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Large parts of Asia, Europe, and the eastern USA have high population concentrations in moderate seismic regions (MSR), where very large earthquakes are rare. With rampant construction in the cities located in MSRs, a relatively moderate earthquake can turn into a catastrophe. Limiting the collapse has been the conventional performance objective for regions with high seismicity. However, this does not necessarily translate into a more desirable target of life-safety under design basis earthquake in MSRs. The present paper investigates the seismic performance of non-ductile reinforced concrete (RC) buildings that were common before the advent of modern design standards, and are found in very large numbers. An analytical model capturing the shear failure is employed using a drift-based limit state material. The results show that a hybrid index captures moderate damage more accurately than the prevalent drift-based index. The paper further shows that while a generic ground motion suite accurately estimates the median fragility, it fails to capture the uncertainty. A 7-story non-ductile RC archetype building was found to be at a collapse prevention risk of 2 × 10–4. The seismic risk deaggregation reveals that seismic risk consistency can be enhanced by explicit specification of the seismic forces for retrofitting. The study shows that the stringent seismic risk targets can be met by non-ductile buildings in MSR, provided they are designed or retrofitted with constraints on strong column weak beam factors. The study will facilitate in developing a scheme for prioritizing and devising the retrofit of pre-modern code and non-ductile deficient buildings. [ABSTRACT FROM AUTHOR]

The seismic response of monopile foundations is a growing area of research as the offshore wind industry expands worldwide, including in earthquake prone regions of the world. This paper presents dynamic centrifuge tests aimed at investigating the dynamic response of monopiles in both dry and saturated sandy soils. The latter case includes soil liquefaction under strong input motions, with measured excess pore pressures indicating liquefaction. The natural frequency of the monopile-soil system is experimentally determined by measuring the response to a sine sweep motion. Strong earthquakes are then applied at this frequency and its harmonics. This paper discusses the response of the monopile in terms of the peak accelerations observed in the dry and saturated tests, as well as using response spectra and amplification ratios. The dynamic bending moments along the pile are also measured to infer the bending moment profile with depth. Finally, two identical monopiles are pushed-over in each of the centrifuge tests to establish the pre and post-earthquake monotonic response, including the lateral stiffness and capacity, which are compared for the dry model tests and the saturated case. [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]

In this paper, the dynamic response of two 21-story buildings was studied to assess the influence of higher modes in their structural performance. While the first building was structured with ductile moment-resisting steel frames and exhibits a global shear-dominated lateral deformation, the second one uses ductile concentrically braced steel frames and has a global bending-type response. Buildings were virtually located in a soft-soil condition of the lake-bed zone in Mexico City. Nonlinear pushover and dynamic analyses were performed through OpenSees on a detailed 3D-model with plasticity spread along the elements. For this purpose, a set of accelerograms recorded during the Mexico Earthquake of September 19, 2017, were selected, and adjusted to represent the actual seismic hazard at the site. A frequency-domain system identification technique was applied to identify the dynamic characteristics of buildings through a moving-window Fourier analysis, that allows for the estimation of the contribution of higher-modes to their overall nonlinear dynamic response. A ratio of the elastic spectral pseudo-accelerations corresponding to the first two vibration modes is proposed to quantitatively anticipate cases and conditions for which the second mode adversely affects the structural performance of upper stories. The discussion includes a comparative study from the lateral global response of the analyzed models. [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]

