建築工学技術

抽象的な

Preliminary Structural Analysis for the Archaeological Reconstruction of the Ancient Palace Grat Be'al Gibri in Yeha, Ethiopia

Martin Drieschner, Sigrid Wilhelm, Yuri Petryna, Mike Schnelle, Iris Gerlach

Unique objects of cultural heritage are usually thoroughly investigated from the archaeological viewpoint. However, lots of relevant questions regarding these objects remain still open without specific investigations from the engineering viewpoint, especially those of ancient construction knowledge and technology. The present work is a preliminary attempt to apply modern engineering tools to study a virtual structure of an ancient building in Ethiopia which has been reconstructed within the framework of an Ethiopian-German cooperation project before. The palatial building called Grat Be'al Gibri in Yeha is the largest preserved structure of its kind in South Arabia and North-East Africa. Its special feature is the construction of the walls consisting of timber-laced rubble masonry. There are indicators that it could be a multi-story building, although only parts of the ground floor and its wall constructions are preserved. The engineering investigations should help answering a few important questions regarding this building, among others about the ground plan form, thickness of the walls, the function of timber beams for the wall, their placement and orientation as well as a potential story number in the building. For this purpose, the building is tentatively investigated from the structural viewpoint taking into account enormous uncertainties with respect to structural and material parameters. Based on the 3D geometrical (CAD) model of the building available from the archaeological reconstruction, a numerical linear elastic macro model within the finite element method has been developed for all structural simulations within this study. The walls are assumed to consist of a homogeneous material whose properties are estimated from the relevant literature and are taken into account by their minimum, mean and maximum values within some physically reasonable ranges. The detailed modeling of a heterogeneous timber-reinforced masonry structure of the walls on the meso scale is omitted in this first step. The structural performance under dead load is evaluated with respect to the overall spatial deformation and principal stresses on critical locations. Based on the obtained results, it is finally proposed by the authors which next steps should be done for further investigations to answer archaeological questions which could not be answered yet.