Construction Stages, Creep Redistribution
The steps to create and handle construction stages is described below.
Using a simple example, the calculation of creep redistribution as a result of a system change is then explained with the help of construction stages.
Construction stages can be calculated for any structure. For every construction stage a file is created for which all calculation options are available. The systems and their properties are 'inherited' from one construction stage to the next. Redundant use of load cases and elements is prevented by the system. The results of the individual construction stages can be combined with or superposed over one another.
The following steps are taken to create construction stages:
First fully enter the original system for the first construction stage. The file name must end with (1), for instance Bridge(1).FEM.
In the file menu the function Construction stage... is now active. In order to create the second construction stage, choose this function and click New... The second construction stage (here: Bridge(2).fem) is automatically generated and activated. System changes or expansions can now be introduced. The results from the previous construction stages are available for load case combination or superpositions.
Using this method, you can create any number of additional construction stages. The function Construction stage... can be used to switch between the individual construction statuses by double-clicking.
The original system, construction stage 1, consists of 2 single-span beams with a length of 4.00 m and 6.00 m. Material: C20/25, Section: T-beam.
For the original system the following is calculated:
Load case 1: Dead load
Load case 2: Creep t=10 to t=50 days, with phi.t = 0.66, creep-generated continuous load LC 1
Now the construction stage 2 is generated and the system changes are implemented here. By removing the joint, a continuous model is created. The additional load is placed on top of it and calculated:
Load case 3: Additional load 10 kN/m
The internal forces and deformations after 50 days result from the dead load + creep 10/50 + the additional load:
Load case 4: Superposition LC 1, 2 and 3 (superposition of the results)
The creep redistribution up to the final state is calculated by:
Load case 5: creep 1=50 to final state, phi.t=2.04, creep-generated continuous load: LC 4
The final state results from load case 4 and 5:
Load case 6: final state (superposition LC4+LC5)