Due to the low tensile resistance of historical constructions formed by stone blocks, these structures are particularly vulnerable objects under lateral seismic loads. In this way, the study based upon the assumption of continuum structures would not be realistic for many cases. On the other hand, models based on rigid-block assemblies provide a suitable frame work for understanding their dynamic behavior under seismic actions. In this context, the problem is primarily concerned with Rocking Motion (RM) dynamics.
Some authors have been used successfully the Distinct Element Method in the study of block structures. However, they have used experimental test to calibrate their models and to obtain the parameters used in the DEM; because, these parameters can not be obtained in a direct form from the parameters of the stones. Special attention regards about the damping factor, since in the DEM a viscous damping is considered, but in the reality, the damping is due by impact that can be considered as a type of Dirac-delta forces.
This paper is divided in two parts, in the first one, a methodology for the modeling the dynamic behavior of rigid-block structures under seismic loadings by means of a Distinct Element Model is proposed. The commercial code UDEC was used. The methodology proposed links the parameters used by the UDEC and the theoretical parameters used by the classical theory of RM, since these last parameters can be obtained by means of theoretical expressions or by experimental test.
In the second part, the paper presents the modeling of the block structures tested at the Laboratory of Civil Engineering (LNEC) of Portugal. Single block and bi-block structures were studied. The experimental tests were carried out at the seismic table of the LNEC. Free rocking, harmonic and random motions were used in the experimental tests. Very good agreement between the numerical model and experiment is achieved, for both free and forced regimens.