Setting arc length

The arc length is the basic parameter affecting the response calculation. An indicator for the selection of arc length can be the course of iteration in the previous solution stage. Regardless of that the program enables the following setting:

Determine from load step – the arc length is determined automatically from the initial load step.

Assign from the previous stage – the value of arc length at the end of the previous calculation stage is used as a starting value for a new stage. This option becomes active in the second stage of construction.

Input – the value of arc length can be directly prescribed.

Providing the structure response cannot be determined prior we recommend using the first option. Depending on the course of calculation it is possible to adjust the value of arc length and repeat the calculation. At no event, however, is it possible to ensure convergence for an arbitrary value of arc length selected. Similarly to NRM, if the convergence problems occur the program allows for the reduction of the current arc length and restarts the calculation.

The next parameter driving the iteration process is the Maximum No. of load steps. The program always carries on the prescribed number of load steps providing:

- parameter λ exceeds 1,

- the maximum number of relaxations of arc length is exceeded.

Providing the analysis is terminated due to exceeding the maximum number of prescribed load steps and parameter λ is less than 1, it is necessary to increase the number of steps and restart the analysis.

Arc-length – arc length setting