations to Realities Construction Stage Analysis midas Civil
3. Boundary Activation/Deactivation
Step 1: Define Boundary Groups
Step 2: Assign boundary groups to supports
Step 3: Activate Supports
Bridging Your Innovations to Realities Construction Stage Analysis – Modeling Features midas Civil
3. Boundary Activation/Deactivation
Original: Apply the
boundary condition to the
un-deformed position. This
is equivalent to imposing
forced displacements to the
original position prior to
providing the supports.
Deformed: Apply the
boundary condition to the
deformed position
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
3. Boundary Activation/Deactivation
Original and Deformed option
Original option Deformed Option
This is equivalent to imposing forced
displacements to the original position prior
to providing the supports.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
3. Boundary Activation/Deactivation
Original and Deformed option
Original option is used when the structure will be lifted to a desired support location
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
3. Boundary Activation/Deactivation
Beam End Release: Useful to simulate the Non Continuous nature of girder before the deck is casted.
Simple Girder
2 span continuous girder
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
4. Load Activation/Deactivation
Step 1: Define Load Groups
Step 2: Assign Load Groups to load cases
Step 3: Activate Loads
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
5. Tendon Activation/Deactivation
Tendon Activation
Tendons are activated as loads
1. Define the tendon prestress load under a load group.
2. Activate the load group when the tendon is installed or prestressed
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
6. Construction Stage Load Type
Construction Stage type load case is only applied to the constructions stages.
Static load cases are applied to constructions stages as well as Post CS mode.
If self weight is defined as Construction Stage load type, the force effect will be
accumulated through all the stages
If the self weight is defined as Dead Load, the self weight is applied to the final structure for
obtaining force effects in Post CS.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
7. Creep And Shrinkage
Procedure:
1. Define Creep and Shrinkage Properties – Model -> Properties -> Time Dependent
Material(Creep/Shrinkage)
2. Link the property so defined with material using Model -> Properties -> Time
Dependent Material Link
Model -> Properties -> Time
Dependent Material(Creep/Shrinkage)
Model -> Properties -> Time Dependent Material Link
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
7. Creep And Shrinkage
Creep and Shrinkage Function can be defined by the user.
Model -> Properties -> Time Dependent Material ( Creep & Shrinkage )
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
7. Creep And Shrinkage
Creep Coefficient can also be defined in
Construction Stage Loads -> Creep Coefficient for construction stage
A Creep coefficient is directly entered in a form of load, which is necessary to provide freedom to user-specify
the desired creep coefficients for specific members.
The entered creep coefficient by this feature overrides the creep coefficient defined by the creep function.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
7. Creep And Shrinkage
Application of Creep and Shrinkage:
Creep and Shrinkage coefficients for the elements are taken as per the age of the activation
of the element in the construction stage definition.
Creep coefficients and shrinkage values can be seen either in :
1. Results -> Results Table -> Construction Stage -> Element Properties at each stage
2. Out File Generated : Results -> Text Output
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
7. Creep And Shrinkage
Notational Size of the Member:
Notational Size = 2*Ac/u ( Ac = Sectional Area , u = perimeter in contact with atmosphere.
1. Beam Elements: Notational Size can be defined while defining the time dependent
material property for creep and shrinkage or by Changing the Time Dependent material
parameters.
Time dependent material property for creep and shrinkage
Changing the Time Dependent material parameters
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
7. Creep And Shrinkage
1. Beam Elements ( Composite Sections ): Individual notational size can be defined for
girder and deck in Composite Section for Construction stage dialogue box
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
7. Creep And Shrinkage
1. Plate/Solid Elements: Notational Size can be entered either while defining time
dependent material property for creep/shrinkage or by Change Element Dependent
Material Property.
Automatic Function cannot be used in Change Element Dependent Material Property
for plate and solid Elements.
Definition of Ac and u for Plate and Solid Elements :
Ac : Area of Cross section
u : Perimeter in contact with atmosphere:
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
7. Creep And Shrinkage
Important Consideration for Plate and Solid Elements:
1. Local Direction of the Elements must be aligned.
2. Local x axis of the elements must coincide with the bridge direction
Incorrect
Correct
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
7. Creep And Shrinkage
Construction Stage Loads can be used to define the time lag in the construction of segments.
Segment A constructed 100 days before Segment B
Construction Stages for Segment A and Segment B are same. Hence construction stages can be modeled such
that the elements for segment A and B appear simultaneously.