Seismic losses due to earthquakes have been shown to have significant economic, social and environmental consequences. Over recent years, research to predict potential economic and social impact due to seismic risk has been increasing. Recognizing that the traditional philosophy of life safety design can lead to extensive damage and demolition which has a large environmental cost, incorporating environmental impacts associated with the expected seismic damage over a building's life is a key step as the building industry moves towards both sustainable and seismically resilient design. This paper introduces a framework that uses environmental indicators quantifying losses from seismic response that can then be used to advocate for a change in seismic performance objectives. First, existing literature and previously developed approaches for quantifying potential environmental impact due to seismic damage are summarized. Next, performance based earthquake engineering concepts are used to demonstrate a probabilistic approach to quantify potential environmental impacts using a range of environmental and resource use indicators over the life span of a case study building. In addition, a case study is presented to compare different environmental indicators between a Code Minimum building and the same building redesigned for a higher seismic performance. The majority of the composition of the environmental indicator values are from the inclusion of the non-repairable scenario, and from the repair activities, the majority of the impacts are from damage to drift sensitive components including curtains walls, partitions and elevators. For the Code Minimum building the non-repairable scenario contributes to between 8 to 11% the total seismic cost. For the Stronger Stiffer building, the non-repairable scenario contributes around 3% of the initial impact. Neglecting non-repairable scenarios does significantly reduce the potential environmental impacts when analyzing buildings designed for current code minimum structural standards. [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]

The track structure has an effect on the dynamic characteristics of the bridge structure, which makes the seismic response of the bridge structure complicated. In this paper, an assessment method is proposed to evaluate the seismic risk of bridge structure, including over-limit risk and over-limit scale. Based on a newly proposed simplified model with high accuracy and high computational efficiency, a total of 3000 calculation conditions are analyzed and the sample stability of response is validated to ensure the reliability of the seismic risk analysis. The seismic risks in the longitudinal direction of the track-bridge model are compared with that of the trackless model, and the influence of the constraint effect of China Railway Track System II ballastless track structure on the seismic risk of the structure is obtained. The influence of the number of spans and PGA on track constraints is also revealed. The analysis results, based on a large number of samples, show that although track constraints can reduce the seismic risk of some phenomenon, such as girders' collision, the expected enhancement of longitudinal seismic safety of the system cannot be guaranteed in general, especially when the number of spans is large. However, it is noted that the track constraint can effectively control the over-limit scale of the system, which can reduce the expected repair cost after an earthquake. Therefore, it can be considered that the positive effect of the track constraints is more significant in economy than in structural safety when the bridge is subjected to a longitudinal earthquake excitation. [ABSTRACT FROM AUTHOR]

In this paper a novel approach named Multi Pier Macro MPM method is proposed for seismic analysis of steel moment frames. Based on the model an arbitrary multi-bay and multi-story moment frame is substituted by a single bay braced frame consists of two piers and two braces at each story. Piers are continuous and braces are pinned to piers. Both piers and braces are 1D truss elements. The axial, flexural and shear stiffness of the moment frame are provided by axial behavior of piers and braces. MPM method was benchmarked against four steel moment frames including two mid-rise and two high-rise buildings. The seismic responses of equivalent braced frames including maximum floor displacements and story drifts was compared with original moment frames responses as exact results, by means of Non-linear Static Procedure NSP and Non-linear Response History Analysis NL-RHA. NL-RHA was performed using twelve ground motion records scaled to Maximum Design Earthquake MDE and Maximum Considered Earthquake MCE hazard intensities. The results proved the simplified braced frame is able to estimate the seismic responses of mid and high-rise moment frame buildings with high accuracy meanwhile the analysis time and computational cost were limited remarkably. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of soil–structure interaction and site amplification on the seismic response of one of the towers of the Theodosian walls of Constantinople during the Kocaeli earthquake in 1999, that largely damaged it. The interacting system is first analysed in the frequency domain by the well-known replacement oscillator model, turning out that the effect of soil–structure interaction could be relevant. The complete system is then examined by the direct approach considering non linearity of the behaviour of both the structure and the soil. The failure mechanism detected from where stress and plasticization concentrate into the masonry panels is consistent with the out-of-plane mechanism of one of the tower façades triggered by the reference earthquake. The focus was then set on the effectiveness of some retrofitting interventions, including the lateral disconnection of the embedded sides of the tower from the surrounding soil, the soil treatment by grouted columns and the classical technique for masonry rehabilitation. Even though the latter choice is the most common one, retrofitting interventions concentrated into the soil could be effective as well. Their use should be properly considered when the scope of the intervention is the preservation of cultural heritage. [ABSTRACT FROM AUTHOR]

