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Field Investigation of the Performance of Unreinforced Masonry Building Structures during the June 12, 2017, Lesvos Earthquake in the Aegean Sea
Abstract
On June 12, 2017, at 1528 local time (1228 GMT), an earthquake of magnitude MW ¼ 6.2 occurred, its epicenter in the Aegean
Sea (south of Lesvos Island), approximately 23 km to the north of Izmir’s district of Karaburun. The impact of the earthquake left structures in various states of damage, particularly in the town of Vrissa on Lesvos. The types of damage occurring in the buildings of stone masonry in the town of Vrissa, the damage mechanisms, levels of damage and causes of the damage, as well as the relationship between structural characteristics and damage mechanisms have been evaluated in this paper. It was seen in the field investigations that the heavily damaged, partially collapsed, and totally collapsed buildings were generally nonengineered structures. Additionally, the various limitations and dimensional requirements of the Turkish Earthquake Code had not been applied to the damaged masonry buildings in Vrissa. Lower levels of damage had been sustained in masonry buildings in the earthquakes recorded in Elazığ, Van, and Ayvacık, where peak ground acceleration values of strong ground motions were even higher. This was mainly due to the structural characteristic of the houses of Vrissa that rendered a weak connection between the stone external walls and the internal separating walls of the orthogonal wooden construction on the
upper floors. The length of the unsupported load-bearing stone external wall was over the limit specified by the Turkish Earthquake Code, which was the fundamental factor that increased the destructibility of the Vrissa houses.
... Masonry structures with the oldest construction technology are still preferred today due to easy workmanship, thermal insulation, fire resistance, availability local materials and economic issues (Atmaca et al. 2020b, Preciado et al. 2020, Sisti et al. 2019. It has been observed that masonry structures in rural areas have been heavily damaged by earthquakes throughout history because the vertical load performance of masonry structures is generally superior to the horizontal load (winter and earthquakes) performance (Göçer 2020). ...
The majority of Turkey’s geography is at risk of earthquakes. Within the borders of Turkey, including the two major active faults contain the North Eastern and Eastern Anatolia, earthquake, threatening the safety of life and property. On January 24, 2020, an earthquake of magnitude 6.8 occurred at 8:55 p.m. local time. According to the data obtained from the stations in the region, peak ground acceleration in the east west direction was measured as 0.292 g from the 2308 coded station in Sivrice. It is thought that the earthquake with a magnitude of Mw 6.8 was developed on the Sivrice Puturge segment of the Eastern Anatolian Fault, which is a left lateral strike slip fault, and the tear developed in an area of 50 55 km. Aftershocks ranging from 0.8 to 5.1 Mw occurred following the main shock on the Eastern Anatolian Fault. The earthquake caused severe structural damages in Elazığ and neighboring provinces. As a result of the field investigations carried out in this study, significant damage levels were observed in the buildings since it did not meet the criteria in the earthquake codes. Within the study's scope, the structural damage cases in reinforced concrete and masonry structures were investigated. Many structural deficiencies and mistakes such as non ductile details, poor concrete quality, short columns, strong beams weak columns mechanism, large and heavy overhangs, masonry building damages and inadequate reinforcement arrangements were observed. Requirements of seismic codes are discussed and compared with observed earthquake damage.
06.02.2023 tarihinde, Kahramanmaraş merkezli Mw 7.7 ve Mw 7.6 büyüklüğünde meydana gelen depremlerin etkisiyle onbir ilde binlerce bina yıkılmış ve ağır hasarlar meydana gelmiştir. Bu çalışmada, Antakya Lisesi’nde depremlerin etkisine bağlı oluşan strüktürel hasarlar ve nedenleri değerlendirilmiştir. Mimari ve yapısal özelliklerin tanımlanması, hasar türleri ve görülme sıklığının belirlenmesi, hasar nedenlerinni değerlendirilmesi ve hasar nedenlerinin hasar türlerine göre etkinlik derecesinin ortaya koyulması çalışma sürecinin temel adımlarını oluşturmaktadır. Değerlendirme yöntemi olarak literatür, deprem yönetmeliği ve karşılaştırmalı analiz verileri dikkate alınmıştır. Cephe düzeninde yüksek saydamlık oranına rağmen betonarme düşey hatıl sayesinde yapının toptan göçmediği görülmüştür. Bununla birlikte benzer mimari ve yapısal özelliklere sahip birimin toptan göçme nedeni taşıyıcı duvar örgü sistemindeki düzensizlik ve zayıf harç olabilir.
Through low-cycle reciprocating tests on 11 masonry wall specimens strengthened using reinforced-concrete–masonry composite columns, the effects of the position of the composite column, height-to-width ratio, column reinforcement ratio, and axial load ratio on their load-carrying capacity, stiffness, ductility, and energy dissipation capacity were investigated. It was experimentally found that, by strengthening brick walls with RC–masonry composite columns, the concrete and masonry parts can work together effectively, the failure mode shifts from shear to flexural failure, and the strengthened walls exhibit improved bearing capacity, ductility, and energy dissipation performance compared to unstrengthened masonry walls. It is suggested the composite columns can be placed at the ends of the wall if a strengthening measure is required. For walls with height-to-width ratios greater than 1, placing composite columns in the middle of a wall has little effect on the bearing capacity and stiffness of the wall but can improve the ductility of the wall. The height-to-width ratio is a primary factor influencing the structural performance of masonry walls strengthened using composite columns. A smaller height-to-width ratio leads to higher load-carrying capacity and stiffness but may result in reduced ductility. In comparison, the impact of the column reinforcement ratio and axial load ratio is relatively weaker. The flexural capacity of the masonry wall after strengthening can be obtained using the calculation method for concrete members subjected to a combined action of flexure and compression, in which the compressive strength of the masonry is considered.
