National Civil Protection Organization and technical activities in the 2012 Emilia earthquakes (Italy)

On May 2012, a severe seismic sequence occurred in the central part of the Po Plain (Northern Italy). It was characterized by two main shocks displaying local magnitudes 5.9 (on May 20th) and 5.8 (on May 29th), respectively; the maximum observed intensity was VII–VIII on the MCS scale. The emergency response was coordinated as usual by the Department of Civil Protection (DPC), within the general framework provided by the components and operational structures of the National Civil Protection Service. In addition to the search and rescue and to the population assistance activities, many technical activities were carried out to support the civil protection management of the recovery phase. Among these, mentioning is deserved by: the acquisition and dissemination of the accelerometric data from the National Accelerometric Network and the Seismic Observatory of the Structures, owned and operated by DPC; the evaluation of the liquefaction phenomena; the damage and building safety assessment; the regulations for the seismic safety assessment of industrial buildings, aimed at a rapid re-establishment of the productive activities; the actions undertaken following the evaluations by the Grandi Rischi Commission on the possible evolution of the seismic sequence. All these aspects will be examined under a civil protection perspective.     

On the design and seismic response of RC frame buildings designed with Eurocode 8

Performance-Based Seismic Design is now widely recognized as the pre-eminent seismic design and assessment methodology for building structures. In recognition of this, seismic codes may require that buildings achieve multiple performance objectives such as withstanding moderate, yet frequently occurring earthquakes with minimal structural and non-structural damage, while withstanding severe, but rare earthquakes without collapse and loss of life. These objectives are presumed to be satisfied by some codes if the force-based design procedures are followed. This paper investigates the efficacy of the Eurocode 8 force-based design provisions with respect to RC frame building design and expected seismic performance. Four, eight, and 16-storey moment frame buildings were designed and analyzed using the code modal response spectrum analysis provisions. Non-linear time-history analyses were subsequently performed to determine the simulated seismic response of the structures and to validate the Eurocode 8 force-based designs. The results indicate the design of flexural members in medium-to-long period structures is not significantly influenced by the choice of effective member stiffness; however, calculated interstorey drift demands are significantly affected. This finding was primarily attributed to the code’s enforcement of a minimum spectral ordinate on the design spectrum. Furthermore, design storey forces and interstorey drift demand estimates (and therefore damage), obtained by application of the code force-based design procedure varied substantially from those found through non-linear time-history analysis. Overall, the results suggest that though the Eurocode 8 may yield life-safe designs, the seismic performance of frame buildings of the same type and ductility class can be highly non-uniform.     

On-site structure-specific real-time risk assessment: perspectives from the REAKT project

The availability of computationally powerful and energy-efficient wireless sensing units or WSUs (one or more arranged in the form of a network in the vicinity and/or within a structure of interest) has led to new developments in the field of building and seismic strong motion monitoring. These WSUs can serve several functions. Those of largest earthquake engineering and engineering seismology interest are the recording of ground shaking the building is subjected to, as well as its response, and the capability of running rapid seismic risk analyses on the basis of vulnerability models of the structure, possibly coupled with recorded data. The REAKT project has shed light on a number of prospective applications of the last generation of monitoring devices for seismic risk management of critical structures. These applications refer to real-time and near-real-time risk assessment, that is: earthquake early warning, immediate post-event response evaluations based on recorded shaking, and short-term aftershock risk management for automated building tagging. This paper summarizes these perspectives that, despite still presenting some challenges that may limit readiness to date, have potential for scientific innovation in the field.     

