Prestressed Concrete

Prestressed septic tank with 3D tendon guide
Prestressed septic tank with 3D tendon guide

The Prestressed Concrete module was developed for all applications of prestressing with subsequent bond or without bond, which means it is particularly well suited for calculating prestressed concrete bridges, containers and floor slabs. The module is based on a 3D tendon guide that can be used for all beam, shell and solid models. The functions are divided into tendon group input, load processing in the FEM analysis section and checks according to EN 1992-1-1, EN 1992-2, DIN 1045-1, DIN Technical Report, OENORM and SIA.

Prestressing of Beam, Shell and Solid Structures:

  • Element-independent 3D tendon group guide
  • Cubical spline function
  • Tendon group editing on the system and in any section
  • Consideration of friction, unintentional deviation and slippage
  • Observance of allowance coefficient κ
  • Display of the prestressing force curve and the tendon group radii
  • Identification of system reactions resulting from prestressing
  • Calculation of creep and shrinkage coefficients
  • Creep and shrinkage with tendon group redistributions
  • Design and checks according to EN 1992-1-1 and EN 1992-2 with the national annexes, DIN 1045-1, DIN-Technical Report and SIA.

Actions from Prestressing

Tendon groups are entered interactively on the existing structure model. These groups are defined independent of elements, which allows them to take any course through the structure and be freely copied or moved.For designing the tendon group geometry, a variety of help options are available, such as longitudinal or section view for editing. This makes it possible to directly evaluate the prestressing curve with regard to straining, weakening, slippage and friction. The maximum permitted prestressing force is determined using the k allowance value.

The forces arising from the tendon group geometry and the prestressing force curve are then applied to the system. Afterwards the calculated internal forces, deformation and other factors are available for additional checks.

Creep and Shrinkage

The program determines concrete creep and shrinkage based on a time-dependent stress-strain law developed by Trost. The prestressing steel single layers are included in the calculation of the creep and shrinkage load case while the entire rigidity matrix is being processed. This results in composite elements whose strain state is taken to determine the corresponding share of internal forces of the composite components.

This approach is implemented for all element types. Creep redistribution can therefore also be determined for area and solid models. The necessary creep and shrinkage coefficients can optionally be calculated.

Prestressed Concrete Checks

The checks can be used for all engineering constructions according to the specifications of the Eurocode EN 1992-1. Various components can be combined within the structure model:

  • non-prestressed components
  • prestressed components with subsequent bond
  • prestressed components without bond
  • components with external prestressing
  • mixed construction components

In addition to the checks described in the reinforced concrete section above, the fatigue of the tendons and their allowed stresses as well as the decompression are checked as a result of prestressing. These checks use additional rules for prestressed components such as the inclusion of variation coefficients for the effect from inner prestressing in the construction and final states as well as the bond coefficient ξ.