Experimental Evaluation of the Out-Of-Plane Behaviour of Traditional Stone Masonry Buildings in Azores, Portugal (original) (raw)
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Out-of-plane behaviour of existing stone masonry buildings: experimental evaluation
Bulletin of Earthquake Engineering, 2012
Masonry structures can be considered as the simplest type of structures concerning its assemblage but, at the same time, it is one of the most complex construction materials in terms of mechanical properties and correct behaviour assessment. In this context, the work herein presented aims at describing an experimental testing campaign recently carried out in order to characterize the out-of-plane behaviour of traditional masonry constructions. Taking advantage of the existence of a traditional two-storey masonry building abandoned after the 1998 Azores earthquake, several in-situ tests were defined and performed with the application of quasi-static cyclic loads at the building top level in the out-of-plane direction. In addition, the efficiency of retrofitting and/or strengthening techniques applied during the 1998 Azores reconstruction process was also experimentally evaluated. Finally, an overall discussion of these techniques is presented, resorting also to previous tests' results carried out by the same authors, aiming at inferring and suggesting quantifications of strengthening techniques' contributions for future interventions on existing buildings. For this purpose, simple analytical mechanical approaches were adopted in order to provide numerical estimates of strength that were found in good agreement with the experimental results.
Experimental In-Situ Testing of Typical Masonry Constructions of Faial Island - Azores
2008
The present paper focuses on an in-situ testing campaign recently developed in the Faial island, Azores, Portugal, aiming at the assessment of the out-of-plane behaviour of traditional stone masonry walls. This experimental activity, carried out by the Laboratory for Earthquake and Structural Engineering (LESE, FEUP, Porto), started developing some years after the Faial/Pico earthquake on July 9th 1998, in order to provide adequate characterization of the structural response under loading types likely to induce out-of-plane motion of walls as the case of the seismic action. A general description is included concerning cyclic tests carried out to date, complemented with the presentation and discussion of the most important results. Numerical predictions of strength based on simple models are also provided for one tested wall indicating good agreement with experimental findings. This in-situ programme involved a second stage for structural strengthening according to schemes similar to some of those adopted during the reconstructions process in Faial Island. Further tests were then performed in order to assess the seismic capacity improvement of the strengthened structures, leading to interesting and promising results concerning both strength and energy dissipation enhancement. The paper also highlights that such type of tests is viable and constitute an excellent means of assessing structural parameters for masonry walls as they exist in reality, in order to feed suitable non-linear behaviour models for structural analysis.
2010
This paper presents the main results of experimental tests concerning the assessment and reduction of the seismic vulnerability of stone masonry buildings with flexible floors. The “gaioleiro” building typology, which probability presents the highest seismic vulnerability of the housing stock of Portugal, was used as case study. The tests were performed in the LNEC 3D shaking table by imposing artificial accelerograms in two horizontal uncorrelated orthogonal directions, triggering in-plane and out-of-plane response of two tested mock-ups; one in original condition and another repaired. The preliminary results show that the adopted measures are efficient, allowing to improve the seismic performance of this building typology.
A Review: 7000 Years of Building Structures
JADA, 2024
The purpose of this review article is to examine the changes and developments in structural systems and materials up to the present day through a holistic perspective, considering the societal dynamics of each period. The article includes a literature review and investigates the development of structures through the concepts of "structural system," "construction material," and "structural innovation." In selecting the structures discussed in the article, care has been taken to include those that pioneered new structure types, and/or materials for subsequent structures. The study covers an approximately 7,000-year period from the Neolithic era to the present. Therefore, within this broad time frame, the article provides brief/concise information on the concepts of "structural system," "construction material," and "structural innovation" about the examined structures. In the study, it is observed that until the Industrial Revolution, building construction was carried out using traditional materials and construction techniques. Moreover, faith was a major motivation in pushing the boundaries of construction techniques under the conditions of the time. This motivation changed with the Enlightenment era, as the new thought process resulting from the Industrial Revolution replaced the motivation of "faith" with "building for society" through new technological possibilities. New forms of society brought with them new construction technologies and typologies. This situation persisted until the late 20th century, but it changed with the use of computer technology in design and construction phases. Since then, structural concerns, which had been a significant constraint in building construction, have become less of a priority for designers. From this point of view, the article is structured as follows after the "Introduction" section: "Building for Faith: The Limits of Traditional Materials," "The Machine Age: Building in the Light of Modern Science and Engineering," and "Free from Structural Constraints: The Impact of Computers." In the conclusion, examples are listed according to the concepts of "structural system," "construction material," and "structural innovation," thereby presenting the results of the study.
