Dafni Monastery, situated at approximately 10 km from Athens on the way to Eleusis, is one of the major Byzantine monuments in Greece (Millet 1899, Stikas 1962, Bouras 1998, Delinikolas et al. 2003). The Katholikon (main Church) of the Monastery (Figures 1 and 3) has suffered severe damages during the 7th September 1999 earthquake that affected the region ofAttica.

Immediately after the earthquake, a multidisci-plinary working group (Delinikolas et al. 1999) was formed by the Hellenic Ministry of Culture (HMC) with the assignment to do the necessary inspections, assess the nature and the significance of damages and elaborate, together with a Scientific Committee set to this purpose (composed by Professors Ch. Bouras, T. P. Tassios, E. Mariolakos and N. Zias) and all competent authorities of the Ministry, a strategic plan for the protection, conservation and restoration of the monument, its mosaics included.

Due to the severe damages of the structure and the danger of eventual aftershocks, the decision was taken for the application of emergency measures (Miltiadou-Fezans et al. 2003a). The aim of those measures was (a) to reduce the danger of further deterioration of structural damage and (b) to ensure accessibility and safe working conditions for all the scientific and technical personnel, thus enabling the execution of all the surveys and investigations, necessary for the design and implementation of the most adequate structural restoration interventions.

Figure 1. N-W view of the Katholikon of Dafni Monastery.

In parallel with the design and implementation of emergency measures, a first series of research programs were initiated, in order to record the state of the monument immediately after the earthquake. These programs were aiming at: (i) accurate survey of geometry (Georgopoulos et al. 2003), (ii) preliminary survey of damages, assessment of mechanical properties of construction materials, monitoring of the width evolution of main cracks, and preparation of a first detailed computer model of the monument used for preliminary structural analyses (Vintzileou, 2002) and (iii) assessment of the physicochemical characteristics of the construction and pointing mortars (Papagianni 2002).

The above research works were carried out in close collaboration with the responsible multidisci-plinary team nominated by the competent authorities of the HMC. On the basis of a synthesis of the obtained results, adequately completed with detailed in situ observations and archive researches, the mul-tidisciplinary group of the HMC has elaborated the structural restoration study (Delinikolas et al., 2003, Miltiadou-Fezans et al. 2003b). Following the proposals of this study, approved by the Scientific Committee and the Central Archaeological Council, it was decided to implement the structural restoration design and interventions in two phases.

Given the importance of the monument, a step by step multidisciplinary approach was adopted, both concerning the design and the implementation of the structural restoration interventions. Such an approach gives the possibility to start the execution of a series of interventions, and in the same time to perform the in situ and laboratory investigations that are necessary for the design of the next step. Furthermore, the assessment of the effect of the first step interventions to the structural behaviour of the monument can be carried out and taken into account for the design of the works of the second step. The first phase of interventions (that is completed) comprises measures taken to repair and strengthen masonry elements. The interventions of the second phase aim to improve the overall behaviour of the entire structure; their design is still in progress.

Moreover, within the HMC, it was judged as absolutely necessary to support the two phases of works with further research and investigations, comprising the design of adequate mortars and grouts, the experimental estimation of mechanical characteristics of masonry before and after grouting, the seismic monitoring of the structure, the application of NDT's for investigating invisible parts of the monument and controlling the grouting effect and efficiency.

In this paper, a brief synthesis of all the aforementioned investigations, studies, emergency and structural restoration works will be presented.

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