At the time of Joining of Segment A and Segment B, the time lag can be introduced by applying Time Load for
Construction stage
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
8. Development of Concrete Strength
Define Compressive Strength of concrete or the change of modulus of elasticity to reflect
the variation of modulus of elasticity with time.
Procedure:
1. Define the variation of Compressive strength in Model -> Properties -> Time
Dependent Material Property for Comp Strength
2. Link the variation to the material
Model -> Properties -> Time Dependent Material
Property for Comp Strength Model -> Properties -> Time Dependent Material
Link
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
8. Section Stiffness Scale Factor
Section Stiffness can be changed with construction stages by defining the section stiffness scale
factor in Section Manager.
Section Stiffness factor can be assigned to a section and defined under a boundary group.
Boundary Group can be activated in the construction stage.
For normalizing the section stiffness, another scale factor which normalizes the stiffness must
be activated along with the deactivation of pervious scale factor
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
9. Effective Width Scale Factor
Effective width scale factor can be defined to take into account the effective flange width for the
calculation of sectional stresses.
Effective width scale factor is considered only in determining stresses as against stiffness scale
factor which is used for generating stiffness matrix.
Effective width can be defined in two ways:
1. Automatically – By using the PSC Bridge Wizard
2. Manually – By Model -> Boundaries -> Effective Width Scale Factor
Effective Width scale factors can be assigned to a boundary group and activated at will.
PSC Bridge Wizard Effective Width Scale Factor
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
10. Dummy Stage For Obtaining Results
A Dummy stage having no elements or boundaries activated can be used to get the effect due to a
specific load.
Suppose, at the end of a 150 days of construction having each construction stage of 30 days,
temperature stresses are desired.
We will define a dummy construction stage rite after CS5 (30*5 = 150 days ) and activate the
temperature load in that stage. Thus the under the CS: Dead Load – the effect of temperature load
can be seen.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
1. Final Stage
Final Stage for the analysis can be selected. If the final stage is defined as: CS2, then the analysis
stop at CS2. Stages beyond CS2 are not analyzed.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis Control
2. Restart Construction Stage Analysis
Restart the construction stage analysis from the specified stage.
Restarting the analysis from the modified stage saves time.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
3. Time Dependent Effect
Select which time dependent
effect needs to be analyzed out
of Creep and Shrinkage
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
3. Time Dependent Effect
Select Convergence Criteria
for creep analysis
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
3. Time Dependent Effect
Perform the construction stage
analysis only using the creep
coefficients defined in creep
coefficient for Construction stage
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
3. Time Dependent Effect
Specify a number, which is used to
divide a construction stage to create
internal steps for considering creep.
The steps will only be used for
analysis, results cannot be seen
for those steps
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
3. Time Dependent Effect
Check on to reflect the effect of
prestressing tension loss of tendons
due to creep and shrinkage.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
3. Time Dependent Effect
Check on to reflect the effect
of rebar confinement for creep
and shrinkage.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
3. Time Dependent Effect
Whether or not the time
dependent effect is to be
applied to the POST CS
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
3. Time Dependent Effect
Check on to reflect the prestressing
tension loss of tendons due to the
elastic deformations of concrete due
to loads other than prestress load
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
4. P Delta Analysis Control
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
5. Erection Load
Select the load case which needs to be distinguished from the CS: Dead Load in the Construction Stage Analysis Results
Select the Load Type for the Erection Loads
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
6. Initial Force Control
The member (axial) forces of the last step of the last construction stage in a construction stage analysis are converted into
Initial Force for Geometric Stiffness to reflect the forces into the geometric stiffness of the structure at the post construction
(Post CS) stage.
Useful for Eigen Value Analysis considering geometric stiffness of cables.
When P – Delta Analysis is done this effect is already considered
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
6. Initial Force Control
If both Initial Element Forces table and Initial Element Forces(CS) table are entered, Initial Element Forces
table directly entered by the user will be applied first in priority.
However, if “Apply Initial Member Force to C.S.” is
checked on, (Initial Element Forces(CS)) at the last step of the last construction stage will be applied to the Post CS stage.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
7. Initial Tangent Displacement to Erected Structues
This function calculates real displacements of the elements, which will be created in the next stage, considering
the rotational angles of nodes resulting from each current construction stage.
This functionality is used for fabrication cambers for structural steel and precast concrete members.
