Internal forces for 1D member design
SCIA Engineer offers 2 options how and where to display internal forces on concrete members: one in the Results workstation and one in the Concrete workstation. This FAQ explains the difference between them.
Internal forces from FEM database
There are 'clean' internal forces from FEM analysis. They aren’t adjusted and you can display them independently on the material. You can find them in via Main menu > Results > 1D members > Internal forces:
Internal forces in concrete service
In the concrete service you can display internal forces via Main menu > Design > Concrete 1D > Internal forces for design.
The result of the internal forces inside the concrete service includes modifications in the design values:
- reduction of forces over the supports of shear and bending
- shifting of bending moment
- influence of first and second order eccentricity.
These internal forces are used for the reinforcement design. The software iteratively recalculates the internal forces with the actual designed reinforcement, so in last iteration step the internal forces are basically recalculated with this (real) level of reinforcement. So in other words, when you run the command for internal forces for design, the whole design is running to get the reinforcement and then get final internal forces.
Note: in older SCIA-versions a parameter 'Estimation ratio of longitudinal reinforcement for recalculation internal forces in design of reinforcement' was used for this, but the new iterative method is more accurate now.
Internal forces in the concrete service can be adjusted by reduction of shear force or moments above supports. These options are off by default and you can turn them on via Main menu > Design > Concrete settings > Settings directly:
All that has some impact on the final reinforcement amount and it can help reducing the project cost.
For concrete checks of 1D members the final reinforcement is used. You can display Internal forces for checks via Main menu > Design > Concrete 1D > Internal forces for checks, but since with the iterative procedure the final reinforcement is obtained these forces should be the same as for Internal forces for design.
Note: you can compare the differences between the original and the recalculated internal forces in the concrete service.
You can call the command of internal forces under the concrete service and select the value of M-MEd or V-VEd. If the option of the reduction is activated (inside the concrete setting), then you will be able to see the difference graphically and numerically: