• Registered: 14-04-2010
  • Posts: 7

Topic: gravitational loading (DeadWeight) question

Hi Borek,

If I want a gravitational force to act in the negative y-direction, does that mean that the acceleration component in the DeadWeight declaration should be positive (as in other codes) or negative?  I'm a little confused given the DeadWeight class definition that says the acceleration components are expected to be downwards vertical.

Can you clarify the sign convention for me?  In searching through other posts I've seen what looks like gravitational loading values specified both positive and negative.

Thanks in advance.

2 Reply by bp

  • bp
  • Administrator
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  • From: Prague, Czech Rep.
  • Registered: 02-03-2007
  • Posts: 1,033

Re: gravitational loading (DeadWeight) question

Hi Chris,

the DeadWeight class can be used to apply any constant body load. The component values determine the intensities per unit volume acting in direction of individual degrees of freedom (this is resolved at the element subjected to given load). The intensities are multiplied by material density and integrated over the element volume - do not forget to specify real material density. So you can specify gravitational force acting in negative y direction simply like this (3d problem assumed):

Lspace 1 nodes 8 1 2 3 4 5 6 7 8 mat 1 crosssect 1 bodyLoads 1 2
...
isole 1 E 30e3 nu 0.2 d 2.5
...
DeadWeight 2 loadTimeFunction 1 valType 2 components 3 0.0 -9.81 0.0

Borek

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  • Registered: 14-04-2010
  • Posts: 7

Re: gravitational loading (DeadWeight) question

Thanks Borek!  That's clear now.

Chris