A correlation between damage and intensity on old masonry churches in Colima, Mexico by the 2003 M7.5 earthquake

Strong damage was observed in Colima Mexico on most of the cultural patrimony (mainly churches) after the 2003 M7.5 earthquake. In order to find a correlation between the observed damage on the historical buildings and the earthquake intensity, the vulnerability is assessed by qualitative methods, including the vulnerability class method (VCM) and the vulnerability index method (VIM). The latter method is modified and adapted in this research to assess the seismic vulnerability of historical buildings such as churches and cathedrals located in areas from high to very high seismicity. The results are intended to serve as preliminary indicators of expected damage levels that allow the local authorities to take measures oriented to disaster prevention. The assessment using both methodologies is developed on 15 historical masonry churches, most of them from XIX century. With the results, a correlation between damage and intensity taking into account a Macroseismic Scale is developed and the qualitative methodologies to assess the seismic vulnerability of historical constructions are compared each other.University of ColimaPolytechnical University of Guadalajar

Fundamental aspects on the seismic vulnerability of ancient masonry towers and retrofitting techniques

Ancient masonry towers constitute a relevant part of the cultural heritage of humanity. Their earthquake protection is a topic of great concern among researchers due to the strong damage suffered by these brittle and massive structures through the history. The identification of the seismic behavior and failure of towers under seismic loading is complex. This strongly depends on many factors such as soil characteristics, geometry, mechanical properties of masonry and heavy mass, as well as the earthquake frequency content. A deep understanding of these aspects is the key for the correct seismic vulnerability evaluation of towers and to design the most suitable retrofitting measure. Recent tendencies on the seismic retrofitting of historical structures by means of prestressing are related to the use of smart materials. The most famous cases of application of prestressing in towers were discussed. Compared to horizontal prestressing, vertical post-tensioning is aimed at improving the seismic behavior of towers by reducing damage with the application of an overall distribution of compressive stresses at key locations.Technical University of BraunschweigUniversity of FlorencePolytechnical University of Guadalajar

The use of prestressing through time as seismic retrofitting of historical masonry constructions: past, present and future perspective

Unreinforced masonry is one of the oldest construction materials and main component of historical buildings. Masonry is a heterogeneous material with an anisotropic behavior and may fail quasi-brittle during earthquakes. This paper describes the main components and arrangements of historical masonry, seismic vulnerability and existing retrofitting techniques, especially prestressing. Based on the evolution of prestressing, it is developed a future perspective about the use of this technique on cultural heritage. Especial attention may be taken into account when using this technique because the compressive strength may be exceeded, leading to an explosive brittle failure. The correct application of prestressing requires the designing of a compatible device and optimal post-tensioning force that improves strength and ductility without endangering the structure.Technical University of BraunschweigUniversity of FlorencePolytechnical University of Guadalajar

Seismic vulnerability and failure modes simulation of ancient masonry towers by validated virtual finite element models

Seismic protection of ancient masonry towers is a topic of great concernamong the scientific community. A methodology for the seismic vulnerability assessment of all types of towers and slender unreinforced masonry structures (e.g., light houses and minarets) is presented. The approach is developed by four validated 3D FEM models representative of European towers. The models are subjected to linear elastic investigations to establish load carrying capacity and dynamic properties for validation against similar towers. Seismic simulations are developed through intensive nonlinear static pushover analyses. From the assessments, the failure modes and overall seismic response of the towers are obtained. Low tensile strength of masonry and large openings at belfries have significant influence on the seismic behavior, resulting in a quasi-brittle failure. All the towers presented an imminent high vulnerability to seismic actions. The fewinvestigations reported in literature on the seismic behavior of towers are focused on in-plane behavior, disregarding out-of-plane behavior and toe crushing, both aspects are investigated in this paper. The more flexible towers are close to present toe crushing in both planes. The failure mechanisms are validated with reported post-earthquake observations on real damaged towers.Technical University of BraunschweigPolytechnical University of Guadalajar

Earthquake protection of colonial bell towers in Colima, Mexico with externally prestressed FRPs