Amplitude dependence of equivalent modal parameters in monitored buildings during earthquake swarms

This paper investigates the dynamic response of three sample buildings belonging to the Seismic Observatory for Structures, the Italian network for the permanent seismic monitoring of strategic structures, managed by the Italian Department of Civil Protection. The case studies cover different building types that could loosely represent the Italian building stock, with a special emphasis on cultural heritage and masonry structures. Observed under a low‐intensity seismic swarm comprising about 30 aftershocks after a main event, the three buildings are analysed through an input–output, model‐driven linear dynamic identification procedure, depicting the relation between the shaking level at the site and the variation of the equivalent structural modal parameters, while keeping into account the effects of soil–structure interaction. Finite element models will be used to investigate one of the case studies and to compare the law of variation of the structural modal parameters with respect to simplified models proposed by technical standards. Copyright © 2017 John Wiley & Sons, Ltd.     

Urban seismic stations: soil–structure interaction assessment by spectral ratio analyses

In this work we present and discuss the results of ambient seismic noise analyses computed at four sites where seismic stations, managed by the INGV (Italian Institute for Geophysics and Vulcanology) and the DPC (Italian Department of Civil Protection), are installed inside buildings. The experiments were performed considering different types of installation: sensor located at the bottom of a school, directly installed on rock (case 1); sensor located at the bottom of a medieval fortress, built on an isolate hill, directly installed on rock (case 2); sensor installed on the foundations of a medieval fortress, built on an isolate hill (case 3); sensor installed on the foundations of a school, built on alluvial deposits (case 4). Since recent works proposed the use of spectral ratio techniques to study the dynamic characterization of buildings, ambient seismic-noise measurements were performed for each site close to the stations (at the base of the structures), at the top of the structures and outside the buildings. In order to check the source of vibrations both horizontal to vertical spectral ratio (HVNR) and standard spectral ratio (SSR) techniques were applied. For all stations the results from ambient seismic noise were compared to those obtained from earthquakes (HVSR). In order to detect preferential directions of amplification, for each site average HVNRs and HVSRs were computed considering one azimuth for each set of 5°. We obtain different results for different types of installation: in cases 1 and 2, where the sensors are directly installed on rock, the vibrations of the structure do not affect the noise measures performed close to the stations, which show flat HVNR in the whole frequency range: in both cases the eigenfrequency of the building is given by the HVNR calculated from the measures performed at the top of the structure. In cases 3 and 4, where the sensors are installed on the foundations of the considered structures, both the amplification peaks between 5 and 9 Hz (case 3) and between 5.5 and 7 Hz (case 4) include the contribution of the free oscillations of the buildings. In particular, in case 4, HVNRs performed outside building highlight possible soil–structure resonance effects in case of an earthquake.     

Simplified seismic sidesway collapse analysis of frame buildings

This paper presents the development and assessment of a simplified procedure for estimating the seismic sidesway collapse margin ratio of building structures. The proposed procedure is based on the development of a robust database of seismic peak displacement responses of nonlinear single‐degree‐of‐freedom systems for various seismic intensities and uses nonlinear static (pushover) analysis without the need for nonlinear time history dynamic analysis. The proposed simplified procedure is assessed by comparing its collapse capacity predictions on 72 different building structures with those obtained by nonlinear incremental dynamic analyses. The proposed simplified procedure offers a simple, yet efficient, computational/analytical tool that is capable of predicting collapse capacities with acceptable accuracy for a wide variety of frame building structures. Copyright © 2013 John Wiley & Sons, Ltd.     

Variable stiffness smart structure systems to mitigate seismic induced building damages

Upgrading noncode conforming buildings to mitigate seismic induced damages is important in moderate to high seismic hazard regions. The damage, can be mitigated by using conventional (e.g. FRP wrapping) and emerging (e.g. smart structures) retrofit techniques. A model for the structure to be retrofitted should include relevant performance indicators. This paper proposes a variable stiffness smart structure device known as the Smart Spring to be integrated on building structures to mitigate seismic induced damage. The variable stiffness capability is of importance to structures that exhibit vertical (e.g. soft storey) irregularities and to meet different performance levels under seismic excitation. To demonstrate the utility of the proposed retrofitting technique, a four‐storey steel building is modelled in MATLAB and appropriate performance indicators are chosen. Various return period seismic hazards are generated from past earthquake event records to predict the structure's performance. The performance improvement because of the retrofitting of building structures using the variable stiffness device is presented. Copyright © 2012 John Wiley & Sons, Ltd.     

