Construction Stage Analysis Control

Enter the analysis conditions for a Construction Stage analysis. Define the final construction stage and select the analysis features among the features, which reflect the time dependent material properties and geometric nonlinearity. To achieve more accurate results for creep and shrinkage in a long duration construction stage, we may select the option of auto-generating steps.

Time dependent material properties

1. Creep effects of concrete members having different maturities

2. Shrinkage effects of concrete members having different maturities

3. Time dependent compressive strength gain for concrete members

4. Prestressing tendon relaxaton

Expression of Construction Stages

1. Creation (activation) and deletion (deactivation) of members with certain maturities.

2. Loading (activation) and unloading (deactivation) of loads relative to time

3. Change of boundary conditions relative to time

1. Model the structure.

2. Define the time dependent material properties such as creep and shrinkage. The time dependent material properties may be user defined or defined by the standards such as ACI and CEB-FIP. (Time Dependent Material(Creep/Shrinkage), Time Dependent Material(Comp. Strength))

3. Link the defined time dependent material properties to the general material properties through which the change of the concrete member material properties with time are automatically calculated and reflected. (Time Dependent Material Link)

4. Create the construction stages and time steps considering the true sequence of construction. (Define Construction Stage)

5. Define the construction stages using the predefined Element groups, Boundary groups and Load groups. (Define Construction Stage)

6. Specify the desired analysis conditions and carry out the analysis. (Construction Stage Analysis Control, Perform Analysis)

7. Combine the results of the construction stage analysis and that of the completed structure analysis as necessary.

Note
Use Construction Stage Wizard for Building Structure to automatically handle the majority of the tasks pertaining to the steps 4 and 5 above.

Procedure	Menu
1. Define material properties	Model>Properties>Material...
2. Define section properties	Model>Properties>Section...
3. Define groups -Structure groups -Boundary groups -Load groups	Model>Group> ① Define Structure Group... ② Define Boundary Group... ③ Define Load Group...
4. Create elements and assign them to the structure groups	Model>Elements>Create Elements...
5. Define boundary conditions and assign them to the boundary groups	Model>Boundaries>...
6. Enter loads and assign them to the load groups	Load>...
7. Define time dependent material (concrete) -Creep, Shrinkage, Compressive strength	Model>Properties> ① Time Dependent Material (Creep/Shrinkage) ... ② Time Dependent Material (Comp. Strength) ...
8. Assign the time history material data to the material properties (concrete)	Model>Properties>Time Dependent Material Link...
9. Apply the geometric shape dimension of frame elements to calculate creep/shrinkage	Model>Properties>Change Element Dependent Material Property...
10. Construction stage - Specify the duration of the construction stage - Activate or deactivate relevant element (structure) groups - Activate or deactivate relevant boundary groups - Activate or deactivate relevant load groups	Load>Construction Stage Analysis Data>Define Construction Stage...
11. Construction stage analysis option - Considering time dependent effect - Load Cases to be distinguished from Dead Load	Analysis>Construction Stage Analysis Control
12. Perform analysis	Analysis>Perform Analysis...
13. Check analysis results for each construction stage	Results>…
14. Check column shortening	Results>Column Shortening Graph for C.S.

From the Main Menu select Analysis > Construction Stage Analysis Control.

Assign a stage to be considered as the Final Stage of the construction stage analysis.

Other Stage
Assign a stage within the overall construction stages as the final stage.

Check to reflect the change of geometric shapes of the geometric nonlinear analysis in the construction stage analysis. Geometric Nonlinear analysis for Independent Stage Model cannot account for time dependent effects simultaneously. However, with Accumulative Geometric Nonlinear Stage Model in V671, the program not only accounts for time dependent effects but also has an option to select the Pretension Type of cables and calculates tangential displacements while taking Lack of Fit Forces into account.

Geometric nonlinear analysis is carried out independently in models of each construction stage. This option is used for the backward analysis of a suspension bridge considering large displacement.

Geometric nonlinear analysis is carried out with accumulated effects of the models of each construction stage. This option is used for the forward analysis of a cable stayed bridge considering large displacement.

Check to reflect the time dependent material properties such as the change of modulus of elasticity, creep and shrinkage in the construction stage analysis.

If “Include Time Dependent Effect” is checked on in the Analysis Option, enter the following information: Define the material properties related to creep and shrinkage in Time Dependent Material (Creep/Shrinkage).

Specify the convergence requirement for ending the repetitive process in the analysis reflecting creep.

Perform the construction stage analysis only using the creep coefficients entered by the user. Creep coefficients are entered by elements in Creep Coefficient for Construction Stage.

Specify a number, which is used to divide a construction stage to create internal steps for considering creep.

Internal Steps are applied in the process of analysis, and the corresponding analysis results are not produced.

Specify a number, which is used to divide a construction stage to create internal steps when the duration of the construction stage is too long.

Internal Steps are applied in the process of analysis, and the corresponding analysis results are not produced.

Check on to reflect the effect of prestressing tension loss of tendons due to creep and shrinkage. Define the tendon properties of the prestressing loss in "Tendon Property".

Check on to reflect the change of modulus of elasticity related to the change of compressive strength of concrete. The maturity variant property is defined in "Time Dependent Material(Comp. Strength)".

Check on to reflect the prestressing tension loss of tendons due to the elastic deformations of concrete.

Prestressing tension loss in tendons due to elastic deformations is caused by other loadings such as live loads, creep, shrinkage, prestressing other tendons, etc after the prestressing force is applied. Note that it is not the same as the elastic shortening loss, which is one of the instantaneous losses.

If “Include Non-Linear Analysis” is checked on in the Analysis Option, enter the following information:

Maximum Number of Iterations/Load Step
Maximum number of iterations of analysis per Load Step.

Convergence Criteria
Specify the basis on which to assess the convergence. Enter the norm values for Energy (Member force x displacement), displacement and member forces.

Note
The selection of the convergence criteria for repeating or ending the analysis must be based on the condition to reflect the effects of various degrees of freedom. For example, in the case of Displacement Norm, if the displacement resulting from the corresponding analysis step is {D1}, and the total displacement accumulated from each step is {D2}, the Norm is expressed as

. If this value is smaller than the specified value, a convergence is considered to have occurred and the program stops the iterative analysis.

Cable-Pretension Force Control

Add: Add external pretension forces to the pre-existing tension forces of cable elements.

Replace: Replace the pre-existing tension forces of cable elements with applied external pretension forces.

Note
If the initial pretension forces are applied as internal forces, the forces in the cable elements become reduced due to the deformation of the support structure based on its stiffness. If the initial pretension forces are applied as external forces, the forces are treated as external loads to the support structure at the construction stage of pretensioning; hence the forces in the cable elements remain unchanged as the initial pretension forces at the corresponding construction stage.

Load Cases to be distinguished from Dead Load for CS Output

Dead Load is generally the most significant component of all the loads applied to construction stage analysis. The results of all the load cases except for Creep, Shrinkage and Relaxation of Tendons are lumped into CS: Dead Load. Here we can select certain load cases to be distinguished from the Dead Load and produce the results under CS: Erection Load.

Load Type for CS:Erection Load: Specify a load type classified into CS:Erection, which is differently categorized from CS:Dead. This is effective when the Auto Generation function of Combinations is used. If the Auto Generation function is not used, it makes no difference which type will be selected.

: Remove the conditions for a construction stage analysis. The construction stage analysis is not performed in this case.

If the “Calculate Output of Each part” option is selected, the construction stage analysis results of composite sections by each Part will be produced. The analysis result for each Part can be checked in Result >> Result Tables >> Composite Section for C.S..