Maria-Eleni Dasiou

Seismic Behaviour of the Walls of the Parthenon A Numerical Study

A numerical study of the behaviour of the walls of the Cella of Parthenon subjected to seismic loading is presented. Commonly used numerical codes for masonry structures based on continuum mechanics are unable to handle the behaviour of discontinuous walls of ancient monuments, in the same way as continuum models cannot capture the behaviour of drum-columns. In this analysis, the discrete element method was used, which has been proven, in previous research, capable to accurately predict the response of discontinuous structural systems. The marble structural stones of the walls were modeled as rigid blocks with frictional joints between them. Two types of models were used in the analyses: (i) a sub-assembly consisting of only a section of the wall of limited length, either as it is in-situ (partially collapsed) or with its full height (restored) and (ii) considering the whole structure partially restored. In one of the models of type (i), the existing damage of the stones was also implemented. Analyses were performed with and without considering the metallic elements (clamps and dowels) that connect adjacent stones. The numerical models represented in detail the actual construction of the monument. The assemblies considered were subjected to all three components of four seismic events recorded in Greece. Time domain analyses were performed in 3D, considering the non-linear behaviour at the joints. The general response profile was examined, as manifested by rocking and sliding of individual stones or groups of stones. The effect of several parameters was investigated including: the coefficient of friction at the joints, the imperfections of the blocks, the existence or not of connectors between adjacent blocks and the seismic motion characteristics. The results of the sub-assembly models and the full-structure model were compared in order to estimate the accuracy of the sub-structuring technique. The effect of the restoration of the wall to its original height was also examined. Conclusions were drawn based on the maximum displacements induced to the structure during the ground excitation and the residual deformation at the end of the seismic motion.

NUMERICAL INVESTIGATION OF THE SEISMIC RESPONSE OF HEPHAESTUS TEMPLE IN ATHENS, GREECE

In this paper, the seismic response of the Temple of Hephasteus in Athens, Greece is investigated numerically. The temple of Hephaestus was probably erected between 460 and 420 BC by a yet unknown architect on top of Agoraios Kolonos hill, which is delimiting the Ancient Agora of Athens to the west. It is one of the best preserved ancient temples, partly because it was transformed into a Christian church. The analyses were performed using the general purpose code 3DEC, which is based on the distinct element method, and can capture well the dynamics of multi-block systems, which respond to strong earthquakes with intense rocking and sliding of the individual blocks. The ground motions that were used as base excitations were selected to be compatible with the seismotectonic environment of the ancient center of Athens and within the range of the maximum expected earthquakes. In the numerical model, the full monument was implemented, but an investigation of the accuracy obtained with sub-models concerning small parts of the temple was also performed. The structural members were simulated quite accurately, but the columns and the walls were modeled intact, without the imperfections and the damage observed in the current state of the monument. However, the computer codes that were used were producing damage to the structure after each earthquake. In this way, it was possible to evaluate the effectiveness of the used software by comparing the predicted damage with the existing one.

Numerical Evaluation of the Seismic Efficiency of Connections of Fractures and Complements of Ancient Colonnades

As a common practice, restoration projects of ancient colonnades have to deal with joining together fragments of architectural members using threaded titanium bars (reinforcement) fixed into place with cement mortar. The basic criterion for the design of such connections is that, in case of a seismic event, the reinforcement should absorb the seismic energy and fail before the marble suffers any damage. For the dimensioning of these connections, the capacity design concept is usually implemented. In this chapter, the efficiency of the reinforcement of the connection calculated with this methodology is investigated for selected severe seismic excitations. The analyses were performed for two case studies with different geometries: a column of the Parthenon Pronaos and the Southern colonnade of the Ancient Agora of Kos in Greece. The induced forces were calculated using the distinct element method. The results show that the design is adequate, as the stresses induced to the reinforcement bars were always less than their ultimate strength and, in many cases, considerably less than their yield resistance as well.