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Seismic risk estimation for urban building clusters is essential when developing regional seismic resilience models. A masonry structure is a type of building with a large stock, broad applicability, and simplified construction technology. The traditional seismic intensity measures and fuzzy quantification of structural vulnerability levels result in low accuracy in estimating and predicting seismic damage to masonry structure clusters. This paper proposes a method for evaluating bivariate seismic intensity measure. Nonlinear dynamic and spectral analyses were conducted on real acceleration records monitored by ten stations during the Wenchuan earthquake in Sichuan, China, on May 12, 2008. The outdated seismic vulnerability level of masonry structures is updated, and an optimized structural seismic risk model based on the seismic damage database of 2407 masonry structures in Dujiangyan city under the influence of the Wenchuan earthquake is established. An innovative seismic risk membership index algorithm was developed, and a vulnerability curve was generated for masonry structures considering multiple risk membership indices. An improved seismic risk index calculation function is proposed using the proposed updated vulnerability level, and the seismic risk index curve and stripe model of typical urban masonry building clusters are established. According to the field investigation of the actual structures in Dujiangyan city affected by the Wenchuan earthquake, the typical failure features and disaster mechanism of masonry structures are reported and analysed, and measures and methods to improve and enhance the seismic capacity of such buildings are proposed. The developed seismic risk model for urban masonry structures can contribute positively to the development of relatively accurate seismic resilience models for urban buildings and can improve the accuracy of seismic risk estimation for masonry structures. [ABSTRACT FROM AUTHOR]

Barcelona is in an area of low- to medium-seismicity and its earthquake vulnerability and risk has been assessed in different studies over the last 20 years. Most of these works have developed vulnerability models for the representative building classes of the city, trying to capture their main characteristics, and have been mostly represented through fragility curves. However, due to the lack of data for historical earthquake losses in the city, it has not been possible to validate, nor calibrate, any of these vulnerability models. In the absence of earthquake loss data, the objective of this paper is to compare the earthquake risk results of Barcelona, using common hazard and exposure datasets and different sets of vulnerability functions from previous studies to see how they rank compared with other locations with similar studies but more complete historical loss data. The results show large differences between the analysed vulnerability datasets, with some results that in our view tend to overestimate earthquake risk in Barcelona, and also allow identifying critical aspects that require future research. [ABSTRACT FROM AUTHOR]

On December 29, 2020, nine months after the March Mw 5.4 Zagreb earthquake and amidst the COVID-19 lockdown, a devastating Mw 6.4 earthquake struck near the town of Petrinja, about 50 km SE from the country's capital Zagreb. It was preceded by the Mw 4.9 foreshock from the day before. The main shock claimed 7 fatalities and caused widespread damage. Historical centers of nearby cities with invaluable heritage buildings were significantly affected as were the many residential buildings, built mainly of unreinforced masonry. Damage was observed as far as 60 km from the epicenter. This paper summarizes the seismological aspects of the Mw 6.4 Petrinja earthquake, the emergency response and the main impacts to people and buildings. The description and findings are based on the field observations and a series of post-earthquake activities led by the team of the Faculty of Civil Engineering, University of Zagreb. Typical damage to buildings and usability data are presented with examples based on 50,000 inspection results. By far the most affected were the unreinforced masonry buildings, followed by confined masonry, whereas reinforced concrete buildings were the least affected. The total direct and indirect losses are estimated to 4.8 billion EUR. The provided information represents a useful basis and impetus for improving emergency action and long-term disaster reduction plans in other regions with similar building exposure and seismotectonic settings. [ABSTRACT FROM AUTHOR]

This paper documents performance of cast-in-place reinforced concrete (RC) buildings in the Durrës municipality during Albania earthquake of November 26, 2019 (MW 6.4). Both mid- and high-rise RC buildings were affected by the earthquake, experiencing structural and/or non-structural damage and even collapse in some cases. The authors performed a reconnaissance study after the earthquake and were involved in seismic assessment of buildings in the affected area. Besides the observations related to physical damage of RC buildings, the paper also presents results of a statistical analysis of damaged RC buildings in the Durrës municipality. The discussion in the paper is focused on damage patterns and failure mechanisms that are relevant for the seismic response of RC structures. Most common damage pattern observed after the earthquakes was related to masonry infill walls, which experienced damage and failure in some cases, and affected the performance of adjacent RC columns due to the infill/frame interaction. Taller RC framed buildings (10 storeys and higher) were expected to have RC shear walls; however, these walls were reportedly absent in the damaged buildings of this type. In some cases, masonry infill walls (instead of RC shear walls) were used in the elevator shaft areas, which resulted in inadequate seismic performance. A case study has been presented to illustrate seismic behaviour of mid-rise and high-rise cast-in-place RC buildings in the November 2019 earthquake, and is based on post-earthquake field observations and a detailed seismic assessment of two earthquake-damaged buildings. Finally, relevant lessons and recommendations are presented in light of the observed performance of RC buildings. [ABSTRACT FROM AUTHOR]