Seismic retrofits can significantly reduce the vulnerability of masonry buildings. Multiple seismic retrofit alternatives are often available for a given building. Estimating the cost of each candidate action is essential to selecting and implementing the appropriate seismic retrofit initiatives. This research harnesses the capabilities of various regression models for cost estimation. A dataset from 167 retrofit projects for masonry school buildings was used to develop models. Three main retrofit actions were taken into consideration: shotcrete, steel belt and fiber-reinforced polymer. Various regression methods, including multiple linear regression, ridge regression, lasso regression, and elastic net regression, were applied to develop models that estimate the cost of each of the three retrofit actions based on a set of explanatory variables. Next, the models underwent a reduction process to simplify and increase their prediction precision. In most models, the reduction process eliminated multiple terms and enhanced the model prediction performance. This article identifies the height of the building as the most influential parameter governing retrofit costs. It examines the effect of proxy variables (e.g. lateral area of walls and added lateral strength) on the final retrofit cost by adding them as explanatory variables.
Post-embedding of steel bars into mortar joints of unreinforced masonry walls is a widely used strengthening technique in historic masonry construction. Despite its widespread use, limited research is available on the effectiveness of this technique for improving the bonding performance of post-embedded steel bars. In this study, the bond-slip relationship for bars embedded in mortar joints was investigated. The masonry specimens were built using mortar with a strength of 5 MPa, and then reinforced with 5, 10, 15, and 20 MPa mortar and plain steel bars 6 and 8 mm in diameter, and a series of pull-out tests were performed on these specimens. By analyzing the bond strength between the post-embedded steel bars and brick masonry, the bond failure modes, and the bond-slip curves, a typical bond-slip curve and bonding parameters were obtained. The effects of the mortar strength, steel bar diameter, and bond length on the bond strength were discussed, and a mathematical expression for the bond strength between the post-embedded steel bars and brick masonry was presented. In addition, the relationship between the bond strength and the slip distance of the steel bars was obtained, and the interfacial bond fracture energy was analyzed.
On 30th October 2020, an earthquake of magnitude 6.9 hit the Aegean coasts of Turkey and Greece. The epicentre was some 14 km northeast of Avlakia settlement on Samos Island, and 25 km southwest of Turkish town Seferihisar, Izmir. The destruction the earthquake caused concentrated mainly on the mid-rise RC buildings in certain districts of Izmir city. Among the diverse building typologies affected by the event are the traditional/vernacular hybrid timber-masonry and masonry buildings that are common to Turkey and Greece. This paper summarises and discusses the damage levels and mechanisms observed in these types of buildings, based on an extensive field and remote reconnaissance survey in the affected areas in both countries conducted by the Earthquake Engineering Field Investigation Team (EEFIT) of the United Kingdom Institute of Structural Engineers (IStructE). The observed damage is then discussed in light of the level of maintenance and occupancy status. The collected data are also used to empirically construct fragility curves, to assess whether a small sample can be used to describe the overall performance of the buildings in the area and how these compare to the outcomes of previous studies on comparable building stocks.
An earthquake with a magnitude ranging from Mw = 6.9 (KOERI) to Mw = 7.0 (USGS) struck Samos Island in the Aegean Sea on October 30, 2020, with an epicentre 70 kms from the İzmir city centre in Turkey. The earthquake took place at 14:51 local time (11:51 UTC). The peak ground acceleration (PGA) of this earthquake was recorded to be 0.179 g at the epicentre of the earthquake. This earthquake occurred at a depth of 17.26 km (AFAD (2020) İzmir Earthquake Report, (In Turkish)) and lasted 16 s. The main shock from the earthquake triggered a tsunami that hit the building stocks built near the coast. During the gradual deregulation of COVID-19 pandemic regulations, various events caused considerable damage to the building stock, particularly in the Izmir Seferihisar and Bayraklı regions and resulted in a massive disruption of daily habits. The main shock caused 117 deaths in both Turkey and Greece, and 1632 people were also injured in Turkey. Moreover, several injuries occurred in Greece. A total of 103 buildings collapsed, 700 were severely damaged, 814 buildings were moderately damaged, and 7889 were slightly damaged. The basic aim of this paper is to briefly present the past and present seismotectonic characteristics of the region, present building stock, and former structural conditions before the earthquake, assess structural performance and classify distinguished earthquake-induced failures and damage due to the basin effect.
This study presents an overview of seismic hazard in Bhutan and vulnerability of Bhutanese vernacular constructions derived from damage caused by two earthquakes that occurred in 2009 and 2011. Interpretations of damage and seismically vulnerable features of such constructions are provided from field observations. The taxonomy and vulnerability of all existing Bhutanese buildings are presented using a newly developed classification system. Empirical seismic fragility functions for vernacular stone masonry buildings are constructed using the damage data of 2009 and 2011 earthquakes. The sum of observations highlight that Bhutanese masonry buildings are highly vulnerable even in moderate far-field earthquakes.
On 24th of August 2016 a strong earthquake (Ml 6.0; Mw 6.0) struck Central Italy, causing destruction and about 300 victims. The earthquake was the first in a long-lasting seismic sequence characterized by seven events of magnitude larger than 5.4, with the main event of Mw 6.5 occurring on 30th of October 2016. A macroseismic survey was carried out soon after each damaging shock. In some of the most damaged villages a building-to-building survey was carried out. Assessing the intensity during the campaign in the presence of increasing damage was one of the main problems to be dealt with. In this paper we present the data collected in Amatrice, Accumoli, Arquata del Tronto, and its expanded area called Borgo, after the 24th of August and the 30th of October earthquakes, in order to investigate the damage progression and its influence on the intensity assessment according to the European Macroseismic Scale (EMS-98). This work aims to document the evolution of the damage that was observed during the sequence in the above-mentioned areas, by analysing the behaviour of each vulnerability class, and to contribute to the discussion on the assessment of macroseismic intensity in presence of cumulative damage.
On 21st August 2017, an earthquake (; ; ) struck the municipality of Casamicciola Terme on the island of Ischia, Italy. It was a peculiar earthquake: low magnitude, very superficial (focus depth of about 1.7 km), centered in a high population density area. Despite the island was historically struck by destructive earthquakes during the last centuries, buildings vulnerability in the area was high. Many masonry buildings (main structural typology in Casamicciola Terme and on the island) collapsed or were severely damaged, occasionally exposing the original, dating back to end of nineteenth century, wooden frame that is one of the first examples of code designed anti-seismic structures in Italy. In this study, preliminary data and field observations of the 21st August 2017 Ischia earthquake are given. First, data from the permanent seismic network are used to assess seismic input characteristics and compare them to the known seismic hazard. Building vulnerability is then analyzed via the results of field observations carried out soon after the seismic event, thus providing significant information about quality of materials, construction techniques, structural performance and interpretation of possible damage mechanisms.
