Long-term Reliability of Historical Monuments Built with Low Quality Sandstone

摘要

The presented research concerns the long-term stability of a series of historical monuments, which were constructed with low-strength, ferrous sandstone. The main issues are the overall low compressive strength of the sandstone, the large scatter on these strength values, the sensitivity of its characteristics to water absorption and the lack of new original sandstone to replace the damaged zones. The sandstone reacts poorly under sustained high load levels, a situation which typically occurs at the base of bell towers and medieval city towers, as the dead load is considerably high compared to the compressive strength of the sandstone material. To assess the long-term behaviour of the sandstone, a test program has been set up to obtain information on its strength characteristics under monotonic and sustained loading. Therefore, test specimens were taken from the original material of a collapsed church tower. The results of these laboratory tests were used to adapt the parameters of an existing creep model to simulate the long-term behaviour of the sandstone under specific stress levels. Additionally, a number of strengthening solutions are discussed.