FAQ 004623 | How can I incrementally apply the load of a load case to the model?

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First Steps with RFEM

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We provide hints and tips to help you get started with the basic program RFEM.

08/12/2020

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Andreas Niemeier

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Question

How can I incrementally apply the load of a load case to the model?

Answer

In the calculation parameters of RFEM or RSTAB, there are the "Number of load increments for load cases/load combinations" text boxes under the "Global Calculation Parameters" tab. These two entries control the numerical incremental application of the defined load boundary conditions in the respective load cases and load combinations. The reciprocal value of the entry describes a fraction of the load. The solving process then applies the defined load fractions successively to the model in so-called load increments until the complete load is reached. In the respective load increments, the equation solver tries to find an equilibrium within the maximum allowed iterations, and thus to specify suitable start values for the next load increment.

Figure 02 - Calculation Parameters

It is possible to imagine that the solving process collects the complete load of a load case or a load combination in a "watering can" and pours it onto the load-collecting model in portions. In this case, the number of load increments correlates with the speed of the load application. The speed is not to be understood as a real time parameter, but purely numerically.

Figure 01 - Deformation Development Dependent on Load Increment

The incremental load application has only an effect in the case of nonlinear structural systems. It usually provides a correspondingly higher result quality with increasing number of load increments. The basic aim of this method is to find a micro convergence in the respective load increments to specify new high-quality start values for the next load increment, and thus finally to achieve a macro convergence for the entire load case.

Figure 03 - Calculation Diagrams

Keywords

Dlubal FAQ Increments Nonlinearity Convergence Solver Iteration Watering can Frequently Asked Question FAQ about Dlubal Question and Answer about Dlubal

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  • Updated 09/10/2020

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