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Angel Francisco Martinez
November 19, 2018

Bridge 3D Soil Structure Interaction Methods Comparison




This session has been prepared upon the request by the Office of Earthquake Engineering in California Department of Transportations(Caltrans) due to the following reasons:

midas GTS NX(geotechnical software) can conduct nonlinear time history analysis on a bridge model with the soil modeled with solid elements that is supporting and surrounding bridge foundation. One of the significant reason is that it is compatible with midas Civil(bridge software). In short, a bridge model generated from midas Civil can be imported to midas GTS NX. The nonlinearities (i.e. plastic hinge) in the midas Civil bridge model can be imported in midas GTS NX. It can make a promising solution for applications in SSI study, liquefaction and lateral spreading issues.


This session, Bridge 3D Soil Structure Interaction Methods Comparison, will focus on (1) the soil structure interaction using indirect and direct methods and (2) the data exchange between midas Civil (bridge software) and midas GTS NX (geotechnical software). Following this session, we will have the 2nd session covering the Introduction to the Liquefaction in midas GTS NX on November 8th. As the last part, the 3rd session will be conducted covering the Verifications and Project Applications of the Liquefaction and Lateral Spreading Issues in early December (Exact date is TBD).


Overview of the Soil Structure Interaction (Indirect and Direct Methods)

Soil Structure Interaction studies are increasingly common in the field of civil engineering. Even though there are 2 main methods to perform this, most structural engineers use the Substructure (Indirect) Method given it is practical. The Substructure Method models the ground as springs applied to pile elements while the Direct Method models the soil in 3D elements connected to the substructure directly.

This session will cover the differences between the various ways of modeling the boundary conditions of a bridge and then contrast results by both SSI Methods (Indirect vs Direct Methods) using midas GTS NX and midas Civil under the same seismic loads.


Substrcture Method vs Direct Method


Soil Structure Interaction using midas Civil (bridge software) & midas GTS NX (geotechnical software)
Midas has the unique capability to import full structures into its 3D FEA geotechnical platform (midas GTS NX) from its bridge structural software (midas Civil), allowing it to perform realistic SSI through the Direct Method. The session will show the procedure to import the bridge as well as the modeling and meshing of the ground and substructure. It will proceed to compare 4 boundary condition cases for the same bridge under the same seismic load:
Bridge without substructure has a fixed base in midas Civil
Bridge is imported and substructure and ground is modeled in midas GTS NX
Bridge with substructure and soil springs are modeled in midas Civil
Bridge with substructure is imported and the ground is modeled in midas GTS

Both Methods Under Same Time History Acceleration



Presentation Slides










Speaker :  Angel Francisco Martinez

Category : Geotechnical

Software : midas GTS NX

Date : 2016-10-25





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