Major outcomes of the FLIP research committee phase 4 (July 2007 through June 2011) are as follows:

Upgrading of FLIP program

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FLIP program was upgraded as follows:

FLIP2D

Fundamental modification for cocktail glass model (name changed from the previous name of “new dilatancy model”)

Extension of cocktail glass model (steady state, tmp7 method, stiffness matrix formation, iterative numerical procedure)

Modification of cocktail glass model for improving the performance in the vicinity of failure line

Separation of pore water element into partially drained analysis and fully undrained analysis with enhanced stabilization procedure for partially drained analysis

Asymmetric modified Takeda model as a order(user)-made beam element

Nonlinear soil-pile interaction spring for cocktail glass model

Stabilization scheme for simplified large deformation analysis

Enhanced computation time for coupled u-p analysis by re-numbering of variables

Permission to change the Rayleigh damping factors at re-start for improved stability during the computation phase for dissipation of excess pore water pressure

Eigen value analysis of 2D soil-structure systems

Other improvements

FLIP TULIP (Total and Updated Lagrangean analysis of Liquefaction Program)

Large deformation (finite strain) analysis based on FLIP 2D for incorporating geometric nonlinearity effects

FLIP3D

Automatic determination of stabilization parameters AA, BB for assigning fictitious confining stress for soil at or near non-confining stress state

External numbering by user specified numbers for nodes, elements, and materials (sequential internal numbers are generated in the program)

Visualization of multiple stage construction analysis (specification of KILL or reference displacement stage)

Joint element referring to the effective stress state of neighboring soil element ring

Modification of 3D multiple spring model (better fit to triaxial cyclic test results)

Eigen value analysis of 3D soil-structure systems

3D cocktail glass model

Other improvements

Support programs (pre- and post- programs)

FLIPSIM: general upgrading (including multiple plotting of liquefaction resistance curves, etc.)

FLIPSIM: simplified parameter determination method (3rd revision)

FLIPCSIM: parameter determination for cocktail glass model

FLIPGEN: general upgrading

Other improvements

Studies on advanced applications of FLIP program

Studies have been made on advanced applications of FLIP program with the following themes by working groups (WG) .

Improve basic constitutive equation of cocktail glass model element (previously called “new dilatancy model element”) Enhance applications of constitutive equation of cocktail glass model element (add Sus method, add tmp7 method, modify tangential stiffness matrix, change modified nonlinear iterative procedure ) Modify constitutive equation for improving the behavior of cocktail glass model element near the failure line Divide pore water element into two elements; one for undrained condition and the other for drained condition. Modify functions for stabilization of analysis using pore water element under partially drained condition Introduce asymmetric modified Takeda model element as a user-defined element Introduce pile-soil interaction spring element corresponding to cocktail glass model element

Results of the research work through these working groups were summarized as the research reports to the members of the FLIP research committee. Some of the results were made available to the wider area of engineers and researchers as follows:

Short list of references in English (long list of references are available in Japanese HP)

1）	Tamari Y., Ozutsumi O., Iai S., Yokoyama N.: A numerical study on post liquefaction soil behavior by dynamic effective stress analysis, Performance-Based Design in Earthquake Geotechnical Engineering, Kokusho, Tsukamoto & Yoshimine (eds), Taylor & Francis Group, London
2）	Suzuki A., Ozutsumi O., Iai S., Yokoyama N.: A study on prediction accuracy of the dissipation of pore water ) pressure and the settlement of soil surface for an actual case by the dynamic effective stress analysis program, Performance-Based Design in Earthquake Geotechnical Engineering, Kokusho, Tsukamoto & Yoshimine (eds), Taylor & Francis Group, London, 2009.
3）	Fujii N., Sawada S., Iai S., Ichii K., Yokoyama N., Ozutsumi O., Nakahara T., Mizuno K.: Model modification considering steady state for dynamic analysis, International Conference on Performance-Based Design in Earthquake Geotechnical Engineering — from case history to practice —, 2009.6.

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