A methodology for the seismic vulnerability reduction of old masonry towers with external prestressing is presented. It is applied at the Colonial bell-towers of the Cathedral of Colima, Mexico, characterized for being a high seismic area (M>7.5). The 3D FE models are calibrated with experimental data and assessed through nonlinear static approaches including the seismic demand and an accurate validated masonry model. Based on an extensive parametric study on different configurations of old masonry towers, it is selected an optimal prestressing force and device. The Colonial towers are retrofitted with four prestressing devices of FRPs to convert them into a high energy-dissipative reinforced masonry. The external vertical prestressing is included at key points identified in the seismic vulnerability assessment. This technique is in compliance with the demand for architectural conservation and may be located without drilling and unbounded in order to be fully removable. The seismic performance is enhanced by increasing force, displacement, and internal confinement. It is observed an upgrading of 35% and 20% of displacement capacity. With these results it is corroborated that external vertical prestressing allows a substantial increment of ductility for seismic energy dissipation purposes.ITESO, A.C.Technical University of BraunschweigUniversity of Florenc

Earthquake protection of colonial bell-towers in Colima, Mexico with externally prestressed FRPs

A methodology for the seismic vulnerability reduction of old masonry towers with external prestressing is presented. It is applied at the Colonial bell-towers of the Cathedral of Colima, Mexico, characterized for being a high seismic area (M>7.5). The 3D FE models are calibrated with experimental data and assessed through nonlinear static approaches including the seismic demand and an accurate validated masonry model. Based on an extensive parametric study on different configurations of old masonry towers, it is selected an optimal prestressing force and device. The Colonial towers are retrofitted with four prestressing devices of FRPs to convert them into a high energy-dissipative reinforced masonry. The external vertical prestressing is included at key points identified in the seismic vulnerability assessment. This technique is in compliance with the demand for architectural conservation and may be located without drilling and unbounded in order to be fully removable. The seismic performance is enhanced by increasing force, displacement, and internal confinement. It is observed an upgrading of 35% and 20% of displacement capacity. With these results it is corroborated that external vertical prestressing allows a substantial increment of ductility for seismic energy dissipation purposes

Seismic vulnerability assessment of historical constructions in the state of Colima, Mexico

The main purpose of this paper is to analyze and compare different qualitative methodologies to assess the seismic vulnerability of historical constructions in the State of Colima, which is located in a seismic area. The vulnerability is assessed by empirical methods, including the vulnerability class method (VCM) and the vulnerability index method (VIM), in order to perform preliminary indicators of expected damage levels that allow the local authorities to take measures oriented to disaster prevention. Results from the assessment using both methodologies of fifteen historical masonry buildings, most of them from XIX century, are compared with a real vulnerability index of every building from observed damage after the 2003 M7.6 Colima earthquake, according to the classification of damage in masonry buildings (EMS-98).University of Colim

Evaluación de la vulnerabilidad sísmica de edificios históricos en el estado de Colima por métodos empíricos

Este artículo presenta el análisis y comparativa de diferentes metodologías cualitativas para evaluar la vulnerabilidad sísmica de edificios históricos en el Estado de Colima. La vulnerabilidad es evaluada por metodologías empíricas, incluyendo el método de categorización o caracterización (MCC) y el método de inspección y puntaje (MIP), para obtener indicadores de daño esperado que permitan la prevención de desastres. Los resultados de la evaluación de quince edificios históricos usando ambas metodologías, son comparados con el índice de vulnerabilidad real de cada edificio mostrado tras el sismo de 2003 M7.6.Universidad de Colim

Erdbebenverletzbarkeit Reduzierung des historischen Mauerwerks Türme durch externe Vorspannung Geräte