Four regions of central Italy were struck by the seismic sequence of the 2016 earthquake in the country: Lazio, Abruzzo, Umbria and Marche. This highlighted the different behaviour of masonry constructions depending on the prevention actions carried out after previous earthquakes. In particular, although damaged, the masonry buildings in the historical centre of Norcia (Umbria region) behaved significantly better than those in other regions. Indeed, the strengthening interventions carried out after the earthquakes of 1971, 1979 and 1997 greatly affected the seismic behaviour of masonry aggregates (contiguous masonry structural units, MSUs) in the historical centre, which sustained limited damage and a low number of collapses. This paper discusses the empirical data on damage collected with respect to 670 MSUs by means of the first level survey form concerning post-earthquake damage, and usability assessments (AeDES). The forms completed for the survey relate to MSUs in the historical centre of Norcia and were produced by the technicians of the Umbria Seismic Risk Office. The analysis shows the correlation between the MSU characteristics of: age of construction and renovation work; type of vertical and horizontal structures; roof types and usability rating; and the damage level and extent thereof detected in vertical structures. The effectiveness of previous strengthening interventions and the analyses of the types of strengthening solution are also discussed. A case study aggregate is analyzed in detail in order to illustrate the importance of strengthening interventions on vertical bearing elements. The strengthening interventions resulted in a sound strategy to strongly reduce losses, even in a very vulnerable centre comprised of old residential masonry aggregates.
This paper presents the results of a damage survey conducted on a wide stock of churches in Central Italy, hit by the August 24, 2016 Amatrice seismic sequence. In the weeks following the mainshock, the authors performed a damage assessment of 196 churches in the area involved by the seismic event, aiming to identify damage mechanisms and calculate damage index for each structure. Churches have similar characteristics within the analyzed area, with typical architectural elements, homogeneous structural types and similar construction materials. A discussion presents the main evidences observed during the survey and, lastly, empirical fragility functions are derived for this specific structural type.
Between August 2016 and January 2017 nine shallow earthquakes ranging from 5.0 and 6.5 of moment magnitude affected Central Italy, involving several municipalities wherein unreinforced masonry buildings are more than three quarters of all constructions. Damage state has been very severe, with sixteen settlements belonging to the municipalities of Amatrice, Arquata del Tronto, Accumoli, Castelsantangelo sul Nera and Norcia experiencing a cumulative European macroseismic scale intensity larger than IX. Ground motion demand in terms of peak ground velocity was approximately two or three times what expected for a 475 years return period while the pseudoacceleration response spectra showed values between once and twice gravity acceleration for the period range typical of two and three storeys unreinforced masonry buildings. Moreover, since October 2016, such large seismic demand acted on structures damaged from previous shocks testifying the effects of damage accumulation, too. The significant shaking alone cannot explain the extremely severe damage of some settlements, with large portions of whole blocks completely collapsed, highlighting the need for investigating the specific vulnerability factors and construction features of unreinforced masonry buildings in the affected area. In fact, although some deficiencies already highlighted in previous Italian earthquakes (e.g. inadequate structural connections) have been surveyed also during this sequence, a marked vulnerability of masonry and its mortar has been noticed, in particular in the area between Amatrice and Arquata del Tronto. On the contrary, the historical constructions in Norcia performed much better, as a result of the 1860 seismic code and of the retrofitting interventions implemented after the different earthquakes occurred in the last two centuries. Finally, a number of demolished and rebuilt constructions performed very well, and this was also the case also of modern hollow clay blockwork buildings that protected not only human life, but also cost of construction and continuity of use.
This paper outlines the seismic vulnerability of rural stone masonry buildings affected by the 2015 Gorkha earthquake sequence. Summary of field observation is presented first and empirical fragility curves are developed from the detailed damage assessment data from 603 villages in central, eastern and western Nepal. Fragility curves are developed on the basis of 665,515 building damage cases collected during the post-earthquake detailed damage assessment campaign conducted by Government of Nepal. Two sets of fragility functions are derived using peak ground acceleration and spectral acceleration at 0.3 s as the intensity measures. The sum of the results highlights that stone masonry buildings in Nepal are highly vulnerable even in the case of low to moderate ground shaking. The results further indicate that in the case of strong to major earthquakes, most of the stone masonry buildings in Nepal would sustain severe damage or collapse.
On October 23 and November 9, 2011, two earthquakes struck the Van province, which is in east Turkey. Masonry buildings in the region are known to have been severely damaged; thus, this paper presents an investigation on the seismic performance of masonry dwellings after the 2011 Van earthquakes. The seismicity of the region and its seismic hazards are considered; a door-to-door reconnaissance study was conducted after these strong earthquakes to examine the seismic response of the masonry structures. Rural regions suffered particularly extensive damage from these earthquakes, and the reasons for the observed damage are complex. Regulations of the current Turkish Earthquake Code for masonry structures are compared with field observations, and the latest and draft versions of the code regarding masonry buildings are evaluated. Approaches to enhancing the seismic behavior of masonry dwellings are discussed. Based on the field investigation, the construction quality and control issues are fundamental factors that affect the performance of masonry dwellings. Hence, out-of-plane and in-plane behaviors contributed to the observed damage.
We apply the stochastic method for finite-faults (Beresnev and Atkinson, 1997, 1998) to simulate strong ground motion acceleration from the 1867 earthquake that devastated the Island of Lesvos in NE Aegean Sea. Recent geological data are taken into account to construct realistic models of the earthquake source, while a first-order approximation of the site effect variation throughout the entire island of Lesvos is achieved following an empirical approach suggested by Wald and Allen (2007). We test several source models including different segments of the Agia Paraskevi fault, which is most probably the seismogenic fault of the 1867 earthquake. Stronger ground motion is predicted in the central part of the island, i.e. around the assumed seismogenic structure. A significant site effect is evident along the eastern coast of Lesvos, where the capital of Mytilene lies, strongly hit by the 1867 earthquake, and around the gulfs of Kalloni and Geras in the south and southeast parts of the island. Synthetic peak ground acceleration values are converted to macroseismic intensities through an empirical relation and discussed in comparison with available reports on the macroseismic effects of the 1867 earthquake.