基于LoRa的高层结构地震响应和健康监测系统设计实现

随着我国建造行业逐步向智能建造转型升级,高层结构地震响应和健康监测技术所涉及的传感器数目、待处理的数据量以及系统的复杂性都在不断增加。针对高层建筑结构地震响应和健康智能化监测需求,将物联网LoRa扩频通信技术引入到高层结构智能化监测系统中,设计实现基于LoRa的高层结构地震响应和健康监测软硬件平台方案。该系统由多个LoRa终端节点、LoRa网关、OneNET服务器和用户4个部分组成,监测数据通过LoRa网络传输,LoRa网关通过ESP8266模块接入云平台,将采集到的监测数据形成可视化监测界面。经测试,在城市空旷环境下该系统3 km内的丢包率小于8%,可实现高层结构地震响应和健康监测数据远距离、低功耗的可靠传输,帮助用户进行地震作用下振动反应资料的累积、建筑结构的状态评估和设施管理。     

Introspection on improper seismic retrofit of Basilica Santa Maria di Collemaggio after 2009 Italian earthquake

The 2009 L’Aquila, Italy earthquake highlighted the seismic vulnerability of historic masonry building structures due to improper "strengthening" retrofit work that has been done in the last 50 years. Italian seismic standards recommend the use of traditional reinforcement techniques such as replacing the original wooden roof structure with new reinforced concrete (RC) or steel elements, inserting RC tie-beams in the masonry and new RC floors, and using RC jacketing on the shear walls. The L’Aquila earthquake revealed the numerous limitations of these interventions, because they led to increased seismic forces (due to greater additional weight) and to deformation incompatibilities of the incorporated elements with the existing masonry walls. This paper provides a discussion of technical issues pertaining to the seismic retrofit of the Santa Maria di Collemaggio Basilica and in particular, the limitations of the last (2000) retrofit intervention. Considerable damage was caused to the church because of questionable actions and incorrect and improper technical choices.     

Quantitative archaeoseismological investigation of the Great Theatre of Larissa, Greece

Larissa, the capital of Thessaly, is located in the eastern part of Central Greece, at the southern border of a Late Quarternary graben, the Tyrnavos Basin. Palaeoseismological, morphotectonic, and geophysical investigations as well as historical and instrumental records show evidences for seismic activity in this area. Previous investigations documented the occurrence of several moderate to strong earthquakes during Holocene time on active faults with recurrence intervals of a few thousand years. The historical and instrumental records suggest a period of seismic quiescence during the last 400–500 years. The present archaeoseismological research, based on a multidisciplinary approach is devoted to improve the knowledge on past earthquakes, which occurred in the area. This study focuses on damages observed on the walls of the scene building of the Great Theatre of Larissa. The Theatre was built at the beginning of the third century BC and consists of a semicircular auditorium, an almost circular arena and a main scene building. Archaeological and historical investigations document a partial destruction of the theatre during the second to first century BC. Recent excavations show that the building complex after it was repaired suffered additional structural damages, probably from seismic loading. The damages investigated in detail are displacements, rotations and ruptures of numerous blocks at the walls of the scene building. In order to test the earthquake hypothesis as cause of the damages a simplified seismotectonic model of the Tyrnavos Basin and its surroundings was used with a composite earthquake source model to calculate synthetic seismograms at the Larissa site for various earthquake scenarios. Horizontal to vertical seismic ratio (HVSR) measurements in the theatre and its vicinity were used to estimate local site effects. The synthetic seismograms are then used as input accelerations for a finite element model of the walls, which simulates seismically induced in-plane sliding within the walls. Results show that some of the surrounding faults have the potential to produce seismic ground motion that can induce in-plane sliding of blocks. Model calculations were used to constrain the characteristics of the ground acceleration and infer the causative fault and earthquake by comparing the calculated and observed distribution of the displacements of the blocks. Ground motions with a PGA at the site of 0.62–0.82 g, which could be induced by an M 5.8–6.0 earthquake on the nearby Larissa Fault, would be sufficient to explain the damage.     