The study of the seismic response of long bridges under non-uniform seismic excitation date back to the early 80 s. So far, many methods have been developed to estimate the bridge responses under such excitation. Eurocode-8 is considered the first seismic design code that provided a simplified method for linear seismic analysis of long bridges under non-uniform seismic excitation. In this method, earthquake ground motion at each bridge support is decomposed into uniform and relative excitations. Any desired elastic response quantity of bridge for each input is obtained and results are combined using the SRSS combination rule. In this paper, it is shown that the SRSS method leads to very conservative and unrealistic responses. An alternative combination rule is then recommended for response estimation, and random vibration analysis is used to calculate the correlation coefficient between the two mentioned responses. Efficiency evaluation of the proposed method is investigated by Monte Carlo simulation results of nine long bridges with different geometrical and dynamic characteristics. Two simplified mathematical bridge models for longitudinal and transverse directions are developed. Then, a simple mathematical formula for the correlation coefficient is extracted, and its accuracy and performance are evaluated. Finally, it is concluded that the proposed formula is relatively accurate and appears in acceptable results. [ABSTRACT FROM AUTHOR]

Recent Italian earthquakes have shown the seismic vulnerability of many typical historical masonry churches characterized by one nave and wooden roofs. Under transverse earthquake, the nave transverse response of this kind of churches can be influenced by the geometrical and material features. To increase the seismic performance, strengthening interventions aimed to pursue the global box-behavior by the realization of dissipative roof-structure represent a valid strategy, especially to avoid out-of-plane mechanisms. In this way, the roof structure must be able to represent a tool for the damped rocking of the perimeter walls. Cross-laminated timber (CLT) panels with calibrated metal connections have been recently adopted in experimental tests as a valid solution to obtain a roof-diaphragm with ductile behavior, satisfying the conservative restoration criteria at the same time. In this paper, after a description of the numerical approach for the damped rocking mechanism for one nave configuration church, the effectiveness of different CLT based roof-diaphragms in the nave transverse response is investigated for four historical churches. The seismic responses are performed by comparative dynamic nonlinear analyses and the results are shown in terms of displacements and shear actions transferred to the façade. The influence of the geometrical features of the churches on the nave transversal response is deepened by sensitivity analyses with the aim to predict the displacements and shear variations under the same earthquake excitation. [ABSTRACT FROM AUTHOR]

An investigation on seismic response characteristics and modal parameters of a cable-stayed bridge with movable bearings using vibration records obtained from a seismic monitoring system is presented in this paper. The object of this study is the Tokachi cable-stayed bridge, a single plane prestressed cable-stayed bridge that is equipped with moveable spherical frictional plate (SFP). The bridge seismic responses subjected to various levels of earthquake including the 2003 Tokachi Great earthquake were obtained from a permanent seismic monitoring system. The bridge dynamic characteristics that include frequency and damping were estimated by both the time-invariant and time-variant recursive subspace identification methods. The identification results reveal that damping ratios of the low order modes estimated during the largest earthquake can reach more than 10% of the critical damping, which is higher than what usually assumed in the seismic design code. Supplementary damping caused by friction force at the movable SFP bearings was identified as the main source of the large damping, and it was quantified by a modal-based inverse analysis using the sparse regularization method. Results of the analyses confirm the influence of moveable SFP bearings performance with its Coulomb-friction type stick–slip behavior on the dynamic characteristics of the bridge. The bearings remain stuck at smaller excitation causing higher stiffness of the structure and slip during a larger excitation resulting in stiffness reduction. The sliding process induces friction force between contacting surfaces of the SFP bearings which results in the increase of damping as the excitation level increases. The damping, however, does not increase continuously, but becomes steadier after a certain level of excitation. [ABSTRACT FROM AUTHOR]