The 7.8 Mw Gorkha earthquake struck the east of Lamjung in Nepal, followed by a sequence of powerful aftershocks. Chinese Team Six including the authors inspected the seismic damage to civil structures along 10 paths in densely populated areas with a seismic intensity of VII to IX 40 days after the main shock. The damage was categorized according to structure types and described in detail. Several remarks are concluded: powerful aftershocks can significantly affect the failure patterns; geological conditions, structure types and height have great influence on the level of damage; the local risky retrofitting technique needs improvement badly.
The earthquake in Van Province took place at 13.41 (with local time, GMT+3) on October 23, 2011 with a magnitude of 7.2 in Turkey. The earthquake with an approximate rupture duration of 50. s occurred at 43.36 Eastern longitude and 38.75 Northern latitude at a depth of 10-15. km below the surface of the earth, triggering an average displacement of 2 m in Northeast-Southwest direction. With Van's Erciş Town constituting the epicenter, the earthquake was felt in the city center and surrounding villages, along with the nearby provinces of Erzurum, Ağri, Mardin, Diyarbakir, Muş, Bitlis, Iğdir, Kars, Batman, Siirt and their respective towns. According to the data released by Republic of Turkey, Ministry of Environment and Urban Planning, 2288 buildings fully collapsed as a result of the earthquake. Analyzing the structural characteristics of the region, it is observed that urban centers are dominated by RC buildings, while mostly adobe structures prevail in the rural areas. The on-site technical investigations revealed that the damages were caused mostly by faulty concrete production, defects in reinforcement details and the poor quality of workmanship. In the study, impacts of the mentioned earthquake on the structures in the region and the underlying reasons were analyzed, and a number of recommendations were provided to prevent the repetition of similar flaws.
The final publication is available at http://www.sciencedirect.com/science/article/pii/S235271021530019X -
ABSTRACT: Most of New Zealand’s stone unreinforced masonry (URM) building stock was constructed between 1860 and 1910 by early European settlers, with approximately 670 stone URM buildings remaining throughout the country. These buildings are typically classified as earthquake-prone, indicating that they require seismic strengthening in order to avoid demolition as a seismic hazard. Practitioners and industry professionals currently lack knowledge about the traditional construction techniques used for these buildings, and about suitable methods for improving their seismic performance. To address this knowledge gap, research was conducted to classify the constituent materials used in the original construction and to document the mechanical and physical characteristics of these construction materials. Extraction of structural mortar and natural stone samples was undertaken in six buildings that were deemed to be representative of the New Zealand stone URM building stock, and X-Ray Powder Diffraction (XRPD) and petrographical analyses were performed on these samples respectively in order to identify mineral composition and their original source location. In addition, the compressive strength of extracted material samples was determined. A database of New Zealand natural stones that were typically used by the early European settlers in construction, including the source and compressive strength of each stone sub-type, is summarised herein. The presented data is intended to facilitate the selection of compatible materials and suitable techniques for repair and seismic retrofit of vintage stone URM buildings.
This paper addresses field investigations of the performance of masonry buildings during the October 23 (Erciş) and November 9 (Edremit), 2011, Van earthquakes in Turkey. Erciş and Edremit are villages respectively located 90 km and 18 km from the city of Van in Turkey. Ground accelerations and response spectra for these earthquakes are discussed. A total of 28,000 buildings were damaged or collapsed in the city center and surrounding villages after the Erciş earthquake. This number increased to 35,000 after the Edremit earthquake. Almost all masonry buildings were affected in the region. Most of them in the area were constructed of random or coursed stone walls with no reinforcement to support heavy clay tile roofing over wooden logs. A large number of such buildings were heavily damaged or collapsed. Cracking and failure patterns are examined and interpreted according to current provisions for earthquake resistance of masonry structures. From the field investigations, it is shown that damages had several causes, among them site effect, location and length of the fault, and poor construction quality. In addition, the two earthquakes hit the masonry buildings within 17 days, causing progressive damage. A large number of nonengineered masonry buildings completely collapsed or were heavily damaged. Most of those in the affected area were not designed and constructed in accordance with the Turkish Earthquake Resistant Design Code.
In the framework of PERPETUATE, LOG-IDEAH: “LOGic trees for Identification of Damage due to Earthquakes for Architectural Heritage” has been developed as a post-earthquake assessment tool for the evaluation of the global seismic performance of architectural assets (AAs). LOG-IDEAH is an expert system which interprets the seismic damage collected on site by relying on the knowledge of engineers and architects in seismic vulnerability assessment. The present expert system has been set up on logic trees, implemented in answer set programming to encode the recognition process that surveyors proceed to investigate the causes of damage and to evaluate the failures occurring on an AA. LOG-IDEAH, available at (http://perpetuate.cs.bath.ac.uk/), allows sketching AAs, recording the state of damage, uploading GPS referenced images and comparing collapse mechanisms observed on site with collapse mechanisms identified by the system. The seismic damage, which is the minimum data required by LOG-IDEAH, is collected at the level of both structural elements and artistic assets (local level) and interpreted at the level of the AA (global level). The answer set programming applied for the construction of the machine-processable representation, once the input data has been recorded into the web-interface, provides all possible failure modes and related possibilities of occurrence by taking into consideration the reliability level of the collected data. Its capability has been validated by applying LOG-IDEAH to the historic centre of L’Aquila of the 2009 earthquake by pointing out that answer set programming is a valid alternative approach to the existing methods developed to identify the seismic performance of masonry AAs.
Online material: Solution quality classification criteria and moment tensor solution data.