Performance of the Italian strong motion network during the 2009, L��Aquila seismic sequence (central Italy)

On April 6, 2009, the town of L’Aquila in the Abruzzo region (central Italy) was struck by a seismic event at 01:32 (UTC), of magnitude M_W = 6.3. The mainshock was followed by a long period of intense seismic activity and within seven days after the mainshock there were seven events of magnitude M_W ≥ 5 that occurred from April 6 to April 13. This long seismic sequence was characterized by a complex rupture mechanism that involved two major normal faults of the central Apennines: the Paganica and the Gorzano faults. The strong-motions of the mainshock were recorded by 64 stations of the Italian Strong-motion Network (RAN) operated by the National Civil Protection Department (DPC). Six stations of a local strong-motion array were working in NW L’Aquila suburb area. One of them, located at about 6 km from the Paganica fault surface tip-line, set up in trigger mode, recorded continuously for more than 20 min the mainshock and the aftershocks. Besides the mainshock, the RAN stations recorded in total 78 foreshocks and aftershocks of M_L ≥ 3.5, during the period from January to December 2009. The corresponding waveforms provide the most extensive digital strong ground motion data set ever recorded in Italy. Moreover, the 48 three-component observations of events of magnitude M_W ≥ 5, recorded at a distance less than 15 km from each of the major involved faults, provide a significant increasing of near-field records available for the Italian territory. Six days after the mainshock, the strong-motion dataset, referred to preliminary locations of the events with M_L ≥ 4.0, was made available on the DPC web site () and at the same time it was delivered to the ITACA database (). This dataset has been used by many authors in scientific papers and by engineers, geophysicists and geologists for professional technical works. In this paper, the present-day available strong-motion signals from the L’Aquila sequence and the performance of the Italian strong-motion network in terms of the number and quality of recorded data, the geometry and data transmission system are described. In addition the role of the temporary network that represents an extension of the permanent Italian strong-motion network, supporting the emergency response by civil protection authorities and improving the network coverage has been evaluated.     

基于时变地震损伤模型的多龄期钢框架结构易损性分析

基于时变地震损伤模型提出酸性大气环境作用下多龄期钢框架结构概率地震易损性分析的方法及步骤;考虑服役龄期对钢框架结构抗震性能的影响,分别建立时变概率地震需求模型、时变概率抗震能力模型及时变易损性模型;在概率地震需求分析及概率抗震能力分析的基础上,得到多龄期(20年、30年、40年、50年)钢框架结构的易损性模型及易损性曲线。     

Mixed nonparametric–parametric probabilistic model for earthquake reliability of an inelastic reinforced concrete frame structure

The paper is devoted to the study of uncertainties when studying buildings under seismic loading. These uncertainties are related to the simplifications used when constructing the model (model uncertainties) and to the numerical data needed at the computation stage (data uncertainties). It has been shown in previous papers that nonparametric models are able, in the case of linear dynamics, to deal simultaneously with these two kinds of uncertainties. The paper presents an extension of this kind of model by taking into account a “mixed” approach for concrete frame structures, which uses a nonparametric model for the part of the structure which behaves linearly and a parametric approach for the parts of the structure (plastic hinges) which behave non-linearly. A numerical application is presented in the case of a residential building.     

