Experimental and numerical study of a fractured marble epistyle restored with layers of titanium bars

Abstract

Abstract. The mechanical behaviour of fractured prismatic marble architraves (epistyles) is evaluated in the present study both experimentally and numerically. The study is based on a recently introduced method for the calculation of the reinforcement required for joining together fractured structural elements of ancient monuments. The experimental assessment includes the construction of an accurate model of the most seriously damaged architrave of the north colonnade of the Parthenon Temple in a scale 1:3. The epistyle is considered symmetrically fractured at its mid-plane and it is restored with three horizontal layers of titanium bars. A multi-point bending arrangement was designed including a system of double T-beams and steel rollers in order to approach in an optimum manner the action of the uniformly distributed load exerted on the epistyle in its original position. A numerical analysis followed in an effort to study the parameters influencing the behaviour of the epistyle. The numerical model simulated accurately all the geometrical details of the experimental model, the load application mode and the mechanical characteristics of the three materials used for the restoration (marble, titanium and interposed cementitious material). The analysis enlightened interesting points concerning the location of the regions of the structure more susceptible to failure.

Acoustic Emissions versus Pressure Stimulated Currents during bending of restored marble epistyles: Preliminary results

“…its portion under tension). In a second phase cracking of the layer of cement paste that fills the holes and surrounds the metallic bars appears in the immediate vicinity of the interface (recall that according to previous numerical studies it is only a small portion of the anchoring length -equal to a few cm -that undertakes the tensile force balancing the externally applied bending load [8][9][10]). During the remaining time-intervals the element suffering from cracking is the body of the two marble fragments.…”

“…This is very interesting since the specific failure mechanism seriously concerns the members of the scientific personnel working for the restoration of the Acropolis monuments [37,38]. Indeed, it has been verified both in the laboratory and also in the worksite that the weak link of the three-material complex (marble-cement paste-titanium) is the interface between the marble and the cement paste which due to pure adhesion fails prematurely [8][9][10]. It is mentioned, however, that the specific failure mechanism is not always "unwelcome", since it may act as a protective mean against failure (fracture) of the authentic marble body itself.…”

“…The aforementioned technique is based on the basic restoration principles, dictated by the "Venice Charter" [4,5]: Reversibility (if needed, the monument could be brought to its state prior to the intervention), minimization of the interventions to the extent that guarantees protection of the authentic material from further damage (for this reason the number of titanium bars required by the connection's design, should be the smallest possible) and finally compatibility between the materials used for the restoration and the authentic ones. The restoration approach described above was assessed a few years ago both experimentally and numerically [6][7][8][9][10]. It has been indicated that, in spite of its efficiency and general acceptance, there are still some open issues that should be further studied, mainly in the direction of reducing the intervention on the authentic building material.…”