This paper describes the application of the iterative method described in Part I (Cardoso R, Lopes M, Bento, R, Seismic Evaluation of Old Masonry Buildings. Part I: Method Description and Application to a Case Study, Engineering Structures, 2005) to the seismic strengthening design of irregular block masonry structures. The method was applied to an old masonry building from the city of Lisbon, which includes a three-dimensional wood structure braced with diagonal elements, aiming at providing seismic resistance to the building. Three different strengthening solutions were defined, based on the collapse mechanism obtained. This paper presents the analysis performed for each solution and the discussion regarding its qualitatively and quantitatively effects in the seismic structural behaviour: the identification of the expected collapse mechanism after strengthening and the seismic intensity for which it occurs. This is necessary to define the more efficient and economic strengthening strategies.
The paper describes the output of a survey carried out in the district of L’Aquila, Italy, in May 2009 after the April earthquake
and later in January 2010, and the consequent vulnerability assessment completed by the authors. Observations collected on
site regard masonry buildings of the historic centre of L’Aquila and the towns of Paganica and Onna; particular focus was
given to a number of buildings of interest, which better represent two locally recurrent building typologies: the mansion
and the common dwelling. A description of the main structural features and their influence on damage mechanism is provided,
stressing the importance of elements such as wall lay-out, quality of masonry and strengthening interventions. The gathered
information is used as input for the application of the FaMIVE method (D’Ayala and Speranza in Earthq Spectra 19(3):479–509,
2003), whereby feasible collapse mechanisms and the associate failure load factors can be identified. The procedure is briefly
outlined and results are discussed from the point of view of the performance point: push-over curves produced by statistical
elaboration of FaMIVE’s output are compared both with the demand spectra obtained from EC8 and the response spectrum for the
main shock as recorded by the closest station to the town. Conclusions are drawn on the reliability of the FaMIVE method with
respect to its capability of predicting the damage mechanism identified on site.
KeywordsL’Aquila–Seismic vulnerability–Masonry structures–Historic centres
This paper evaluates the performance of masonry buildings during the 20 and 27 December 2007 Bala (Ankara) earthquakes. Bala is a township located 50 km southeast from Ankara city in Turkey. The majority of the buildings in the affected region are built in masonry. Most of masonry buildings were formed with random or coursed stone and mud brick walls without any reinforcement. Many of these buildings were damaged or had collapsed. The cracking and failure patterns of the buildings are examined and interpreted according to current provisions for earthquake resistance of masonry structures. The damages are due to several reasons such as poor construction quality and poor workmanship of the buildings. In addition to these reasons, the two earthquakes hit the buildings within seven days, causing progressive damage.
During the last earthquakes in Turkey, reinforced concrete structures in the cities and masonry structures in the rural part were exposed to damage and failure. Masonry houses such as earthen, brick and stone structures are composed of building blocks with weak inter-binding action which have low tension capacity. Bending and shear forces generate tensile stresses which cannot be well tolerated. In this paper, the performance of masonry structures during recent earthquakes in Turkey is discussed with illustrative photographs taken after earthquakes. The followings are the main weakness in the materials and unreinforced masonry constructions and other reasons for the extensive damage of masonry buildings. Very low tensile and shear strength particularly with poor mortar, brittle behaviour in tension as well as compression, stress concentration at corners of windows and doors, overall unsymmetry in plan and elevation of building, unsymmetry due to imbalance in the sizes and positions of walls and openings in the walls, defects in construction such as use of substandard materials, unfilled joints between bricks, not-plump walls, improper bonding between walls at right angles etc.
Infill and partition walls as nonstructural elements are generally constructed with hollow brick masonry and briquette as single or multilayered vertical walls. The seismic responses of infill walls and reinforced concrete (RC) framed buildings have been investigated with field observations after earthquakes all over the world. This study focuses on the reasons infill and partition walls failed as a result of the October 23, 2011 (Mw=7.2), and November 9, 2011 (Mw=5.7), Van earthquakes in Turkey. In this paper, in-plane, out-of-plane, and combined failure mechanisms of single and multilayered infill walls enclosed within reinforced concrete structures were investigated, and construction rules were suggested. To limit the failure of nonstructural elements enclosed within an RC frame, design and construction requirements should be included in the seismic code by adopting suitable solutions for both in-plane and out-of-plane behavior. This paper will be a reference for future studies that investigate infill wall damage.
In the first quarter of 2017, many seismic events occurred in the Çanakkale region, located on the west edge of the North Anatolian Fault Zone (NAFZ). The number of the shakings with a magnitude greater than four (Mw>4) was 23, and the strongest one, with a magnitude of 5.3 (Mw), occurred three times in this sequence. The tectonic settings and seismicity of the region are outlined briefly, and the recorded strong ground motions are analyzed. Effects of these moderate earthquakes on the regional dwellings are also studied. The earthquake-induced damages are determined after the completion of the sequence, and the observed failure and crack patterns are examined. Finally, the seismic performance of these buildings is compared to those in the Aǧrl and Elazlǧ regions, since the same level of earthquakes hit and damaged regional buildings in these Turkish provinces in the past. In this respect, the comparison of the general characteristics of the traditional dwellings with the identified damages in different regions is the final goal of the presented study.
A major earthquake (Mw=6.3) occurred on the 12th of June 2017 (12:28 GMT) offshore, south of the SE coast of Lesvos Island, at a depth of 13km, in an area characterized by normal faulting with an important strike-slip component in certain cases. Over 900 events of the sequence between 12 and 30 June 2017 were manually analyzed and located, employing an optimized local velocity model. Double-difference relocation revealed seven spatially separated groups of events, forming two linear branches, roughly aligned N130°E, compatible with the strike of known mapped faults along the southern coast of Lesvos Island. Spatiotemporal analysis indicated gradual migration of seismicity towards NW and SE from the margins of the main rupture, while a strong secondary sequence at a separate fault patch SE of the mainshock, oriented NW-SE, was triggered by the largest aftershock (Mw=5.2) that occurred on 17 June. The focal mechanisms of the mainshock (φ=122°, δ=40° and λ=−83°) and of the major aftershocks were determined using regional moment tensor inversion. In most cases normal faulting was revealed with the fault plane oriented in a NW-SE direction, dipping SW, with the exception of the largest aftershock that was characterized by strike-slip faulting. Stress inversion revealed a complex stress field south of Lesvos, related both to normal, in an approximate E-W direction, and strike-slip faulting. All aftershocks outside the main rupture, where gradual seismicity migration was observed, are located within the positive lobes of static stress transfer determined by applying the Coulomb criterion for the mainshock. Stress loading on optimal faults under a strike-slip regime explains the occurrence of the largest aftershock and the seismicity that was triggered at the eastern patch of the rupture zone.