This thesis describes a methodology to manage the seismic risk of historical masonry towers, including risk assessment and its reduction. First chapters describe the main aspects determining the earthquake hazard of a site, the structural vulnerability of towers and the recommended in literature to manage seismic risk. Since the seismic hazard is unavoidable, in this thesis the seismic risk reduction is attained by decreasing the structural vulnerability of towers by implementing prestressing devices. They are vertically and externally located inside the towers to give to the retrofitting the characteristic of reversibility, respecting in all senses the architectonic and historical value of the structure. This work addresses two main key stages on the seismic risk management of towers. The first stage corresponds to the assessment of seismic risk by combining intensive numerical simulations and a suitable masonry model. To obtain models more reliable and representative they are validated with key-behavioural characteristics reported in literature, observed damages and calibrated with experimental data. Prestressing intends to improve the seismic performance of towers by reducing the expected damage with the application of a pre-compression to the masonry to increase strength, ductility, energy dissipation and confinement, achieving with these the seismic risk reduction. The risk assessment of historical towers and the possible achievement of the risk reduction are the main characteristics of the proposed methodology. The second key stage corresponds to the validation of the proposal in two real historical towers located in seismic zones of Mexico and Italy. Finally, advantages and limitations of this proposal in the seismic risk management of historical masonry towers are described.Hier steht eine Methodik, um seismischen Risikos der alten Mauerwerks Türme, einschließlich Risikobewertung und seine Reduktion zu verwalten. Ersten Kapitel beschreiben wichtigste Aspekte Bestimmung der Erdbebengefährdung, strukturelle Anfälligkeit der Türme und die seismische Risiken zu steuern. Seit die seismische Gefährdung unvermeidlich ist, hier wird die seismische Risikoreduktion durch Verringerung strukturellen Verwundbarkeit der Türme durch Umsetzung Vorspanneinrichtungen erreicht. Sie befinden sich vertikal und extern in den Türmen, um Nachrüsten die Charakteristik der Reversibilität geben, respektieren das historische Wert der Struktur. Hier befasst sich im Wesentlichen zwei wichtigen Phasen auf seismische Risiko-Management von Türmen. Erste Stufe entspricht der Beurteilung der seismischen Risikos durch numerischen Simulationen und ein geeignetes Modell Mauerwerk. Vorspannung soll die seismische Leistung der Türme durch Verringerung erwarteten Beeinträchtigung der Durchführung einer Vorverdichtung auf das Mauerwerk, um Resistenz, Festigkeit, Duktilität, Verlustleistung und Anbindung erhöhen, wodurch eine Verringerung der seismische Gefahr zu verbessern. Zum Erreichen der Modelle zuverlässiger und repräsentativer sind mit Schlüssel-Verhaltensmerkmale berichtet validiert werden, beobachteten Schäden und kalibriert mit reale Daten. Vorspannung beabsichtigt, seismische Leistung von Türmen durch eine Verringerung der erwartenden Schäden durch Einsatz eines Pre-Kompression, um das Mauerwerk zur Festigkeit, Zähigkeit und Energieaufnahme zu erhöhen, um mit diesen der seismischen Risikoreduktion Verbesserung zu erreichen. Risikobewertung von Türme und die Leistung der Risikominderung sind Hauptmerkmale der vorgeschlagenen Methodik. Die zweite Phase ist die Validierung des Vorschlags in zwei alten Türme in Erdbebengebieten von Mexiko und Italien. Schließlich werden Vor- und Nachteile dieses Vorschlags im seismischen Risikomanagement historischen Türme beschriebt

Seismic vulnerability enhancement of medieval and masonry bell towers externally prestressed with unbonded smart tendons

Medieval and masonry bell towers are highly vulnerable to suffer strong earthquake damage due to the mechanical and physical characteristics of masonry and other important factors. An approach for the seismic vulnerability reduction of masonry towers with external prestressing is proposed. The devices are vertically and externally located in order to be removable when needed. The characteristic flexural failure mode of medieval towers and the shear mechanism of bell towers are simulated. Both failure modes are in agreement with earthquake damage in similar towers. Medium prestressing level enhances force capacity of towers failing by bending without reducing ductility. High prestressing level slightly reduces the displacement capability of towers failing ductile. In case of belfry failure, both prestressing levels permit to increase displacement but lower force than towers failing by bending. The proposed medium prestressing level is the optimal for masonry towers and other slender structures failing by bending and shear.ITESO, A.C.Technical University of BraunschweigUniversity of Florenc