Title: Inelastic dynamic analysis of structures using Bouc-Wen hysteretic models
Type: PhD thesis
Submitted to: National Technical University of Athens
Date: April 2009
Language: Greek

This was my PhD thesis at the N.T.U.A. It was completed in April 2009 under the supervision of professor Vlasis Koumousis. Although it is written in Greek, all the main conclusion have been published in peer-reviewed international scientific journals in English. Feel free to contact me for details.

[abstract]

This PhD thesis raises and solves a number of theoretical and practical issues regarding the use of Bouc-Wen hysteretic models for the inelastic dynamic analysis of structures. Based on the definition of hysteresis and its rate independence, the Bouc-Wen model is reexamined in mathematical terms. New analytical solutions for the hysteretic response and the dissipated energy are derived which are based on Gauss’ hypergeometric function. These solutions form the stepping stone of a modified Bouc-Wen model which eliminates a significant problem of the original one, i.e. the local violation of Drucker’s and Il’iushin’s postulates of plasticity. This problem is known for decades and results in nonphysical behavior of the model in case of small amplitude reversals. The modified model is the most important contribution of the thesis. First, the extent of the nonphysical behavior is analyzed and quantified. Then, a modification of the original model is proposed which results in the correction of its aforementioned deficiencies. It is shown that the original and modified model may exhibit significantly different behavior under seismic excitation. In a more practical level, the identification of Bouc-Wen model parameters is examined. A new hybrid evolutionary algorithm is proposed which combines very good performance and stability. In addition, the important issue of experiment design is discussed based on the conclusions of parameter identification. In order to cope with the lack of experimental data, a new generic fiber model algorithm is also proposed which allows for the analysis of arbitrary crosssections under biaxial bending and axial load. All proposed methods and algorithms were programmed independently in computer code. Most of the code was also included in an existing 3D analysis software called “Plastique”, which has been developed by our research group. The validity and significance of the proposed methods is demonstrated through numerical examples.

[ PhD thesis]
[ PhD presentation]
[attached software : mySpec :  executable,  manual]
[attached software : myBiaxial :  executable,  manual]
[attached software : myBWID :  executable,  manual]
[attached software : myBWmod :  executable,  manual]
[attached software : myBWDE :  executable]