On 12 June 2017 (UTC 12:28:38.26) a magnitude Mw 6.3 earthquake occurred offshore Lesvos Island in SE Aegean Sea, which was widely felt, caused 1 fatality, and partially ruined the village of Vrisa on the south-eastern coast of the island. I invert broad band and strong motion waveforms from regional stations to obtain the source model and the distribution of slip onto the fault plane. The hypocentre is located at a depth of 7 km in the upper crust. The mainshock ruptured a WNW-ESE striking, SW dipping, normal fault, projecting offshore and bounding the Lesvos Basin. The strongest and most aftershocks clustered away from the hypocentre, at the eastern edge of the activated area. This cluster indicates the activation of a different fault segment, exhibiting sinistral strike-slip motions, along a plane striking WNW-ESE. The slip of the mainshock is confined in a single large asperity, WNW from the hypocentre, with dimensions 20 km × 10 km along fault strike and dip, respectively. The average slip of the asperity is ~ 50 cm and the peak slip is ~ 1 m. The rupture propagated unilaterally towards WNW to the coastline of Lesvos island at a relatively high speed (~ 3.1 km/s). The imaged slip model and forward modelling was used to calculate peak ground velocities (PGVs) in the near-field. The damage pattern produced by this earthquake, especially in the village of Vrisa is compatible with the combined effect of rupture directivity, proximity to the slip patch and the fault edge, spectral content of motions, and local site conditions.
Specific architectural elements can be identified in constructions located in regions frequently exposed to earthquakes. These earthquake resistant features were developed empirically by local communities to protect their built-up environment. Research in these traditional earthquake resistant practices, resulting from a local seismic culture, is a relevant and positive approach, since it focuses on the strengths of a system rather than on its weaknesses. Its integration into current vernacular building practices can help to preserve and retrofit surviving in-use examples without prejudice to their identity. This paper presents an overview of the most common techniques traditionally used around the world, based on literature review. Additionally, it identifies the use of these techniques in the Portuguese vernacular heritage in order to contribute for the awareness and strength of the local seismic culture in Portugal.
Since the late 1970s, nonlinear static analysis have had an increasing use in the seismic assessment of existing unreinforced masonry (URM) buildings. Different modeling strategies can be used to evaluate the global seismic response of these buildings, such as the Continuous Constitutive Laws Model (CCLM) and the Equivalent Frame Model (EFM). Despite the CCLM modelling approach seems to be the most suitable at this aim, it needs many input data, that are often quite difficult to be known, and requires a high computational effort. For this reason, the EFM, which is based on strongly simplified hypotheses, is preferred in professional practice, where a small computational burden and a time- and cost-saving structural analysis by using few mechanical parameters is needed. In this paper, a review of its uses and limits is proposed, in order to identify the most critical issues and define its proper use in professional practice when applied to existing URM buildings. As a result, it is highlighted that the EFM can be reasonably used as a first conservative approach for the seismic assessment of existing URM buildings with box behaviour and quite regular opening patterns. Thus, up to now, from this review its use is encouraged in seismic analysis of existing URM buildings after providing them a reduction of their floors and roofs deformability, an adequate wall-to-floor and wall-to-roof connections and a regularization of the opening patterns.
The paper analyzes the seismic vulnerability of the historical complex of “San Francesco” located in Cagli, Marche Region, Italy. It provides both advanced 3D modelling with solid elements and equivalent frame modelling. The building is composed of a church and a monastery used as a lower secondary school, and preservation and maintenance of its structural efficiency are of primary importance. The global structural behaviour and dynamic properties of the compound have been evaluated using the Finite Element Modelling (FEM) technique, where the nonlinear behaviour of masonry has been taken into account by proper constitutive assumptions. A sensitivity analysis is done to evaluate the effect of the choice of the control point on the value of seismic risk index, by varying the stiffness of the floors and the effects of different knowledge levels. The aim of the paper is to emphasize the importance of thorough knowledge of historic buildings in order to understand the real seismic behaviour of a structure, to detect common vulnerability of this type of building, the knowledge of which is necessary to design restorations aimed at improving the seismic behaviour of masonry buildings. Some comparisons with the Equivalent Frame Method (EFM) are also presented.
On April 25, 2015, a major earthquake of moment magnitude Mw 7.8 struck the Gorkha District of Nepal at 11:56 a.m. local time (6:11 a.m. UTC). One major aftershock of Mw 7.3 on May 12, 2015, contributed to the devastation of many villages in mountainous areas nearby the epicenter. The spatial distribution of aftershocks, which extended 150 km to the east of the epicenter, suggests that the rupture propagated from west to east, thus producing severe destruction in Kathmandu, at approximately 80 km southeast of the epicenter. A total of 800,000 buildings were severely damaged or collapsed. A post-earthquake reconnaissance showed that damages in reinforced concrete buildings in urban areas were mostly due to poor construction quality, low concrete strength, non-seismic detailing in beam–column joints, and local site effects. Most of the masonry buildings in the villages nearby main shock epicenter were also affected. This paper presents the recorded accelerograms, acceleration response spectra, and the seismological aspects of the earthquake. Case histories of damaged buildings, the patterns, and the failure mechanisms are discussed in this paper. It is concluded that a majority of the damaged buildings were not designed or constructed properly in accordance with national building codes of Nepal or ACI codes.