Aspects of Seismic Assessment and Redesign of Traditional Masonry Buildings
Most of the traditional greek buildings (new-classic ones or not, small or large), with an age of more than 75 up to 250 yrs, are made of rubble stone masonry with a large volume of low strength lime mortars, while their floors/roofs are mainly made of timber. Their seismic assessment and redesign, based on recent conceptions and normative or informative code principles and criteria, is a challenging problem for the Structural Engineer, not to mention restrictions imposed due to the monumental character of almost all of these old buildings. To this end, the new “frame” of Euro-Codes, and especially of EC 6 and EC 8, is applied in general, as recently completed by the new Greek Codes on (Structural) Assessment and Interventions (nGCSI, 2012), fully harmonized with this “frame” of ECs but far beyond them and more detailed, with a lot of relative application rules. Several aspects are involved in structural assessment and redesign of such old buildings, as covered by the Codes and shortly presented/discussed in this paper, such as : Investigation and documentation of the geometrical and the mechanical data of the existing building, together with their reliability levels (DRLs), i.e. the so-called “knowledge levels”, influencing almost all phases and steps of the design; Quantitative assessment and documentation of any wear, deterioration or damage, of any kind, together with a practical but reliable and safe assessment of the residual mechanical characteristics, based on damage levels (DLs); Decision regarding the performance level (PL), i.e. the foreseen or expected degree of damage during the earthquake itself, probably different for the assessment or the redesign of the structural interventions; Aspects of mechanical behaviour of the masonry (and other) elements, out-of-plane and in-plane response, macro-models etc., before and after repair or/and strengthening, as well as Methods of analysis and dimensioning or redimensioning, linear and non-linear, checks in terms of force or of displacement, depending on PLs and based on skeleton curves. In this paper, most of the related issues are shortly covered, as faced during the structural design, while certain characteristic examples and applications are presented.
Seismic performance of an unreinforced masonry building: An experimental investigation
Earthquake Engineering & Structural Dynamics, 2009
This paper presents the results of an experimental investigation carried out to investigate the seismic performance of a two storey brick masonry house with one room in each floor. A half-scale building constructed using single wythe clay brick masonry laid in cement sand mortar and a conventional timber floor and timber roof clad with clay tiles was tested under earthquake ground motions on a shaking table, first in the longitudinal direction and then in the transverse direction. In each direction, the building was subjected to different ground motions with gradually increasing intensity. Dynamic properties of the system were assessed through white noise tests after each ground motion. The building suffered increasing levels of damage as the excitations became more severe. The damage ranged from cracking to global/local rocking of different piers and partial out-of-plane failure of the walls. Nevertheless, the building did not collapse under base excitations with PGA up to 0.8g. General behaviour of the tested building model during the tests is discussed, and fragility curves are developed for unreinforced masonry buildings based on the experimental results.
Canadian journal of civil engineering, 2007
The results of lateral resistance tests of masonry walls and shaking table tests of a number of models of masonry buildings of various structural configurations, built with various materials in different construction systems, have been analyzed to find a correlation between the occurrence of different grades of damage to structural elements, characteristic limit states, and lateral displacement capacity. On the basis of correlation between acceptable level of damage and displacement capacity, it has been shown that the range of elastic force reduction factor values used to determine the design seismic loads for different masonry construction systems proposed by the recently adopted European standard Eurocode 8 EN-1998-1 for earthquake resistant design are adequate. By using the recommended design values, satisfactory performance of the masonry buildings that have been analyzed may be expected when subjected to design intensity earthquakes with respect to both the no-collapse and damage-limitation requirements.
ISCARSAH Symposium "Assessment and strengthening of historical stone masonry constructions subjected to seismic action", 2009
The acknowledgment of the scientific community that the structural safety aspects of constructions belong-ing to the cultural heritage can not be treated according to standard procedures that are fitted for new constructions, is leading to new, specific approaches for assessing their actual structural performances and then for developing new, more appropriate methodologies and design criteria for their repair and strengthen-ing. The basic idea is that the usual, even the most sophisticated, structural design approaches naturally imply a certain level of “over-design”, and this can lead to unacceptable solutions when dealing with “existing structures” (ISO 13822). Over-designing interventions on existing structures could in fact imply in general unacceptable costs and, in the case of the historical heritage, unacceptable losses of cultural (historic, artistic) values. On this respect, the “seismic condition” presents the most delicate implications, as the very extreme resources of the structure , i.e. those connected with resistance mechanisms that are normally neglected and in any case almost impossible to include in structural models, are mobilized. Attempts to offer comprehensive methodologies to tackle such difficulties have been recently made at an international level by the ISCARSAH committee of ICOMOS and, for constructions in seismic areas, by the Italian standardisation bodies (Ministry of Culture and Ministry of Public Works). The consciousness that any calculation imply over-design has as relevant consequence that the formal match between “code requirements” and “formally demonstrated structural performances” can be misleading, and not necessarily required. Assessment is no more considered a more or less sophisticated exercise of analytical/numerical structural models, but an articulated and combined use of structural models, historical informations, surveys and investigations, personal, qualitative judgments (based on past experiences, specific training, comparisons, evaluations of past performances of a constructions) that in a “multidisciplinary” context , ensuring that all the values (economical, social, historic, artistic) of the constructions are taken into account, leads to a final decisions on if and how to intervene. Moreover, safeguarding “cultural values” implies also appropriated selection and design of the intervention materials and technologies. Attention is than paid to the possibilities offered by the traditional solutions and to their possible combinations with innovative ones. The general aspects of the Italian approach that have been outlined, together with some case studies are pre-sented to exemplify these guiding principles and to introduce researches on traditional and innovative tech-niques and methodologies, employed in historical structures, carried out at the University of Padua.