The response of a two-storey RC school building in the town of Argostoli, Cephalonia Island, Greece, during the seismic sequence of January and February 2014, is examined. The structure was built following an older generation of seismic codes dating from the 1950s, which provide limited strength and ductility against lateral loads. Despite the severity of ground shaking and the two successive events, the building suffered relatively minor damage, like most of the RC buildings in the town. Following a short presentation of some basic seismological, structural and geotechnical aspects of the seismic sequence, the paper focuses on the seismic performance of the structure at hand. To this end, a series of detailed non-linear static and time-history dynamic analyses are reported, which highlight the interplay of soil, foundation and superstructure in modifying the seismic demand. It is demonstrated that SSI had an unexpectedly important (detrimental) role in the behaviour of the structure, increasing its natural period by about 25% and aggravating ductility demand in almost all columns, despite the moderately soft soil conditions (average VS = 180 m/s). The results shed light on the seismic performance of the building and help drawing conclusions on the engineering effects of the 2014 Cephalonia earthquake sequence. [ABSTRACT FROM AUTHOR]

Summary: The aim of this paper is to demonstrate the efficiency of a low-cost and sustainable timber-based energy dissipation system with recentering ability, which can be used as a seismic isolation system or a tuned mass damper for the seismic protection of structures in developing or developed countries. The system, defined as Dovetail with SPrings (Dove-SP), utilizes the attractive properties of timber to store CO2, thus reducing the carbon footprint of the existing energy dissipation systems: It comprises two timber slabs that are designed to slide against each other in a motion that is restrained by a dovetail sliding joint. Two sliding interfaces that allow this sliding motion at an attractively low friction coefficient are experimentally investigated: A PVC sand-wich (PVC-s) sliding interface, comprising a thin layer of sand that is sand-wiched between two PVC layers and a timber sand-wich sliding interface consisting of a thin layer of sand encapsulated between two beech timber surfaces. A set of low-cost steel springs is designed and installed on both sides of the dovetail joint to recenter the structure back to its original position after the end of an earthquake ground motion excitation. A novel, low-cost and deformable wood material fabricated from delignified balsa wood is used to reduce the pounding effects before the activation of the steel springs. The seismic behavior and the recentering ability of the novel timber-based energy dissipation system subjected to an ensemble of recorded earthquake ground motion excitations was experimentally investigated through a large-scale shaking table investigation at ETH Zurich. [ABSTRACT FROM AUTHOR]

On October 30, 2020 14:51 (UTC), a moment magnitude (M) 7.0 (USGS, EMSC) earthquake occurred in the Aegean Sea. This paper presents the reconnaissance findings regarding the site effects on recorded strong ground motion intensities and duration, along with the resulting induced-structural damage in Izmir Bay and Samos Island, respectively. In all rock records, relatively high intensity long period rock spectral accelerations were observed in the mid to long period range of 0.5–1.5 s, which are attributed to the source, more specifically, to the slower rupture-mechanism of the event. These rich spectral intensities were further amplified by soil site effects and soil-superstructure resonance, leading to two to six times amplified overall responses and prolonged seismic shaking durations, more pronounced in Bayrakli and other Izmir Bay sites in Turkey. However, these amplified and prolonged excitations are still below design basis earthquake levels, which addresses the lack of proper structural design and construction deficiencies, as the underlying causes for the collapse to heavy damage performance of 795 buildings. On the other hand, although located only about 10 km from the rupture (22 km from the epicenter) and within the near fault zone, the town of Vathy on Samos Island (Greece) was rather lightly affected by the earthquake, with relatively few collapsed or heavily damaged buildings, partially attributed to the low height/low weight of structures in the area. However, a concentration of damage in low-rise buildings in Ano Vathy hill is considered indicative of a combination of coupled valley and topography effects on the strong motion. This event once again addressed the need to develop region-specific zonation and provisions, when more general code practices are proven to be inadequate to assess these extreme site effects. [ABSTRACT FROM AUTHOR]

