Interfaces elements

Question

Dear support team, 
 
 I need to work out stresses at the interfaces elements in Plaxis 3D. 
 By looking to the Plaxis output (actually I am looking to stresses at the integration points) I see there are three components: one normal and two tangential stresses. With regards to these stresses I have the following questions: 
 
 what is the convention of those stresses? 
 to work out the equivalent force per element, I multiply each stress in each gauss point for the correspondent weight (as per Table 5.2 in the scientific manual), then by multiplying the summation of those weighted stresses for the element area. Could you please confirm whether this is correct? 
 
 Kind regards

Stefanos Papavasileiou · Answer

Dear Vincenzo, 
 To answer each question: 
 1. The sign conversion is explained in our Reference manual. In short, compression is negative and tension is positive. 
 2. That seems about right. The Scientific manual, indeed, contains the relevant information.

Dennis Waterman · Answer

Dear Mustafa, 
 Why should tau_1 be in the vertical direction? One could also draw a horizontal interface, in which case there are only horizontal shear directions.... 
 Tau_1 s the shear stress in the "1" direction and tau_2 is the shear stress in the "2" direction. These directions can be found by showing the local axes for the interface (Options menu -> show local axies). The local axis are Red, Green and Blue, where the red axis is the "1" axis, the green axis is the "2" axis and the blue axis is the "3" axis, which is the perpendicular (normal) axis. 
 With kind regards, 
 Dennis Waterman

Interfaces elements

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