In Large Displacement analysis this function is by default considered
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
7. Initial Tangent Displacement to Erected Structures
New Segment
Deflection due to rotation of
node at which it has to be joined to
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
8. Stress Decrease at Lead Length Zone
Select a method of computing stresses over a transfer length in a post-tension model.
This feature is applicable only when a Transfer Length is entered in the Tendon Profile dialog.
If Composite section for Construction Stages is used this function cannot be applied.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
9. Change of Beam Section Properties with Tendons
Select whether to consider the presence of tendons for calculating section properties.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
10. Save Output for Current Stage/Step
Save Results for Current Stage
Results for Current Step can be seen by selecting Current Step Force
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Modeling Features
11. Options for Saving Results
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
1. Construction Stages Results
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
2. Deformation – Accumulated Deformation
The default results obtained for Construction Stage analysis are
accumulated results i.e. if we check the deformation due to dead load
for CS 2, if would be the deformation for CS1 + the deformation
obtained due to dead load in CS2.
Current Step deformations are obtained by applying the current step force
to the structure.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
2. Deformation – Current Stage Displacement
Current Stage Displacement gives the deformations obtained by
applying the current step force ( activated in that step) to the structure.
Accumulated Deformation at CS10 = Accumulated Deformation at CS9
+ Current Stage Deformation CS10
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
2. Deformation – Stage/Step Real Deformation
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
3. Beam Diagrams – Accumulated
The default results obtained for Construction Stage analysis are
accumulated results i.e. if we check the bending moment due to
dead load for CS 2, if would be the bending moment for CS1 + the
bending moment obtained due to dead load in CS2.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
3. Beam Diagrams – Current Step
Current Stage Beam Diagram gives the Diagram obtained by
applying the current step force ( activated in that step) to the structure.
Accumulated Bending Moment at CS10 = Accumulated Bending Moment at CS9
+ Current Stage Bending Moment at CS10
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
4. Stresses
Stresses can be checked for individual steps of Construction stages.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
4. Stresses – Part 1 and Part 2
Individual stresses can be obtained for different parts of Composite
section.
The option becomes activated when the Composite section for
Construction stages is activated.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
5. Tendon Time Dependent Loss Graph
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
5. Tendon Time Dependent Loss Graph
Loss Pre- Tensioned Post - Tensioned
Friction Loss
Anchorage Slip Loss
Elastic Shortening Loss
Creep/Shrinkage Loss
Relaxation Loss
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
6. Tendon Time Dependent Loss Table
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
6. Tendon Loss Table
Stress in the tendon after instantaneous loss.
Post – Tensioned Beams:
Instantaneous loss includes :
Friction Loss
Anchorage Loss
** Elastic Shortening loss is considered to have taken place
already during prestressing
Pre – Tensioned Beams :
Elastic Shortening Loss only due to prestressing ( not due to
self weight)
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
6. Tendon Loss Table
Anchorage Loss
Where: p is the frictional resistance per unit length determined the friction loss between the
anchorage and quarter length of the beam and dividing it by L/4
Friction Loss:
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
6. Tendon Loss Table
Other types of elastic shortening losses, which are caused by subsequent loadings
(self weight, live loads, creep, shrinkage, etc.) after the prestressing force is applied, are
included.
Elastic Shortening due to prestressing of other tendons is included:
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
6. Tendon Loss Table
Tendon Loss due to creep and Shrinkage
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
6. Tendon Loss Table
Tendon Loss due to Relaxation of Tendon
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
7. Stage/Step History Graph
Plot history graphs by steps and stages or load cases/combinations using the analysis
results of a structural model, which is analyzed for construction stages and steps that
typically form the basis for a geometric nonlinear analysis or construction stage
analysis.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
8. Element Properties at Each Stage
Check the element properties at each construction stage (start age, end age, modulus
of elasticity at the start, modulus of elasticity at the end, cumulative shrinkage and
cumulated creep coefficient) in a spreadsheet format table.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
9. Activation/Deactivation Status Table
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
10. Base Stages, Min/Max, Post CS
Base Stage: All the modeling is done in the base stage.
Min/Max: The minimum ( most negative ) and the maximum ( most positive) force effects
from the constructions stages.
Post CS: The structure obtained at the last stage at which the moving load analysis, dynamic
analysis is performed.
Bridging Your Innovations to Realities midas Civil Construction Stage Analysis – Results
11. Load Combinations
Thanks