This paper sets out to explore the different ways in which communities deal with earthquakes. As is well known, the ability to recover from a damaging earthquake varies greatly across the world. The events of 2010 were of course a striking reminder of this, when the death toll from the Haïti earthquake was at least 100,000; in the very different conditions of Chile, a much larger event the same year killed just 525 people. In a narrow sense, much of the difference can be explained in terms of the engineering properties of the physical infrastructure affected; the better it has been designed and constructed to withstand strong ground shaking, the greater the chance that the community affected has of recovering quickly. However, the central thesis of this paper is that the ability of a community to deal with earthquakes involves much more than just technical factors. Seismically resilient buildings and other infrastructure will only be in place when an earthquake strikes if there has been a willingness and ability to devote the necessary resources to building them. Moreover, taking prior steps to limit physical damage is only one part of the process for dealing with earthquakes; providing for immediate post-earthquake needs and for the longer term rebuilding of communities is also important. To pursue these issues further, and how they might affect engineers, I visited four widely differing regions of high seismicity. During this study tour, I examined the societal context in which seismic engineers operate and talked to many people involved in earthquake protection and response. The intention was to identify the ways in which the ability of communities to deal with earthquakes depend on societal factors such as economics, politics and more general cultural dimensions. Based on these investigations, I believe that seismic engineers can contribute more effectively to ensuring successful outcomes after an earthquake strikes if fully aware of these societal factors. We need to look beyond our narrow technical field of providing earthquake resistant facilities and widen our vision to consider the complex systems, both ‘hard’ and ‘soft’, in which those facilities will operate. E. F. Schumacher’s famous book (Schumacher 1973) ‘Small is beautiful’ has the subtitle ‘the study of economics as if people mattered’. I believe that seismic engineering should be practised ‘as if people mattered’. [ABSTRACT FROM AUTHOR]

Despite significant research advances on the seismic response analysis, there is still an urgent need for validation of numerical simulation methods for prediction of earthquake response and damage. In this respect, seismic monitoring networks and proper modelling can further support validation studies, allowing more realistic simulations of what earthquakes can produce. This paper discusses the seismic response of the "Pietro Capuzi" school in Visso, a village located in the Marche region (Italy) that was severely damaged by the 2016–2017 Central Italy earthquake sequence. The school was a two-story masonry structure founded on simple enlargements of its load-bearing walls, partially embedded in the alluvial loose soils of the Nera river. The structure was monitored as a strategic building by the Italian Seismic Observatory of Structures (OSS), which provided acceleration records under both ambient noise and the three mainshocks of the seismic sequence. The evolution of the damage pattern following each one of the three mainshocks was provided by on-site survey integrated by OSS data. Data on the dynamic soil properties was available from the seismic microzonation study of the Visso village and proved useful in the development of a reliable geotechnical model of the subsoil. The equivalent frame (EF) approach was adopted to simulate the nonlinear response of the school building through both fixed-base and compliant-base models, to assess the likely influence of soil–structure interaction on the building performance. The ambient noise records allowed for an accurate calibration of the soil–structure model. The seismic response of the masonry building to the whole sequence of the three mainshocks was then simulated by nonlinear time history analyses by using the horizontal accelerations recorded at the underground floor as input motions. Numerical results are validated against the evidence on structural response in terms of both incremental damage and global shear force–displacement relationships. The comparisons are satisfactory, corroborating the reliability of the compliant-base approach as applied to the EF model and its computational efficiency to simulate the soil–foundation–structure interaction in the case of masonry buildings. [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]

Site effects in consequence of the 2016–2018 Central Italy seismic sequence "marked the fate" of many villages located close to the epicenters along the Apennine chain. Pescara del Tronto, a small settlement located on a mountain slope in the municipality of Arquata del Tronto, (AP) is very representative of such territories since, early after the onset of the seismic sequence, suffered very impressive site effects, including a large seismically-induced debris flow and a high number of small volume landslides. This paper describes the main results of the scientific activities carried out by the authors in this locality in the framework of the unprecedented large-scale Seismic Microzonation project funded by Italian Government in Central Italy for 138 territories. Through an intense field activity, the geological and geomorphologic setting of the study area were revised and updated, including a landslide susceptibility assessment that helped the Italian Department of Civil Protection in the emergency management for temporary housing and, later on, was included in the 3rd Level Seismic Microzonation study implemented by authors while the seismic sequence was still ongoing. A very detailed and reliable subsoil model for this municipality was defined, despite difficulties faced in performing direct and indirect investigations due to the safety restrictions for many areas. The Local Seismic Site response was finally assessed for this locality and the results discussed. A key role in the occurrence of strong site effects into Pescara del Tronto has been played by quaternary deposits having an unexpected heterogeneity under the old village. [ABSTRACT FROM AUTHOR]

