i am smulating an earthquake on a model and its possible whth two ways , whith prescribed displacement or whith a dynamic surface load at the bottom of the model as shown in the tutorials .
My questions are : 1- What's the difference between the two methods.
2-if choose the second method of the surface load : how can i define the axe and the value of the stress in dynamic surface load ?
Greetings.
Dear El-aifa,
In principle, there is no difference between the two ways of applying your signal. You should consider that in PLAXIS we solve the following basic equation (found in our Scientific manual):
So, whether you apply a displacement or an acceleration or a velocity or a load (out-of-balance force) the same equation is solved.
Concerning the surface load, note that this has to do with the data you have as a signal. Typically you have data for accelerations, therefore, you would use a prescribed displacement to apply the signal.
It is possible to apply a surface load and then the signal will be applied as a shear (and, possibly, also normal) stress time history.
To apply the signal by means of a surface load, you need to select the load feature in the graphic interface, change the dynamic load component and assign a multiplier table. The multiplier can be created via the Selection or Model explorer or under menu Structures > Show dynamic multipliers.
Answer Verified By: El-aifa Ourkia
Thank you for your help greetings