This paper proposes a multi-platform simulation method for the seismic performance assessment of masonry infilled reinforced concrete (RC) frames, especially for those that, due to inadequate reinforcing details, tend to undergo shear failure during an earthquake. The multi-platform method is based on a micro–macro modeling approach in which a detailed finite element model of the RC frame is incorporated with a strut model of the infill wall. It exploits the strut model to increase its computational efficiency and the finite element model based on the modified compression field theory to capture the nonlinear behaviour of the RC frame. The proposed method is validated against previously tested frames subjected to lateral loads, and its advantages over the conventional strut models are demonstrated through both quasi-static and dynamic analyses. [ABSTRACT FROM AUTHOR]

Two strong earthquakes hit Thessaly region on March 3rd, 2021 (Mw = 6.3) and on March 4th, 2021 (Mw = 6.1). The epicentres of the earthquakes were located at approximately 23 and 29 km respectively NW of Larissa, one of the most populous cities in Greece. Several aftershocks followed thereafter. Although no injuries were recorded, several structures suffered significant damage close to the epicentre, while some others collapsed. Approximately 300 residents of the village of Damasi were transferred to temporary settlements and tents. The event occurred during the COVID19 lockdown and created significant stress and disruption to residents. This paper focuses on the earthquake swarm itself as well as the damages observed in residential buildings, schools, and churches in the earthquake-stricken region. The earthquakes mainly impacted low-rise domestic masonry buildings, while the more modern reinforced concrete structures built following the recent seismic regulations were almost unaffected. The typology of buildings in the region, together with photographs demonstrating the extent of damage are presented herein. Despite the rather satisfactory performance of modern buildings in recent earthquakes in Greece, the preliminary investigations from the Thessaly Earthquakes showed that there is still a significant level of vulnerability in existing masonry building stock constructed using traditional methods and materials. This issue could re-emerge in future earthquakes striking other rural areas of Greece, something that needs to be addressed systematically in the future. [ABSTRACT FROM AUTHOR]

Confined masonry buildings are common structural systems in many seismic-prone regions of the world. According to the building code provisions, an appropriate continuous tie system should be provided in these buildings to bind the structural elements together and stop separation and disintegration of these elements under ground shaking. Since usually prescriptive design provisions with minimum calculations are used for constructing confined masonry buildings, investigating their performance in real seismic events is of great importance. In this paper observations made on the performance of confined masonry buildings during the destructive Sarpole Zahab, Iran, earthquake of November 12, 2017 are reported. The earthquake had caused different types of damage in both the structural and non-structural elements of the buildings. Damages were found to be primarily due to large structural irregularities and poor workmanship. Nonetheless, it was noted that those buildings with no significant irregularities, in the construction of which all the code's main provisions had been followed, survived the earthquake and did not experience partial or total collapse. It is suggested that in the taller, two or three storey buildings, with the aim of enhancing the lateral deformation capacity of the load bearing walls, some modifications on the dimensions and reinforcement detailing of the vertical tie elements, particularly those located at the corners of the buildings, to be carried out. In addition, as it has been repeatedly observed in the past earthquakes that after the partial or total collapse of the load bearing walls the tie-beams and tie-columns have served as a secondary gravity load-resisting system and prevented collapse of floor and roof slabs, it is suggested that the adequacy of the current prescriptive detailing of the tie system in acting as a temporary secondary load-bearing system to be verified. [ABSTRACT FROM AUTHOR]

The existing precast reinforced concrete structures not specifically designed against earthquakes have proved to be very sensitive to seismic demands. After the lesson learnt from the Emilia earthquake of May 2012, causing many collapses and severe damage, reliable seismic design criteria have been established for the design of new precast structures and for the strengthening of the existing ones. Despite this, a large percentage of the existing precast buildings in the Italian territories actually has not been object of interventions and remains in an unsafe condition with regard to the seismic actions. In this context, the methods for a rapid seismic assessment can be very helpful both to estimate the current safety level of large building stocks and to plan the necessary strengthening interventions, possibly at the large scale of an industrial area. To this aim, the paper proposes the PRESSAFE-disp (PRecast Existing Structure Seismic Assessment by Fast Evaluation-displacements) method, useful for the fast evaluation of the fragility curves of precast structures. The damage criteria, applicable both to structural elements and non-structural cladding elements on the perimeter, have been selected in order to capture the damage mechanisms observed during the building inspections conducted by the authors in the aftermath of the 2012 Emilia earthquakes. The method allows a comprehensive explanation of the seismic in-plane behaviour of existing precast RC buildings and could be effectively adopted, for example, in earthquake loss estimations and seismic risk assessments of large Italian industrial areas, as well as of wide seismic-prone territories of the Mediterranean area. [ABSTRACT FROM AUTHOR]

