DOPTPRM, APPROX

Bulk Data Entry Switch to select the approximation type for stress/strain responses of shells, composites and 1D elements.

Definitions

Parameter	Values	Description
`APPROX`	Static Optimization <FULL, REDUCED> Dynamic Optimization <FULL, HIGH, MEDIUM, LOW> Default = FULL (except for Random Response Fatigue Optimization, where default is LOW).	For Static Optimization, available options for response approximation are REDUCED and FULL (these options are applicable for any force-based responses for shells, composites and 1D elements. For example, stress/strain responses): FULL There is no reduction in quality of response approximation. For some large models, it may lead to error 832 (Optimization problem is too large to be solved by OptiStruct). REDUCED All force-based responses will use the constant force approximation method. This method has the benefit of reducing the memory requirement for large optimization problems (for example, many stress/strain responses for many size design variables). Another benefit is the reduction in runtime if the bottleneck occurs due to sensitivity analysis. It is encouraged to try the REDUCED option for the large size optimization models. For Frequency Response Optimization and Random Response Fatigue Optimization, available options for response approximation are HIGH, MED, LOW, and FULL (these options are applicable to responses in dynamic optimization which are combinations or functions of values over a range of frequencies. 1): FULL There is no reduction in quality of response approximation. For some large models, it may lead to error 832 (Optimization problem is too large to be solved by OptiStruct). HIGH High quality MEDIUM Medium quality LOW Low quality This framework allows response approximation (constant response approximation) non-peak responses across a frequency range. Lower quality implies lower memory/computational requirements, while higher quality implies higher run times and memory usage compared to the other options.

Parameter

Values

Description

APPROX

Static Optimization

<FULL, REDUCED>

Dynamic Optimization

<FULL, HIGH, MEDIUM, LOW>

Default = FULL (except for Random Response Fatigue Optimization, where default is LOW).

For Static Optimization, available options for response approximation are REDUCED and FULL (these options are applicable for any force-based responses for shells, composites and 1D elements. For example, stress/strain responses):

FULL: There is no reduction in quality of response approximation. For some large models, it may lead to error 832 (Optimization problem is too large to be solved by OptiStruct).
REDUCED: All force-based responses will use the constant force approximation method. This method has the benefit of reducing the memory requirement for large optimization problems (for example, many stress/strain responses for many size design variables). Another benefit is the reduction in runtime if the bottleneck occurs due to sensitivity analysis. It is encouraged to try the REDUCED option for the large size optimization models.

For Frequency Response Optimization and Random Response Fatigue Optimization, available options for response approximation are HIGH, MED, LOW, and FULL (these options are applicable to responses in dynamic optimization which are combinations or functions of values over a range of frequencies. 1):

FULL: There is no reduction in quality of response approximation. For some large models, it may lead to error 832 (Optimization problem is too large to be solved by OptiStruct).
HIGH: High quality
MEDIUM: Medium quality
LOW: Low quality

This framework allows response approximation (constant response approximation) non-peak responses across a frequency range. Lower quality implies lower memory/computational requirements, while higher quality implies higher run times and memory usage compared to the other options.

Comments

Approximation for Dynamic Optimization via HIGH, MED, and LOW options is currently supported only for RTYPE=FRPRES, FRDISP, FRVELO, FRACCL, FRERP, DAMAGE, and LIFE response types on DRESP1 entry. For effective usage of these options, multiple frequencies or a frequency range should be available for the frequency-based response and the response should be a function or combination of values over a range of frequencies; for example, if the ATTB field is set to RMS, SUM, and so on. Therefore, for DAMAGE and LIFE responses, these options are only applicable for Random Response Fatigue Optimization.