Structural Restoration Study of a 'neoclassical' house in Chalkida
Summary of the MSc Thesis on Restoration of Architectural Monuments
The project of the present dissertation is the structural restoration of a two-storey building. The structural components are studied and described first, followed by the numerical modelling and dynamic analysis. Numerical models are created for the situations both before and after application of the reinforcement proposals.
The building under study is situated in the historic centre of the city of Chalkida. Today it is one of the town’s few remaining samples of late 19th century architecture. The building is situated just a few meters from the promenade, an area that used to be inhabited by the middle classes, mostly merchants. However, wealthier people also lived in important buildings in the vicinity.
The building was constructed during the 1880s. During that period the town plan was enforced by law and thus various changes took place up to the beginning of the 20th century. Most old buildings were demolished and others were constructed in their place. The ground plan of the rooms and the large number of entrances show that this structure had a double use. The remarkable morphological and decorative features on the building’s frontage and interior rendered it a monument in 2001 by decree of the Ministry of Culture. 
The building is a typical sample of the late neoclassical period, comprising three main parts: stand – ground floor, scape – storey and ridge – roof. Supporting walls are the basic feature of the load bearing structure. The wall thickness varies, gradually decreasing towards the top of the building. The walls of the basement and ground floor consist of stonework with the exception of the corners of the frontage, which are made of large heavy sandstones. Their construction quality is better at the front than the back side of the building. The first floor is made of solid brick.
Moreover, there are INP-shaped metal girders in order to support the thin internal walls between rooms. The floors consist of a parallel wooden girder system. The roof also consists of a complex system of wooden girders and props with metal joints connecting each other. Ceramic tiles were used to cover it.
ETABS finite element program was used for the simulation and analysis. Three models were created in order to describe the behaviour of the building in its present unsupported state and its state after the two sets of proposed reinforcement measures have been applied. These measures include making the floors act as diaphramgs and increasing the wall ductility by covering them with a reinforced concrete jacket of a few centimetres.Frame elements were used for modelling the girders and roof, whereas vertical and horizontal shell elements were used to model the supporting walls and floor diaphragm. The simulation of the reinforced concrete jacket on the walls was achieved by increasing the modulus of elasticity of the existing walls. In modelling the foundation, all degrees of freedom at the joints at basement level are limited and fastened (fully fixed end conditions).
Eurocode 6 was used to determine the wall strength, taking into account some in situ experimental test results for determining the mortar strength (impact hardness testing), while empirical values were used for the sandstone and brick strength. The dynamic spectral method was used to define the stress due to seismic loads. The analysis is performed for load combinations that take into account all three directions of the seismic loading. Analyses were also performed for two limit states: serviceability and ultimate. Graphs of the vertical and shear stresses in the walls due to various load combinations are presented herein. Moreover, figures of the deformed shape for the entire structure are presented for the predominant modes. The dissertation is completed with the interpretation of the results and the assessment of the building’s behaviour under the influence of vertical and seismic loads through observation and comparison of the graphs. Assessment of the efficiency of the proposed restoration measures is also presented. Finally the philosophy of the restoration measures is presented, followed by the full design and detailing.
In conclusion, the advantages offered by the finite element method in presenting the results of the analysis must be duly noted. It renders it possible to achieve the best possible image of the structures’ stress state, distribution and concentration of stresses, definition of sensitive points, as well as variations due to changes in geometry and construction materials.