In May 2012, two seismic events hit the Emilia-Romagna Region, in Northern Italy. The earthquakes caused collapses and damage to traditional vernacular building heritage, highlighting its seismic high vulnerability. The paper presents a wide collection of damage and collapses observed in the aftermath field inspections on 22 historical vernacular buildings. It was noted that few recurring structural typologies are present in the area hit by earthquake and buildings of the same typology show similar damage mechanisms. Then, with the main goal to identify the most typical damage affecting similar structures, the building stock has been subdivided in different categories based on building plan distribution and intended use. The principal collapse causes, based both on in-field observations and analyses, performed on local and global finite element models, can be ascribed to poor connections between orthogonal walls, lack of effective connections between floor elements and walls, excessive flexibility of floor diaphragms and high slenderness of vertical elements. The outcomes in the present paper allow identifying the vernacular building typologies most vulnerable to earthquake and can help to plan the future retrofitting strategies for vernacular heritage. [ABSTRACT FROM AUTHOR]

The seismic assessment of the vulnerability of existing public structures, especially school buildings, is a crucial issue in seismic prone countries. Recently, several national and regional programs and activities have focussed on the mitigation of Italian public buildings. They promote the scheduling of public buildings' structural safety assessment and, when needed, the design and execution of strengthening interventions. Nevertheless, the three strong earthquakes that occurred in the last decade in Italy, Abruzzo (2009), Emilia (2012), and Central Italy (2016), confirmed the vulnerability of school buildings and the social importance of their quick re-opening after a damaging earthquake. In the present paper, the activities carried out on 1514 school building structures in the aftermath of the 2016 Central Italy earthquake sequence are reported and analysed. According to survey data collected by post-earthquake usability inspections, the paper analyses the school buildings characteristics, damage level and extent to structural and non-structural components as well as the correlation between seismic intensity and observed damage. [ABSTRACT FROM AUTHOR]

At 03:56 local time on November 26, 2019, an earthquake with a Mw = 6.4 struck western part of Albania. The duration of the tremor lasted less than 50 s and was felt largely also in Albania's capital Tirana, and in places as far away more than 300 km northeast of the epicenter. It caused damage to many public and residential buildings in districts of Durres, Tirana, Lezha, Shkodra, Diver, Berat and surrounding areas. This paper describes rapid visual assessment of the damaged buildings (169 in total) in affected areas by IZIIS teams' inspection of damaged buildings. Severe damages were identified in structural and non-structural elements as a result of inconsistent application of recent knowledge in design, construction and quality control of earthquake resistant structures. Structural errors in design and construction as well as inappropriate quality of built-in materials have been observed. Such results from the rapid damage assessment leads to the necessity of taking specific measures as detailed engineering inspection of vital structures as a basis of definition corresponding technical solutions for repair and strengthening with aim of restoring their operational mode. Last but not least, the biggest effect of earthquake damage was observed in non-structural elements which made the structures not-usable for citizens of the earthquake region. [ABSTRACT FROM AUTHOR]

This paper highlights the principal features of the Mw5.4 Zagreb earthquake. Located within the city limits at a depth of 10 km, the earthquake generated a peak ground acceleration of more than 0.2 g and a maximum spectral acceleration of about 0.6 g at 0.1 s in the historic downtown area. The situation was particularly challenging since the event occurred amid a partial Covid-19 lockdown at temperatures close to 0 °C, emphasizing the extensive and complex vulnerability of the local communities and individuals. 27 people were reported severely injured, one of which later died. The surprisingly high economic costs, needed to achieve a full reconstruction of damaged buildings and infrastructure in the affected area, are currently evaluated at more than 10B euros. Description of the organization of the emergency response in the first days and the observed damage to buildings is given with typical examples. The focus is on the performance of older masonry residential and cultural heritage buildings in the historic downtown, their inspection and evaluation of damage to structural and non-structural components. This information provides the basis for understanding of the negative impacts and clarifies the overall context identifying the enablers and barriers to the still ongoing recovery process. It also helps to increase the awareness of the seismic vulnerability of European cities with similar construction practices. [ABSTRACT FROM AUTHOR]