According to the United Nations Office for Disaster Risk Reduction cities must take measures to anticipate disasters and mitigate their impact, protecting homes and cultural heritage, minimizing losses due to earthquakes and other threats. After the recent earthquakes in historical city centres, the evaluation of the seismic risk, even in regions of low or moderate seismicity, is imperative, being damage assessment and loss estimation essential for its reduction. In this paper the seismic risk analysis of the residential buildings in the Ciutat Vella District in Valencia, with great historical and architectural value, is presented. The vulnerability of Ciutat Vella has been assessed with the Vulnerability Index Method establishing the seismic quality of the residential buildings according to their structural typology, conservation status, age and geometry; identifying the most vulnerable buildings. Damage probability matrices have been obtained for the deterministic and probabilistic earthquake scenarios, estimating for each of them, the seismic risk in terms of direct social and economic losses, mapping the results using a GIS system tool. Results confirm that the vulnerability of the building stock in Ciutat Vella is high being the seismic risk significant. In the event of an earthquake, many residential buildings included in the Catalogue of Listed Buildings of the Special Protection Plan of Ciutat Vella will be damaged. The detailed analysis of the most vulnerable buildings will provide, in future research works, criteria for intervention to enhance their structural seismic response, safeguarding the architectural heritage and contributing to the reduction of human and material losses. [ABSTRACT FROM AUTHOR]

This paper describes how the earthquake parameters of historical earthquakes have been determined in Europe from macroseismic data by means of the so-called 'Boxer' method, in the frame of the European Commission 2009-2012 Project SHARE (Seismic Hazard Harmonization in Europe). The problems related to the assessment of magnitude are described with more detail; the methodological issues are developed with special reference to the 'stable continental region'. The paper first describes how the coefficients of the Boxer method are determined in five tectonic regions of the European area from the relevant calibration data sets, and discusses the problems dealt with while performing this task. Then it describes how the results have been checked against data different from those used in the previous phase. Finally, the application of the new coefficients to nearly a thousand of European earthquakes before 1900 is described. Stressing that, for the first time in Europe, homogeneous results have been obtained at such a large scale, the final part of the paper is devoted to analyse such results, with special reference to the general trends and to some case-histories. [ABSTRACT FROM AUTHOR]

The seismic Performance-Based Assessment (PBA) of monumental buildings requires to consider safety and conservation objectives, including also the possible presence of artistic assets. In order to face these issues, the case study of the Great Mosque of Algiers is analysed in this paper: in fact, besides to be one of the remaining Almoradiv architecture and the oldest mosque of the city, it is also characterized by the presence of a mihrâb, a decorated arched niche that represents an interesting artistic asset to be included in the PBA. Within this context, particular attention has been paid to the choice of the most reliable modelling strategy for the application of the displacement approach in the PBA procedure, as a function of different possible seismic behaviours. In the case of Great Mosque both the current state of the building and a virtual strengthened condition are analysed. It is worth noting that, while in the current state the seismic behaviour of the asset is well described by a set of macroelements that may be analysed independently (through 2D models), in the second case the strengthening intervention leads to the adoption of a 3D global model (indeed, the roof bracing promotes a 'box-type' behaviour). In the paper, the integrate use of three different modelling strategies of different complexity is discussed: the finite element model, the equivalent frame approach and the macro-block model. The results of nonlinear analyses performed (static and kinematic) constitute the main tool to interpret the seismic response of the asset, perform the PBA and address the choice on the rehabilitation decisions. These latter in this case are mainly affected by the occurrence of too high deformations in local portions of the building, including that in which the artistic asset is located. [ABSTRACT FROM AUTHOR]

