Structural assessment of the south-west wing timber roofs of the Loreta in Prague

The Loreto of Prague is a remarkable Baroque historic monument, a place of pilgrimage with a captivating history. Behind the main façade, which is the marvelous work of the famous Dientzenhofers, there is a courtyard with a copy of the St. Mary´s Holy House of Nazareth. Since the placement of the first construction stone in 1626, the Loreto has faced many construction phases with many alterations. The majority of the works progressed between 1698 and 1748 under the supervision of Christoph and Kilian Ignaz Dientzenhofer. These alterations also generated some changes in the configuration of the roof structure and in some parts caused even damages. Some of interventions observed on timber frames are not documented and their purpose is not always obvious. For a better understanding, a historical analysis of the Loreto complex was used recently refined by dendrochronological dating of timber roofs elements from different time periods, so the historical chronology of the building could be accomplished. Afterwards, diagnostic tests were conducted on site for the health evaluation of the members to assess their condition. The mechanical parameters are obtained with the new diagnostic tool which is the loading jack and correlates well to the compressive strength parallel to fibers. Due to the historic interventions excessive deformation is observed in one of the timber frames. Utilizing the obtained health and mechanical parameters a numerical model of the south-west wing timber roof is modelled. From this global approach then is built a numerical model of the truss of concern and three scenarios are verified to achieve a possible hypothesis of the deformation. The structural numerical model provides valuable information of the existing deformation. Additionally, the current stability of the timber frame is assessed which proves to be safe under the actual conditions. In order to eliminate future problems for the truss two possible strengthening solutions are provided with the minimal intrusiveness on the historic timber roof.