By comparing damage and loss predictions with those observed for a 22-storey steel building with eccentrically based frames (EBF) that underwent the Canterbury earthquakes, this paper gauges the performance and explores the benefits of applying the PEER performance-based earthquake engineering assessment procedure. The study shows that steel EBF repair costs are significantly affected by the work required to remove and reinstate non-structural elements in order to access the steel structure. It is therefore concluded that the location of non-structural elements relative to structural elements should be considered in the seismic design of new buildings and within loss assessment procedures. Two retrofit and/or rehabilitation options are considered for the building; improving the deformation capacity of drywall partitions, and re-detailing the exterior cladding connections to better accommodate structural deformations. The findings show that, for the specific building, improving the drywall partitions should lead to a reduction in expected annual losses whereas the use of improved detailing for the precast concrete cladding would not. This suggests a general strategy for cost-effective decisions might be to focus on increasing the performance of the most vulnerable components (plasterboard partition walls, in this case). An examination of the potential effects of aftershocks to the selection of cost-effective options adds support to this conclusion. Aftershocks are found to increase the predicted losses by around 10%, emphasizing the need to consider aftershocks when assessing expected annual losses due to earthquakes. [ABSTRACT FROM AUTHOR]

The companion paper by Rota and Rosti (Bull Earthq Eng, 2017) illustrates a methodology for comparing PSH results with historical macroseismic observations at different scales, in terms of mean damage. This paper presents examples of application of the methodology, at the different considered scales, to the South-East quarter of France. This moderate seismicity region is characterised by a long history of civilization, which makes macroseismic observations available for a long time span, although they are highly approximated measures of the seismic action and they are affected by significant uncertainties. The first scale of application presented is at a single site, i.e. the city of Annecy. This example shows that, despite the seismic history of this city is characterised by a significant number of macroseismic observations spanning over a long time period, they mostly consist of very low intensity values and hence the comparison at a single site is not very meaningful. Therefore, the comparison is carried out on a set of seven aggregated sites, well distributed in the region of interest, providing interesting results and suggesting the opportunity of extending the comparison at an even larger scale. The comparison at the regional scale also allows some interesting observations, although it is obviously able to only provide general (average) indications on the PSH results. These comparisons were aimed at showing the applicability of the proposed methodology, pointing out advantages and drawbacks of the different application scales. [ABSTRACT FROM AUTHOR]

An earthquake of MW = 6.5 occurred on May 24, 2014, at 12:25 h local time (09:25 GMT), its epicenter in the Aegean Sea, 25 km north of Gökçeada. The effect of the earthquake produced the most damage in the rural houses of Gökçeada. This paper describes the evaluations made through onsite field observations of the damages inflicted on the structures of thirty rural houses in the Tepeköy settlement connected to Gökçeada. An evaluation was made of the types of damage, the mechanisms of damage and the causes of the damage sustained by these houses, which all had similar structural characteristics but different plan typologies and suffered varying levels of damage. The damage observed in Gökçeada was classified using the catalogue of mechanisms originally developed for the failure mechanisms identification and vulnerability evaluation procedure. The general types of damage were cracks in the loadbearing external walls and corners, diagonal cracks starting from the corners of doors and windows, vertical out-of-plane displacement of external walls, out-of-plane fragmentation or disintegration and collapse of external wall and partial collapse of loadbearing internal walls, ruptures in the outer surfaces of loadbearing external walls, partial collapse of roof structure, partial collapse of hearth and chimney sections, rupture or flaking of window and door lintels. The causes of the general damage may be cited as an irregular bonding system, weak mortar, stone block formation, stone block size, absence of tie beams, corners weakly connected, weak connection of wall-roof system, week connection of wall-floor system, and different internal wall systems. The levels of damage and the mechanisms of damage vary depending upon the number of causes of the damage, the particulars of the layout, and some structural properties. In terms of the characteristics of the layout, an increase in unsupported loadbearing wall lengths led to more destructive damage mechanisms in the houses. In terms of structural characteristics, the construction of the internal wall system with timber on the upper floors, and with stone material on the lower floors was a major factor in increasing the level of damage and determining its type and mechanism. [ABSTRACT FROM AUTHOR]

