Users:Form Finding/Form Finding with CARAT++

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	MUE_RELAX=0.0		MUE_RELAX=0.0
	</pre>		</pre>
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		+	=== Benchmark examples ===
		+	* form-finding of a four-point sail: ..\examples\benchmark_examples\analyses\formfinding_membrane1_I\cbm_4_point_Fofi.txt
	== References ==		== References ==
	<references/>		<references/>

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Revision as of 08:25, 13 January 2017

The following table shows the important commands to define a form finding analysis in CARAT++ and gives an explanation for each parameter.

Compulsory Parameters
Parameter	Values	Description
PC-ANALYSIS	int	Analysis with the number int the number have to be followed by : FORMFINDING
DOMAIN	EL-DOMAIN int	Domain which should be calculated. The parameter EL-DOMAIN should be defined in the Element Block of the Inputfile
OUTPUT	PC-OUT int	Definition of the Output object. The Parameter PC-OUT should be defined in the PC-Problem Block of the Inputfile
SOLVER	PC-SOLVER int	Definition of the Solver object. The Parameter PC-SOLVER should be defined in the PC-Problem Block of the Inputfile
COMPCASE	LD-COM int	Definition of the Computation Case. The Parameter LD-COM should defined in the Load-Block of the Inputfile
FORMFINDING_STEP	int	Definition of the number of form finding steps
MAX_ITER_EQUILIBRIUM	int	Maximum of number of equilibrium iterations before CARAT++ stops the calculation
EQUILIBRIUM_ACCURACY	real	Equilibrium accuracy
FORMFINDING_ELEMENTS	PROP_ID ints	elements that have to be formfound (i.e. that have no material contribution, but only geometrical stiffness), identified through their property ID
Optional parameters for full URS
HOMOTOPY_CURVE	LD-CURVE int	Defines the homotopy factor (has to be between 0 and 1) for the different form-finding steps in a separate curve. If not used, the homotopy factor is set to 0, i.e. the reference problem is solved.
Optional parameters for stress adaption / distortion control
STRESS_ADAPTION	PROP_ID ints	Defines for which elements the distortion control is active through their property ID
LAMBDA_MAX	real	Maximum allowable element distortion in case of stress adaption
MUE_RELAX	real	Relaxation of the element distortion (Values between 0 and 1 are valid)

For the better understanding of the syntax of this kind of analysis in the following an example of an input block for a form finding will be shown.

Example of an Input Block

The input block shown below defines a formfinding analysis with the IDs 1,2 and 8. The analysis performs 10 formfinding steps and stops the computation after 100 equilibrium iteration steps within each formfinding step if no convergence is achieved. The equilibrium accuracy of the analysis is defined as 10^-6.

The (optional) distortion control is enabled and used for elements releated to the elemnt properties with ID 1. The maximum allowed element distortion is 1.1 and the relaxation of the element distortion control is set to 0. For a detailed discussion of the element distortion control see e.g. to ^[1] and ^[2].

PC-ANALYSIS 1: FORMFINDING
  DOMAIN = EL-DOMAIN 1
  OUTPUT = PC-OUT 1
  SOLVER = PC-SOLVER 1
  COMPCASE = LD-COM 1
  FORMFINDING_STEP = 10
  MAX_ITER_EQUILIBRIUM = 100
  EQUILIBRIUM_ACCURACY = 1e-06
  FORMFINDING_ELEMENTS = PROP_ID 1,2,8
  STRESS_ADAPTION = PROP_ID 1
  LAMBDA_MAX=1.1
  MUE_RELAX=0.0

Benchmark examples

• form-finding of a four-point sail: ..\examples\benchmark_examples\analyses\formfinding_membrane1_I\cbm_4_point_Fofi.txt

References

1. ↑ Linhard, J.: Numerisch-mechanische Betrachtung des Entwurfsprozesses von Membrantragwerken, Lehrstuhl für Statik, Technische Universität München, 2009
2. ↑ Dieringer, F.: Numerical Methods for the Design and Analysis of Tensile Structures, Lehrstuhl für Statik, Technische Universität München, 2014

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