The seismic behaviour of masonry churches damaged during the 2009 L'Aquila earthquake is studied in this paper. Four important basilicas are considered in order to derive general conclusions from the damage assessment and the performance analysis. As a general result of the comparison between the post-earthquake survey activity and the structural analyses the possibility of evaluating the seismic safety of churches, and therefore of avoiding destructive damage by means of the design and application of appropriate retrofit interventions, is confirmed. Comparative numerical analyses on a sample of four churches have highlighted another important aspect: the dynamic excitation due to the seismic ground motion activates many vibration modes of the building structure, though all of them are characterised by small participation factors. This fact leads to the following important consequences: the high spectral values of the registered record of the L'Aquila earthquake do not correspond to equivalent high values of base shear; in particular the results showed that in all the examined case studies, the base shear V ratio ranged between 20% and 30% of the church weight. Therefore the appropriate choice of the force reduction factor to be adopted for these monumental buildings is not so large since the real shear force value was significantly smaller than the plateau value of the spectral acceleration provided by Italian Code. Furthermore, the awareness of the activation of many local modes under seismic excitation calls for retrofit interventions which have to "tie up" the building, thus avoiding local failures that are often observed. The final conclusion is that the observation of damage and failures under real experimental actions, like real earthquakes, are a precious means for the advancement of knowledge in the field of seismic engineering.
On October 23, 2011, an earthquake (Mw=7.2) hit the eastern province of Van, Turkey, at local time 13.41 (GMT 10.41). According to records, this was the biggest earthquake after the one in Kocaeli, Marmara, on August 17, 1999, The Van earthquake claimed 604 lives near the epicenter and caused extensive structural damage. Recorded ground accelerations were surprisingly low compared to the structural damage observed within the region and recent Turkish earthquakes. Its peak value was approximately 1.78∈∈m/sn2. The objective of this article is to examine the existing reasons for damages to reinforced-concrete and masonry buildings. Additionally, general characteristics of the Van earthquake, seismo-tectonic characteristics of the region, and evaluation of peak acceleration value are presented. All factors that caused damage and collapse are presented as sections, and the observations are compared to the Turkish Earthquake Code and Turkish Building Code terms.
Recent high-intensity earthquakes, such as those occurred in L’Aquila (2009), Christchurch (2010–2011) and Emilia Romagna (2012), have caused not only a significant death toll and huge economic losses, but also heavy damage to the worldwide cultural heritage. In this paper, earthquake damage to monumental constructions is discussed and the following critical issues affecting the seismic response of historic masonry structures are identified: masonry quality; connections among structural elements; diaphragm flexibility; out-of-plane resistance of masonry walls; structural irregularities; wrong retrofit interventions; and earthquake ground motion characteristics. As damage to artworks has induced invaluable losses from a social, cultural and economic standpoint, a simplified performance-based assessment procedure is proposed on the basis of Italian guidelines for seismic risk mitigation of cultural heritage, in order to support the interpretation of observed damage. This procedure could be used for small-to-medium size artworks such as museum contents, historic archives and libraries, and archaeological elements.
Seismic hazard is commonly assessed by using seismicity records and local geotechnical conditions. It is however important to accurately define the probable seismic sources of the broader study area and assess their seismic potential, as earthquake intensities are expected to increase in the close vicinity of active faults. Although onshore faults are considered more hazardous, due to their immediate proximity to inhabited areas, the offshore fault hazard is considerable too, due to their proximity to the islands. In this paper, the identified seismically active faults are used as main elements of an educational programme in the Lesvos Petrified Forest Geopark to raise public awareness and sensitivity on seismic hazard.
Based on previous failure characteristics of masonry structures under earthquakes, and due to the fact that a considerable number of masonry structures have been built around the world, a strengthening strategy for improving seismic performance of masonry structures is adopted and justified in this paper, namely, the external prestressing technique. The principle of this strategy is to tension the prestressing tendons located on both sides of the walls in order to increase the in-plane shear strength and simultaneously to improve the out-of-plane bending resistance of masonry walls, thus allowing an overall improvement of masonry structures under seismic loadings. In addition, this strategy enables multi-level-prestressing to be applied to the walls at different floors, thus allowing optimized compressive prestress in the structure along the building height. In order to validate the effectiveness of this technique, shaking table model tests were conducted. The experimental results showed that, after introducing vertical prestressing to the walls with the proposed technique, the failure mode of the tested masonry structures was influenced, and the torsional resistance was improved significantly. Furthermore, the prestressing also improved the energy dissipation capacity of the walls and enhanced the overall stiffness of the masonry structure.
This paper reviews the performance of stone masonry buildings during the March 25 and 28, 2004, Askale (Erzurum) earthquakes. Askale is a township located 35 kin from Erzurum city in Turkey. A majority of the buildings in the affected region are built in masonry. Most of the masonry buildings were formed with random or coursed stone walls without any reinforcement supporting heavy clay tile roofing over wooden logs. A large number of such buildings were heavily damaged or collapsed. The cracking and failure patterns of the buildings are examined and interpreted relative to current provisions for earthquake resistance of masonry structures. The damages are due to several reasons such as site effect, location, and length of the fault, and the poor construction quality of the buildings. In addition to these reasons, the two earthquakes hit the buildings within three days, causing progressive damage. Low strength stone masonry buildings with mud mortar are weak against earthquakes, and should be avoided in high seismic zones.
A large number of reinforced concrete buildings were heavily damaged or collapsed during the 7.4 magnitude earthquake that struck northwestern part of Turkey on August 17, 1999. Recorded peak ground accelerations were relatively low (0.3g-0.4g) compared to the magnitude of the structural damage, and the elastic acceleration response spectra from the recorded motions were comparable with the elastic design spectra specified in the current Turkish seismic code. A brief description of seismic code requirements is presented and compared with observed details. Other than the damage caused by liquefaction and poor soil conditions in some regions, major causes for large destruction were due to weaknesses and vulnerability of typical three- to six-story nonductile reinforced concrete buildings and their components to seismic loads. These weaknesses include: reinforced concrete columns with insufficient confinement and lateral reinforcement, 90-degree hooks at the end of column ties, short columns, poor detailing in beam-column joint regions, strong-beam and weak-columns, less infill walls in the first stories leading to soft stories, not having proper moment resisting frame system due to irregular column orientation, and poor quality of construction. Buildings with shear wall components performed well.