Residual risk exists in our buildings even if they were designed in conformance with modern codes of practice. Various approaches have been implemented or proposed in the last decade for setting risk-based performance requirements for seismic design of building structures. However, there is insufficient consideration about the aggregated risk for society, which could be significant especially for a densely populated metropolitan city. This paper introduces a rational and universal approach for evaluating the adequacy of structural safety requirements by comparing societal risk functions based on probabilistic loss assessment with a proposed regulatory requirement that aims to limit the mortality rate to "as low as reasonably practicable (ALARP)". The proposed approach is then applied to Melbourne, Australia, in a case study, which shows that the earthquake fatality risk for the society appears to be unacceptable. The outcome can be used for justification of a seismic retrofitting policy or a required change of the design code level. The proposed scheme is also applicable to other natural hazards and for safety engineering applications generally. [ABSTRACT FROM AUTHOR]

The assessment of maximum displacement demand is a crucial point in the design of seismic isolating systems, in particular when the non linear behaviour of devices is modeled through visco-elastic equivalent schemes, as common in the design practice. Several phenomena influence the maximum demand assessment, among which the torsional and earthquake directionality effects can be of great impact. International codes use some formulations which allow to consider torsional effects, while the impact of the other phenomena is commonly assessed through time-history analyses. In this paper an innovative design method is developed based on an exact linear elastic formulation with response spectrum, which keeps in count both torsional and directivity effects considering natural and accidental eccentricity and by using the CQC3 (Menun and Der Kiureghian in Earthq Spectra 153–163, 1998. 10.1193/1.1586025) as directional combination rule. The method models the seismic action through the response spectra of a set of natural recorded ground motions, properly oriented along their principal axes to assess the correct ratio between the horizontal components of spectral accelerations; thus accounting for the site-specific earthquake source, without the need to perform time-history analyses. A specific formalization of the dynamic problem is presented to emphasize the parameters which more affects the response (e.g. torsional factor, eccentricity, geometrical aspect ratio) and simplify its interpretation. Results obtained on two case studies are compared with time-history analyses to show the effectiveness of the procedure. [ABSTRACT FROM AUTHOR]

This paper focuses on the structural performance of existing masonry and reinforced concrete bridges which were surveyed in the aftermath of the 2016 Central Italy earthquakes. Typical bridge vulnerabilities are first reviewed, as they provide a reference for the response of the bridges that were damaged by the 2016 earthquake swarm. Case studies are then discussed and preliminary numerical analyses are carried out to interpret the observed failure modes. In general, all surveyed masonry bridges experienced some extent of damage, particularly when built with poor-quality materials and subjected to geotechnical-induced effects. However, they offered a robust response in terms of collapse prevention. The majority of existing reinforced concrete bridges, although designed primarily for gravity loads, exhibited acceptable performance; however, local damage due to the poor maintenance of the structural systems was observed, which affected primarily the non-structural components of the bridges. [ABSTRACT FROM AUTHOR]

Non-structural elements represent most of the total construction cost of typical buildings. A significant portion of the total losses in recent earthquakes worldwide, has been attributed to damage to non-structural elements. Damage to non-structural elements occurs at low levels of ground shaking, and can significantly affect the post-earthquake functionality of buildings. However, in Europe, limited prescriptions are provided in the codes for seismic design of non-structural elements and this may partially explain why it is so common for these elements to perform poorly during earthquakes. This paper describes the observed damage to non-structural elements following the 2016 Central Italy earthquake. The most commonly damaged elements were partition walls, ceiling systems, non-structural vaults, chimneys, and storage racks. As a result, it was highlighted the need to introduce seismic regulations devoted to improving the seismic performance of non-structural elements and to reduce the associated economic losses, loss of functionality, and potential threats to life safety. [ABSTRACT FROM AUTHOR]

The slab spatial composite effect plays a significant role in the seismic behaviour of composite frame structures. In this work, the influence of the slab spatial composite effect on the dynamic behaviour of composite frame structures was numerically studied. The self-developed fibre beam–column element program COMPONA-MARC was used to establish models considering and neglecting the slab spatial composite effect for nonlinear static analysis and elastic–plastic time history analysis under various seismic inputs. The maximum roof displacement, inter-storey drift ratio, normalised displacement indices, deformation mechanism, and failure mode were considered to investigate the structural performance. Comparisons indicated that, despite the contributions of the slab spatial composite effect to the structural lateral strength and stiffness, considering this effect may produce more unsafe results. On one hand, it reduces the fundamental natural vibration period and amplifies the effect of seismic excitation; on the other hand, it changes the structural deformation mechanism and failure mode. The influence of slab spatial composite effect on strong column–weak beam mechanism in different storey drift direction angles is also investigated in the paper. [ABSTRACT FROM AUTHOR]

