Zoran Bonić

Comparative study on earthquake-induced soil–tunnel structure interaction effects under good and poor soil conditions

The effects of soil–tunnel structure interaction are proved to be quite significant, particularly under earthquake excitation. The influence of earthquakes on a tunnel–ground interaction depends on the peak acceleration, the intensity and duration of the earthquake, and outmost on the relative rigidity between the tunnel and the ground. With an aim to study the effects of tunnel–ground interaction, two-dimensional simplified dynamic linear analyses have been undertaken using the finite element based commercial software ANSYS. The present study employs a continuous FE model in order to estimate the soil–structure interaction effects regarding tunnel structures under earthquake action, for the cases of both good and poor soil conditions. The earthquake loading is simulated under simple shear conditions obtained by means of a one-dimensional free-field site response analysis in the code EERA. The obtained numerical results are compared to the most frequently used analytical expressions, and by that, a capability of the models to simulate the most important aspects of the SSI effects is validated. Furthermore, a comparison of the results for the cases of dense and loose soil conditions is performed, and their reliability, considerable mutual differences, as well as significant factors influencing tunnel–ground interaction for both cases, are evaluated.

Mathematical modeling of materially nonlinear problems in structural analyses, Part II: Application in contemporary software

The paper presents application of nonlinear material models in the software package Ansys. The development of the model theory is presented in the paper of the mathematical modeling of material nonlinear problems in structural analysis (part I - theoretical foundations), and here is described incremental-iterative procedure for solving problems of nonlinear material used by this package and an example of modeling of spread footing by using Bilinear-kinematics and Drucker-Prager mode was given. A comparative analysis of the results obtained by these modeling and experimental research of the author was made. Occurrence of the load level that corresponds to plastic deformation was noted, development of deformations with increasing load, as well as the distribution of dilatation in the footing was observed. Comparison of calculated and measured values of reinforcement dilatation shows their very good agreement.

Experimental Testing of Retaining Walls of Precast Elements

In contemporary construction practice is increasingly being applied flexible retaining structures of mechanically stabilized earth, gabions and precast elements. Although widely used only recently, their benefits are proven and widely accepted. The first part of the paper provides an overview of the possible ways of using of precast elements in the construction of retaining walls. The second part gives a detailed overview of the experimental testing of stability of retaining walls of prefabricated betonblok elements. The effect of static loads on the wall was examined in the first, and the effect of the dynamic loads in the second experiment. The results are analyzed and recommendations for future research are given.