Protection of Historical Structures and Interventions for Repair and Strengthening with Emphasis on Antiseismic Conservation

It is not certain that a historical and monumental building that sustained successfully the effects of previous earthquakes will endure the forthcoming ones. In most cases, previous earthquakes have already caused minor or major non-structural or structural damage. The accumulation of this damage may severely affect the antiseismic performance to a future earthquake with larger acceleration, velocity and displacement values and its effects especially when other damaging factors including physicochemical decay of structural settlements, differential settlements, possible fires among others, have caused further reduction of the bearing capacity of the building. Thus, the need for the preservation of historical and monumental buildings and their strengthening against seismic risk and related damage is evident and crucial. All methods and techniques of preservation and strengthening should be applied to these structures with the least possible alteration of their form. Besides the preservation of these cultural objects, the need for their antiseismic performance is dictated by the legal obligation to ensure safety and health of residents, neighbors, visitors and conservators of the structure. This aspect of interest in the bearing capacity of historical and monumental buildings is of great importance in modern society. © 2019, RILEM

Investigation of the Seismic Response of a Byzantine Church and Evaluation of the Effectiveness of Proposed Interventions

The seismic response of the twelfth-century Byzantine church of Panhagia Krina in Chios, Greece, is investigated in this paper. The numerical model implements all the details of the geometry of the structure and is validated by comparison of the dynamic characteristics with ambient vibration measurements. Time-history elastic analyses are performed for selective seismic motions, chosen to comply with the expected ground motion in the area. The results show that the linear elastic approach can predict the existing damage quite accurately and explain the collapses that occurred during the 1881 earthquake. The effectiveness of several interventions is also examined; in some cases, cracks were introduced in the model to overcome the limitations of the elastic analysis. The proposed interventions enhance the structure but they cannot eliminate the possibility of severe damage or even local collapses during future seismic events. This is because there are inherent problems in the structure, e.g., the large size of the dome of the main church compared with the overall size of the structure and the structurally weak system of support of this dome. </jats:p

Using Earthquake-Induced Damage on Historical Constructions for the Detection of the Basic Seismological Parameters of Historical Earthquakes

Earthquake-induced damage on historical constructions can reflect the basic characteristics of earthquakes including epicenter location, the seismogenic fault type, the focal depth and the seismic intensity based on the application of macroseismic scales. Taking into account historical buildings response to recent earthquakes, it is concluded that shallow near-field events caused similar building damage. Symmetrical buckling and compression damage of structural elements, bursting of over-stressed elements, symmetrical distribution of damage around a vertical axis and other spatial homothetic motions reflect shallow near-field earthquakes with prevailing vertical component of the earthquake ground motion. Following this approach based solely on field macroseismic observations on historical structures, important conclusions related to historical earthquakes may be drawn. In the case of the 1755 Great Lisbon earthquake, data derived from on-site inspection of well-preserved still-standing damaged historical buildings in Lisbon and artworks illustrating buildings that suffered damage from this sequence were used. In brief, the studied buildings present damage with symmetrical distribution around a vertical axis and partial collapse of upper parts within their footprint. Based on the aforementioned, this damage is attributed to a shallow earthquake with epicenter located very close to Lisbon, a strong vertical component and perhaps of not so great magnitude preceding or following the 1755 Great Lisbon earthquake with epicenter determined in the ocean to the west of Lisbon and generated the devastating tsunami. It is suggested that the aforementioned approach can be applied either in historic earthquakes or complementarily in recent events when the available seismological information are inadequate. © 2019, RILEM