The distribution of seismicity, faulting pattern and its effect on local geomorphology is examined for the
islands of Lemnos, Aghios Efstratios, Lesvos, Chios, Samos and Ikaria of north-eastern Aegean Sea, Greece.
The main active faults on each island are described in terms of their geometrical characteristics and geomorphology.
Faults that comply with specific criteria (geological age, effect on relief, their geometrical relationship
to the active stress field) have been characterized as active. We evaluated and reviewed published
information, augmented with new field data for onshore faults, while the effects of faulting on the seafloor
and their probable association with recorded earthquakes were used to determine offshore faulting.
The relation of active faulting to the stress pattern has been examined as well. It is shown that as the deformation
changes gradually from transtensional in the north to extensional in the south, so does the active
faulting pattern. The effect of the westernmost splays of the North Anatolian Fault Zone, the largest of
which is the~300 km long, North Aegean Trough, is profound due to their close vicinity, causing shearing
in good agreement with the modeled principal displacement zone deformation pattern. Faulting in the
area is controlled by the distance from the main dextral principal displacement zones: the northern part of
the area is directly affected by the North Anatolian Fault Zone and its splays, while this effect gradually
weakens in the central and southern areas. The geomorphology responds to this faulting, causing the formation
of fault-parallel gulfs near Lesvos and Lemnos and fault-defined shorelines in the rest of the islands.
Ikaria exhibits a notable fault-controlled tilted topography as the result of footwall uplift.
The March 8, 2010 earthquakes that hit Kovancılar and Palu districts of Elazığ province in Turkey and their impacts on masonry and concrete buildings are studied in this paper. According to United States Geological Survey (USGS), magnitudes of these earthquakes, which caused partial or total collapse in many buildings with life losses, were 6.1 and 5.5, respectively. This paper outlines the seismological aspects of the region, the characteristics of the strong ground motion, the geotechnical characteristics of the region and the structural damages based on site assessments. The structural damage level is observed to be directly proportional with the amount of the insufficient quality in the workmanship and usage of inadequate building materials. If a minimum amount of engineering attention had been paid during the construction stages, most of the existing buildings could have sustained the earthquakes without considerable damage.
This paper evaluates the failures of masonry and adobe buildings during the June 23, 2011, Maden (Elazig) earthquake. Maden is a township approximately 80 km away from Elazig city in Turkey. The magnitude of the earthquake was announced as M-L. = 5.3 by the Earthquake Division of the Turkish Disaster and Emergency Management Agency (DEMA). Most of masonry and adobe buildings in Maden and the neighboring settlements had been damaged severely at this moderate earthquake. In this paper, reasons of damages and failures of these structures which are lack of engineering services were examined and explained in detail.
An earthquake with a magnitude of ML = 5.8 has occurred in Kovancılar County of Elazığ, on March 8, 2010. Many structures have been damaged severely or demolished at this moderate earthquake that occurred on East Anatolia Fault zone. The most important reason for damages and collapses of these structures is the lack of engineering services, in other words, not being constructed properly with respect to the available building codes. In this study, damages of various structures (adobe, masonry, hımış, and reinforced concrete structures, and minarets) have been assessed in Okçular and the vicinity villages, where the earthquake damage emerged severely.
The dynamic response of masonry stone buildings during the July 2, 2004, Doğubayazıt (Ağrı) earthquake, Doğubayazıt is a township of about 35 km from Ağrı city in Turkey, is discussed. A majority of the buildings have been built as masonry in the affected region. Most of the masonry buildings were formed with random or coursed stone walls without any reinforcement and heavy clay tile roofing supported on wooden logs. A large number of such buildings were heavily damaged or collapsed. The cracking and failure patterns of the buildings have been examined and explained in detail. The damages are due to several reasons such as site effect, location and length of the fault, and the poor quality of the buildings.
An earthquake sequence struck the province of L'Aquila central Italy leaving 305 dead, about 1,500 injured, and 29,000 homeless. Hundreds of low-intensity events occurred between January and March, 2009. The mainshock took place on April 6, 2009, and its epicenter was located at about 6 km southwest of L'Aquila town; three stronger aftershocks happened on April 7 and 9, 2009. This paper focuses on actual performance of older and more recently constructed building structures during the earthquake sequence. After the main seismological characteristics of the sequence are described, the most significant observed damages are analyzed and associated with theoretical failure modes for both reinforced concrete and unreinforced masonry buildings. Since older masonry structures were more seriously damaged, the effects of the earthquake are described with more emphasis to ordinary masonry and cultural heritage buildings churches, palaces, and castles. In conclusion, a number of lessons may be learned from the L'Aquila earthquake sequence. Several features are highlighted and some proposals are given to upgrade the current methods of structural analysis, as well as the existing codes.
This paper describes a method developed to evaluate the seismic performance of old masonry buildings, which allows identifying the expected structural collapse mechanism of the structure. The collapse mechanism is identified by the accumulation of several damaged structural elements in specific points of the structure. The methodology allows simulating the non-linear behaviour of masonry buildings by making use of an iterative procedure, where the structure is changed at each step according to the cracking, yielding or collapse of structural elements at the previous steps. The method was applied to an old masonry building from the city of Lisbon that includes a three-dimensional timber structure enclosed in masonry walls aimed at providing seismic resistance. Discussion is made regarding the advantages of the iterative procedure for the identification of the expected structural collapse mechanism of old masonry buildings. The method limitations will also be discussed.
The Greek database of seismogenic sources (Gredass) version 2.0.0: A compilation of potential seismogenic sources (Mw > 5.5) in the Aegean region
- R Caputo
- S Pavlides
Literary traces of the old Turkish being in the Greek Islands
- Berbercan M. T.
Lesvos earthquake Mw 6
- E E Lekkas
- V E Skourtsos
- A Antoniou
- Emmanuel
Building damage induced by the 2017 June 12 Mw 6.3 Lesvos (North Aegean Sea Greece) earthquake and application of the European macroseismic scale 1998
- S E Mavroulis
- N I Andreadakis
- Spyrou