SSI1 - SHALLOW FOUNDATION MACRO-ELEMENT PROBLEM

02-Getting started with the modelling
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mrityun
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Joined: 28 Nov 2019, 04:12

SSI1 - SHALLOW FOUNDATION MACRO-ELEMENT PROBLEM

Post by mrityun » 28 Nov 2019, 05:55

I AM NOT ABLE TO USE SSI LINK ELEMENT DUE TO LACK OF INFORMATION. 1) THE SIX FOUNDATION INITIAL STIFFNESS COMPONENTS, INDICATED AS KN1, KH2, KH3, KM2, KM3, KM2, KTT FOR VERTICAL, HORIZONTAL AND ROTATIONAL DIRECTIONS BUT I AM NOT ABLE TO COMPARE THOSE COMPONENTS WITH GLOBAL DIRECTION (X Y RX RY ETC.). 2) HOW TO RESTRAIN RELATIVE MOTION AT GLOBAL Y AND VERTICAL DIRECTION CAUSE I AM CONDUCTING UNIDIRECTIONAL ANALYSIS (GLOBAL X DIRECTION). 3) SHOULD I CONNECT BASE NODES THROUGH BEAM?

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seismosoft
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Re: SSI1 - SHALLOW FOUNDATION MACRO-ELEMENT PROBLEM

Post by seismosoft » 29 Nov 2019, 12:20

As regards the element connectivity, the SSI elements are typical 6-DOF link elements, specially adapted so that to consider the the soil structure interaction. For the particular details on the SSI elements configuration, please refer to the help or the manual of the program.
The constraint of the DOFs it done in the typical way with the fixation of the corresponding node in the direction that you want constrained.
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mrityun
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Joined: 28 Nov 2019, 04:12

Re: SSI1 - SHALLOW FOUNDATION MACRO-ELEMENT PROBLEM

Post by mrityun » 10 Dec 2019, 05:49

Thank you for reply sir. I have already read the help and the manual provided by Seismo Struct but nowhere I have found the information. Actually I am willing to know that, in a global direction foundation stiffness parameters are Kx, Ky, Kz, Kxx, Kyy, and Kzz but in SSI1 link similar parameters are defined as KN1, KH2, KH3, KM2, KM3, KM2, and KTT. Now if I model a structure in global direction, then what is the sequence of KN1, KH2, KH3, KM2, KM3, KM2, and KTT as per the stiffness parameters in global direction? More specifically, I have calculated Kx, Ky, Kz, Kxx, Kyy, and Kzz as per the paper referred by seismo manual now KN1= Kx or Ky or Kz? a similar question arises for all other parameters (i.e. KH2=?, KH3=?, KM2=?, KM3=?, KM2=?, and KTT=?).

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seismosoft
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Re: SSI1 - SHALLOW FOUNDATION MACRO-ELEMENT PROBLEM

Post by seismosoft » 10 Dec 2019, 18:47

In SeismoStruct (and all other FE that we are aware of) the notations are on the local element axes.
In particular in the SSI elements: KN1 refers to the axial direction (local axis 1), KH2 & KH3 refer to the 2 and 3 local axes, KTT is the stiffness around the local 1 axis, and KM2 and KM3 are the rotation stiffnesses around the 2 and 3 local axes.
If the local 1 axis coincides with the vertical Z global axis, then KH2 & KH3 are in the horizontal global directions, KTT is the rotational stiffness around the vertical Z axes and KM2 & KM3 are the rotational stiffnesses around the two global horizontal axes X & Y.
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