Archeoseismological study in Salachik,the ancient capital of Crimean Khans

Archeological, archeoseismological, and seismotectonic studies were carried out in Salachik, the ancient capital of the Crimean Khans, on the outskirts of the modern city of Bakhchysarai, Crimea. The following damage and deformations of medieval buildings were observed: tilted building walls, shifted elements of building structures, rotation of fragments of walls and building blocks around the vertical axis, considerable deformations of arch structures, and fissures running through several rows of building blocks. These deformations are of a seismogenic nature. Traces of at least two strong ancient earthquakes were revealed in the medieval monuments of Salachik. Based on analysis of kinematic indicators, it is found that the maximum seismic intensity (VIII ≤ I ₀ ≤ IX points) was due to an earthquake occurred in the west. Based on historical seismologic data, one of the two earthquakes is dated by April 30, 1698. Also, structural damage to buildings in Salachik was caused by Crimean earthquakes in 1927. The findings can be used for a comprehensive assessment of seismic hazards on the Crimean Peninsula.     

Overview of the Italian strong motion database ITACA 1.0

The Italian Strong Motion Database, ITACA, was developed within projects S6 and S4, funded in the framework of the agreements between the Italian Department of Civil Protection (Dipartimento della Protezione Civile, DPC) and the Istituto Nazionale di Geofisica e Vulcanologia (INGV), starting from 2005. The alpha version of the database was released in 2007 and subsequently upgraded to version 1.0 after: (i) including the most recent strong motion data (from 2005 to 2007) recorded in Italy, in addition to the 2008 Parma earthquake, M 5.4, and the M ≥  4.0, 2009 Abruzzo seismic events; (ii) processing the raw strong motion data using an updated procedure; (iii) increasing the number of stations with a measured shear wave velocity profile; (iv) improving the utilities to retrieve time series and ground motion parameters; (v) implementing a tool for selecting time series in agreement with design-response spectra; (vi) compiling detailed station reports containing miscellaneous information such as photo, maps and site parameters; (vii) developing procedures for the automatic generation of station reports and for the updating of the header files. After such improvements, ITACA 1.0 was published at the web site , in 2010. It presently contains 3,955 three-component waveforms, comprising the most complete catalogue of the Italian accelerometric records in the period 1972–2007 (3,562 records) and the strongest events in the period 2008–2009. Records were mainly acquired by DPC through its Accelerometric National Network (RAN) and, in few cases, by local networks and temporary stations or networks. This paper introduces the published version of the Italian Strong Motion database (ITACA version 1.0) together with main improvements and new functionalities.     

A methodology for defining seismic scenario‐structure‐based limit state criteria for rc high‐rise wall buildings using net drift

As a result of population growth and consequent urbanization, the number of high‐rise buildings is rapidly growing worldwide resulting in increased exposure to multiple‐scenario earthquakes and associated risk. The wide range in frequency contents of possible strong ground motions can have an impact on the seismic response, vulnerability and limit states definitions of RC high‐rise wall structures. Motivated by the pressing need to derive more accurate fragility relations to be used in seismic risk assessment and mitigation of such structures, a methodology is proposed to obtain reliable, Seismic Scenario‐Structure‐Based (SSSB) definitions of limit state criteria. A 30‐story wall building, located in a multi‐seismic scenario study region, is utilized to illustrate the methodology. The building is designed following modern codes and then modeled using nonlinear fiber‐based approach. Uncertainty in ground motions is accounted for by the selection of forty real earthquake records representing two seismic scenarios. Seismic scenario‐based building local response at increasing earthquake intensities is mapped using Multi‐Record Incremental Dynamic Analyses (MRIDAs) with a new scalar intensity measure. Net Inter‐Story Drift (NISD) is selected as a global damage measure based on a parametric study involving seven buildings ranging from 20 to 50 stories. This damage measure is used to link local damage events, including shear, to global response under different seismic scenarios. While the study concludes by proposing SSSB limit state criteria for the sample building, the proposed methodology arrives at a reliable definition of limit state criteria for an inventory of RC high‐rise wall buildings under multiple earthquake scenarios. Copyright © 2016 John Wiley & Sons, Ltd.     

