Safeguarding Condition of the Rock- Hewn Churches of Lalibela’ presented by Naol Gebeyehu Duguma

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Addis Ababa University


This research focuses on the wind and structural analysis of the steel canopy structures shading five of the eleven monumental churches, Bete-Mariam, Bete-Mesquel, Bete-Medhaniealem, Bete-Abalibanos and Bete-Amanueal, found in Lalibela. This world-renowned site with the rockhewn monuments is one of the important heritage sites in Ethiopia, which is registered and protected by the United Nations Educational, Scientific and Cultural Organization (UNESCO) since 1978. Currently, the shades sheltering the five rock-hewn churches are showing visible signs of failure at the base of the columns, which is one of the main reason for doing this research. A numerical analysis is performed on an underground tunnel, on which one of the columns of the shade sheltering Bete-Amanueal is directly placed. The current shelters are implemented with a design change for a reason that UNESCO found the previous design too permanent. However following the design change there is no investigation carried out to properly identify the characteristic behavior of the subsurface condition. These, coupled with the conjecture of the uplift wind loading creating instability, has created the fear that the failure of the canopy shelters may result in extensive damage or even total failure of the rock-hewn churches. In this study, the structural safety of the steel canopy structures is investigated based on the raw wind data collected from the National Metrology of Ethiopia for the Lalibela area. The design basic fundamental wind speed is decided based on the probability distribution, which best fits with the available data. The wind load analysis performed on the structure clearly shows that the uplift wind is critical and is likely to cause further structural damage to the canopy structures. Based on this finding, long term and alternative short-term mitigation measures are discussed considering constraints, such as simplicity, non-labor intensiveness and compliance with the UNESCO regulations specified for the shelter project. The rock mass has also been studied and classified using one of the multi-parametric rock mass classification methods, the Rock Mass Rating (RMR), to quantify the in-situ condition of the tunnel.



Rock-hewn church, Lalibela Monuments, Wind Loading, Canopy Roof, Steel shelters, Underground Tunnel/Cavity, Numerical Analysis