﻿ Non-linear elastic soil iteration control [SOILCTL]

# Non-linear elastic soil iteration control [SOILCTL]

Specification of non-linear elastic soil iteration control parameters (Input Table)

Table description:

Through the input data table SOILCTL the soil iteration process is given boundary conditions.

As a principle the calculation process will continue until for each node of the pipeline the soil-reaction/relative pipe-displacement fulfils the soil characteristics at that node and specified in Design Function 3.

By means of the parameter MAXSIT the number of soil iterations to be performed is given a maximum. In case the process fulfils the criteria with less iterations the process will stop then in case of geometrically LINEAR calculations. For geometrically NON-LINEAR calculations see table GEOMCTL. If at a number of consecutive nodes one of the soil criteria is not yet met the string containing these nodes is called an ERROR-FIELD. The soil iteration criteria are scanned one after the other and each time a node may add to an error-field of that criterion. Through the parameter MERPTS the maximum number of error points that is allowed in an error-field is specified. Iteration goes on for any error field containing more than the maximum number of error points. Iteration goes on as well if the sum of all error fields exceeds MERFLDS.

At an early design stage it will not be necessary to execute the iteration process completely. In that case a number of error fields each containing a number of error points, can be allowed. As soon as no error-field contains more than the allowed number of error points and the total number of error-fields does not exceed MERFLDS, the iteration process will stop (in case of geometrically LINEAR calculations).

The lowest number of iterations defined through MAXSIT, MERPTS or MERFLDS is decisive for the soil iteration process.

In case the design does not contain soil the table is not used.

The boundary nodes are contained in the soil control model described here as well. These nodes must behave linearly to fulfil the stiffness matrix conditions. Separate warning messages are given during performance of the function if this condition is not fulfilled.