According to most of current design standards, the need for high strength and ductility of reinforced concrete frame structures is accomplished utilizing a high amount of transverse reinforcement in beam-column joints. Reinforcement congestion can be overcome by means of Fiber Reinforced Concrete and High Performance Fiber Reinforced Concrete, which are known to improve the structural performance of single structural members or beam-column joints. Through an extended numerical simulation, this paper elaborates the overall benefits of using fiber reinforced concrete materials in critical regions to the seismic behaviour of regular reinforced concrete frame structures. An extensive number of non-linear static and dynamic analyses with distributed plasticity and fibre sections are performed to compare the behaviour of simple reinforced concrete and mixed reinforced concrete/fiber reinforced concrete frames in terms of total base shear and fragility curves and failure mechanisms. Even if execution and technological aspects are beyond the scope of the present work, the use of fiber reinforced concretes in critical regions of mixed frames seems to improve the structural performance of reinforced concrete frames at a global level. [ABSTRACT FROM AUTHOR]

The M = 7.8 Muisne event of April 16, 2016 occurred on Saturday at 18:58:37 local time off-shore of the west coast of northern Ecuador. Several cities in the province of Manabí were directly affected and a state of emergency was declared in six provinces encompassing a total area of 70,000 km. The building stock was severely damaged. 80% of the buildings were destroyed in the city of Pedernales, while several multi-storey reinforced concrete structures totally collapsed in the cities of Manta and Portoviejo. Field observations on the seismic performance of reinforced concrete buildings inspected by the authors are presented in this paper. Also, numerical results from three-dimensional pushover analysis of a representative case study building are discussed. The effect of corrosion and masonry infills, which played a key role in the observed damage, was directly taken into account in the analytical model. [ABSTRACT FROM AUTHOR]

In this paper, we separate the residuals of ground motion prediction equations into different components, calculating the repeatable site-specific ( $$\delta S2S_{s}$$ ), location-specific ( $$\delta L2L_{r}$$ ) and path-specific ( $$\delta P2P_{er}$$ ) correction for the median model. In this way, we can reduce the total standard deviation (sigma) of the ground-motion model by Lanzano et al. (Bull Seismol Soc Am 106(1):73-92, 2016), removing these components and overcome the ergodic assumption. These repeatable terms are empirically estimated using a dataset composed by acceleration waveforms of Italian events mainly occurred in the Po plain and Eastern Alps (Northern Italy), in the time interval 1976-2015. The analysis is carried out on 2241 recordings, from 88 shallow earthquakes recorded by 168 sites. A local model, specifically tailored for Northern Italy, is used as the reference GMPE, which predicts the geometric mean of the horizontal peak ground accelerations and response spectral ordinates in the period range 0.04-4 s. Because most of the propagation paths sampled only once, the path-specific components and the resulting aleatory variability are also calculated from the spatial correlation of residuals, following the approach of Lin et al. (Bull Seismol Soc Am 101(5):2281-2295, 2011). We find a significant reduction of the overall ground motion variability to an extent comparable to what observed from previous studies on empirical and simulated datasets. The estimated median corrections and variance components can be used in probabilistic seismic hazard assessment for a single site and a single path in Northern Italy. As an example, we compute the hazard curves at some sites by means of three different approaches (ergodic, partially non-ergodic and full non-ergodic), in order to quantify the impact of relaxing the ergodic assumption. [ABSTRACT FROM AUTHOR]

This paper presents a reassessment of the seismic intensity estimated for the 2011 Lorca (southeastern Spain) earthquake based on detailed vulnerability data and its comparison with the observed damage. Building and urban data are gathered in selected areas during a field campaign and are completed with office work. The significance of vulnerability modifiers in the final vulnerability distribution is analyzed, and their relation with observed damage trends is explored. A direct application of the vulnerability modifiers is not capable of reproducing the observed damage patterns. A significant increase of vulnerability related to the performance of buildings presenting soft story is required to reach a damage distribution consistent with intensity estimates in the study areas. Accordingly, an intensity increase in certain study zones (as compared to other areas of the city of Lorca) is suggested. Although the approach followed in this study is applied in a city of Spain, it can be extrapolated to other areas where detailed vulnerability assessment is feasible and damage data are available. [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]