Historical earthquakes in developing countries, particularly in South America, have caused devastating effects in essential buildings, such as hospitals. As a result, some structural retrofits and new designs of essential facilities in South American countries have concentrated on increasing the seismic design forces beyond what is normally required by building codes. This increased-strength approach can lead to quasi-elastic structural response during earthquakes with much larger induced floor accelerations than expected from code-designed structures. In critical structures, sub-par performance of critical non-structural elements, such as medical equipment in a hospital, due to high-induced floor accelerations can have consequences as devastating as structural failures. Passive seismic protection systems, such as seismic isolation, provide a practical means of controlling seismic demand and are now common in developed countries. However, the applications of protection systems have been far fewer in developing countries due to economic considerations and lack of technical expertise. This paper presents the experimental and numerical studies supporting the development of a novel low-cost sustainable protection system incorporating recycled automobile tires for isolating designated floors or rooms in essential buildings in developing countries. The main innovation of the proposed floor isolation system is the geometric arrangement of the rubber tires that allows isolation from both, horizontal and vertical floor accelerations. Horizontal and vertical cyclic testing conducted on tire specimens are first described followed by the development of a numerical model able to reproduce the experimental results. Finally, an existing case-study hospital in Ecuador is considered for evaluating numerically the seismic performance of the proposed floor isolation system. [ABSTRACT FROM AUTHOR]

The earthquake sequence started on May $$20$$ th 2012 in Emilia (Italy) affected a region where masonry constructions represent a large part of the existing building stock and the construction of new modern masonry buildings is a common practice. The paper is focused on the performance of common architectural configurations, typical for residential or business use. The large majority of old masonry buildings is made of fired clay bricks. The seismic performance of these buildings is particularly interesting since major past earthquakes in Italy affected areas with mainly stone masonry structures. Apart from examples showing systematic or peculiar structural deficiencies governing the vulnerability of several buildings, the overall seismic performance of these structures to repeated shaking, with PGA as large as 0.25-0.3 g was rather good, despite the major part of them were only conceived for carrying vertical loads. In fact, seismic design is mandatory in the area only since 2003. Modern low-rise masonry buildings erected after this date and incorporating seismic design and proper detailing resulted in most cases practically undamaged. The examples reported in the paper allow an evaluation of the superior performance of seismically designed modern masonry buildings in comparison to older ones. [ABSTRACT FROM AUTHOR]

In this paper economic seismic risk analysis of API 5L buried steel gas pipelines is carried out through incremental dynamic analysis using an ensemble of 20 ground motion records. Multiple performance limit states for buried steel pipelines are proposed. Fragility curves of 15 pipeline models of various diameter to thickness (D/t) ratios, burial depth to diameter (H/D) ratios, assumed soil conditions and steel grades are plotted for damage states corresponding to the defined limit states. Expected global economic loss of 1 km length of the pipelines for a given peak ground velocity is obtained using the fragility curves, a pipeline repair ratio as well as costs of leakage repairing and break-induced pipe replacement. The mean annual frequency of exceedance of loss for the investigated pipelines is calculated using a seismic hazard curve and the expected annual loss (EAL) is obtained. It is concluded that in case of the pipelines with the D/t ratio greater than 39.9, the probabilities of failure for a given return period increase with increasing D/t ratio. It is obtained that the probabilities of failure for a given return period increase with increasing H/D ratio and shear modulus of the soil (Gs). The results show that the probabilities of failure decrease with increasing steel grade of the pipes. It is found that for a given return period, the global economic loss increases for an increase in the D/t, H/D and Gs values. The results show that EAL of the pipelines decreases with increasing steel grade of the pipes and decreasing D/t ratio, H/D ratio as well as Gs value. It is obtained that frequency of exceedance of a given loss value increases with an increase in D/t, H/D and Gs values. It is noteworthy that the obtained results are valid only for Tehran, and the pipe and soil characteristics used in the study. [ABSTRACT FROM AUTHOR]

For important facilities, such as hospitals or schools, advanced seismic risk assessment methodologies have been developed and are now available for use by owners and facility managers. These include seismic hazard analysis coupled with structural and non-structural response and damage analyses leading to a final consequence analysis that provides indications of performance measures, which are often referred to as decision variables. Typical decision variables are repair costs, probability of collapse of the entire building and downtime. These decision variables do not provide specific information regarding the likelihood of individual rooms to remain functional after an earthquake. For the case of a hospital, for example, information regarding the functionality of specific critical rooms (e.g. operating or emergency rooms) could influence major design/retrofit decisions by the owner or facility manager. The main objective of this paper is to present, through a case study hospital building in Italy, a methodology for assessing the loss of functionality of individual rooms in critical facilities following an earthquake event. The methodology includes all the aspects that are usually considered individually in seismic risk assessment, such as ground motion selection for probabilistic seismic hazard analysis, structural performance of the building, and the performance of non-structural elements that can affect the functionality of selected rooms. [ABSTRACT FROM AUTHOR]

