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jahnavi

random response analysis

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hi sir,

 these are different load collectoes defined in random response analysis tutorial they have explained about randps and tabrnd1 can u please  tell what values are defined in other load collectors and they used two load steps(load1 and load 2) can u pls explain about that also??

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@jahnavi

 

RANDOM takes RANDPS. RANDPS takes loads (excited load and applied load... FRF) and TABRND1 which refer to power spectral data.

 

 

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they have defined total of 10 load collectors FREQ156, R , Rload2 , TABLE , SPC , force , FREQ 257 , DAREA2  what  did they define in these load collectors ? why do we need force when we are defining psd??

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Jahnavi,

 

There are number of loadcollectors to define multiple loads.  Load can be in any form, like velocity, load, acceleration etc...

 

The total PSD will be a sum of PSD responses of individual loads. These loads can be same or different.

 

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hi sir ,

In my problem i don't want to constraint my model, i want to give psd at some nodes allowing them single dof i.e base excitation

i have doubts at each step can u pls clarify them

my input is only acceleration psd or displacement psd over a range of frequencies

 

1. I will give only SPCD not spcs. in spcd what is that displacement mean? i want to change the displacements over a range on frequencies i.e psd.how can we give acclerations in spcd instead of displacement?

2. then a tabrnd1 is created. after that randps is created. what should be specified in J?? is that spcd??

3. what is the difference in acceleration given at spcd and tabrnd1??

 

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Jahnavi,

 

Displacement means enforcing the node to displace by a certain magnitude. In RLOAD you can change to Acceleration.

 

Since you have only one load specify the same for both J and K

 

If you have given a value of 5 in SPCD for instance, it will be used as a factor in tabrnd1.

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