The 1708 Manosque earthquake (France): A reading of its archaeological traces as a contribution to estimate the effects on buildings

Archaeological techniques and methodology are used to identify seismic traces and disorders in ancient buildings. Clear evidence could be identified as direct seismic consequences or as communities’ technical answers for repair or reinforcement of buildings in order to reduce their vulnerability. This methodology is called “archaeological reading of buildings.” It is based on the identification of different construction phases, modifications and past events (human actions or natural phenomena) suffered by buildings during their life. The data read from the buildings are successively observed, identified, described, and recorded, following the principal of archaeological stratigraphy, in order to explain the buildings history. The seismic pathologies are identified according to detailed engineering knowledge of the behaviour of buildings during seismic motion. In this case study, our approach is applied to the historical city of Manosque, located in a seismic area along the “Moyenne–Durance” active fault. As a result of historical researches (Quenet G, Baumont D, Scotti O, Levret A, Ann Geophys, 47(2/3):583–595, 2004), many historical documents gave evidence about this earthquake’s effects. Among these documents, was an exceptional one: the record of a survey made in Manosque by bricklayers a few days after the 14th August 1708 shock. This gave us specific information concerning the seismic damage caused in the town of Manosque and was the starting point to validate the method. In the present paper, the archaeological reading of buildings method is illustrated by two specific cases: the Charité building in Manosque and the Sainte-Agathe chapel in Saint-Maime village. The buildings suffered various modifications during many centuries. This complicates the application of the method, however the observations made from the buildings correlate well with the indications deduced from written sources, validating our approach. The study highlights the necessity to cross correlate different field data in the frame of a multidisciplinary approach in order to obtain valuable results concerning details of seismic damage, its approximate dating by architectural chronology and the communities’ reaction in terms of repairs and reinforcement techniques.     

装配式钢混组合结构加固时抗震性能模糊综合评估模型研究

参数化的装配式钢混组合结构建筑信息模型缺少结构信息描述,无法实现装配式钢混组合结构图档的修正和自主更新,对结构构件的损伤评估效果差,抗震加固性能差。据此提出用于装配式钢混组合结构抗震加固的建筑信息模型,模型框架包括建筑设计模型、结构设计模型、结构抗震加固设计和损伤评估;通过结构构件的实体定义、属性定义和关联性定义,全面描述柱、梁、板和墙等钢混组合结构构件的抗震加固性能信息;采用模糊加固评估方法获取精准的结构构建综合损伤指数,评估结构构件的加固等级,提高抗震加固性能。经实验证明,所设计模型得到的结构损伤指数与实际损伤指数的误差低于0.03,说明该模型分析装配式钢混组合结构抗震加固性能准确性较高。     

Earthquake-induced damage detection and localization in masonry structures using smart bricks and Kriging strain reconstruction: A numerical study

The intrinsic vulnerability of masonry structures to seismic events makes structural health monitoring of the utmost importance for the conservation of the built heritage. The development of piezoresistive bricks, also termed smart bricks, is an innovative technology recently proposed by the authors for the monitoring of such structures. Smart bricks exhibit measurable variations in their electrical properties when subjected to external loads or, alternatively, strain self-sensing capabilities. Therefore, the deployment of a network of smart bricks into a masonry structure confers self-diagnostic properties to the host structure. In this light, this paper presents a theoretical investigation on the application of smart bricks to full-scale masonry structures for seismic assessment. This includes the study of the convenience of providing electrical isolation conditions to the sensors, as well as the effectiveness of smart bricks when installed into either new constructions or in pre-existing structures. Secondly, numerical results are presented on the seismic analysis of a three-dimensional masonry building equipped with a network of smart bricks. Finally, in order to map the strain field throughout the structure exploiting the outputs of a limited number of sensors, an interpolation-based strain reconstruction approach is proposed.