On Wednesday 11th May 2011 at 6:47 pm (local time) a magnitude 5.1 Mw earthquake occurred 6 km northeast of Lorca with a depth of around 5 km. As a consequence of the shallow depth and the small epicentral distance, important damage was produced in several masonry constructions and even led to the collapse of one of them. Pieces of the facades of several buildings fell down onto the sidewalk, being one of the reasons for the killing of a total of 9 people. The objective of this paper is to describe and analyze the failure patterns observed in reinforced concrete frame buildings with masonry infill walls ranging from 3 to 8 floors in height. Structural as well as non-structural masonry walls suffered important damage that led to redistributions of forces causing in some cases the failure of columns. The importance of the interaction between the structural frames and the infill panels is analyzed by means of non-linear Finite Element Models. The resulting load levels are compared with the member capacities and the changes of the mechanical properties during the seismic event are described and discussed. In the light of the results obtained the observed failure patterns are explained. Some comments are stated concerning the adequacy of the numerical models that are usually used during the design phase for the seismic analysis. [ABSTRACT FROM AUTHOR]

This paper addresses the structural damage to the main buildings of the cities of Reggiolo and Carpi after the primary earthquake shocks on May 20th and 29th, 2012, in Emilia Romagna. The damage survey, performed via form-based methods, highlights the different seismic behaviour of several types of buildings, especially those having historical features, and the consequences of the damage in terms of costs. Moreover, an analysis of some failure mechanisms activated in Reggiolo enables the evaluation of the local peak ground acceleration, due to the soil amplification. [ABSTRACT FROM AUTHOR]

Urban systems are characterized by very complex interactions. After an earthquake, a wide variety of services, networks and urban facilities may be unavailable to the public during the system failure and recovery processes, thereby causing disruptions in the basic social needs of the affected area. After a disaster, communities face several challenges. For example, the lack of education may impose population migrations, or malfunctions in the electricity distribution system can produce electrical power outages of varying duration with respect to time and space, which generates consequences in the water distribution system, transportation, communications, etc. A methodology called the Disruption index (DI), based on graph theory, includes these multiple interdependencies. It has been developed to estimate the dysfunction of some fundamental dimensions of urban systems on a broad level, starting with the physical damages directly suffered by the exposed assets, proceeding to the impacts that each node has on the functional performance of the nodes depending on them, until reaching the top node. This paper presents the fundamental theory to support the DI concept. The DI provides the likely impacts and consequences of an earthquake in an urban area to fulfill hazard mitigation and provide civil protection agencies and local and state governments with a new decision-making instrument to reduce or prevent severe and recurrent impacts. The DI concept can also be extended to other natural and man-made disasters and may be used as a tool for optimizing the resources of the system components. [ABSTRACT FROM AUTHOR]

Due to the increased need of storage, larger and higher structures are being built all over the world, thus requiring a more careful evaluation of the mechanical performance of their foundation deposits both in terms of bearing capacity and compressibility behaviour. The design of such structures and their serviceability and stability is largely governed by the effects of the dynamic loading conditions principally because of their significantly elevated risk in seismic prone zones. In this paper, numerical analyses using an advanced constitutive model, able to account for the initial soil structure and its progressive degradation, have been performed to investigate the seismic response of a silo foundation built on structured clays. The proposed analyses involve the use of a fully-coupled finite element approach. For the dynamic simulations, three different input motions have been selected form earthquake databases according to the seismic hazard study of the specific site. The results of the silo dynamic response are illustrated in terms of signal amplification, permanent excess pore water pressures, accumulated displacements and structure induced degradation during and after the seismic loading. The dynamic behaviour of the footing indicates that extreme earthquake events can induce large destructuration in natural clays, leading to ground settlements up to twice the observed ones under static loads, which need to be properly accounted for in the design. This suggests that there are significant advantages in using advanced models which recognise the existence of initial soil structure and its subsequent damage due to the applied dynamic loads. [ABSTRACT FROM AUTHOR]