The method employed in this study combines large-scale shaking table tests with fully coupled 3D non-linear dynamic analysis to investigate the site response and structural damage mechanisms of laterally spreading site cluster pile foundation systems under weak and strong seismic excitation. The study also aims to verify the applicability of the high-efficiency and universal parallel calculation system method, which involves SolidWorks, HyperMesh, OpenSeesMP, and GiD, with a fully visualized interface operation in geotechnical engineering, based on the test database. The results show that under weak seismic excitation, the acceleration and displacement in the free field and near-pile region are linearly distributed along the burial depth, and the motion of shallow pile foundation is mainly controlled by the inertial effect of the superstructure; while under strong seismic excitation, the displacement in the near-field region is much smaller than the free field showing significant pile pinning effect, and the displacement and acceleration in the near-pile domain are cosine-shaped distributed along the burial depth, with the lateral spreading of site liquefaction intensifying. At the intersection of clay and sand layers, a weak interlayer is present, which affects the structural response. The kinematic effect of the site dominates the response, and the location of vulnerability gradually shifts from the pile bottom to the pile head. [ABSTRACT FROM AUTHOR]

The 2010–2011 Canterbury Earthquake Sequence caused extensive damage to over 6000 residential buildings in Christchurch and highlighted an urgent need to improve the resilience of the housing sector. As a result, the authors have developed the eco-rubber geotechnical seismic isolation (ERGSI) foundation system for new low-rise buildings. It is a cost-effective and sustainable technology that integrates a horizontal geotechnical seismic isolation (GSI) layer—i.e. a deformable seismic energy dissipative filter made of gravel–rubber mixtures (GRMs)—and a flexible rubberised concrete (RuC) raft footing. The present study aims at evaluating the performance of an ideal ERGSI system in dissipating seismic energy and assessing the seismic response of two-storey RC framed structures placed on the ERGSI system. Firstly, results of laboratory investigations are presented and ideal GRM and RuC for use in ERGSI systems are identified. Hence, OpenSees finite-element numerical investigations and spectral acceleration analyses are undertaken for a 900 mm-thick GRM layer with 40% rubber content by volume. Further, time-history dynamic analyses—carried out by SeismoStruct software—are presented and discussed for two ERGSI-isolated RC framed structures having natural period of 0.3 s and 0.5 s. The results obtained for the ERGSI-isolated structures are finally compared with those obtained for two non-isolated framed structures placed on a traditional foundation (i.e. RC footing placed on a compacted gravel layer). This study demonstrates that the seismic demand (i.e. peak acceleration measured at the structure top-floor, lateral deformation at each floor and base shear) on low-rise buildings can be significantly reduced by using ERSGI foundation systems. [ABSTRACT FROM AUTHOR]

Regional earthquake early warning (EEW) alerts and related risk-mitigation actions are often triggered when the expected value of a ground-motion intensity measure (IM), computed from real-time magnitude and source location estimates, exceeds a predefined critical IM threshold. However, the shaking experienced in mid- to high-rise buildings may be significantly different from that on the ground, which could lead to sub-optimal decision-making (i.e., increased occurrences of false and missed EEW alarms) with the aforementioned strategy. This study facilitates an important advancement in EEW decision-support, by developing empirical models that directly relate earthquake source parameters to resulting approximate responses in multistory buildings. The proposed models can leverage real-time earthquake information provided by a regional EEW system, to provide rapid predictions of structure-specific engineering demand parameters that can be used to more accurately determine whether or not an alert is triggered. We use a simplified continuum building model consisting of a flexural/shear beam combination and vary its parameters to capture a wide range of deformation modes in different building types. We analyse the approximate responses for the building model variations, using Italian accelerometric data and corresponding source parameter information from 54 earthquakes. The resulting empirical prediction equations are incorporated in a real-time Bayesian framework that can be used for building-specific EEW applications, such as (1) early warning of floor-shaking sensed by occupants; and (2) elevator control. Finally, we demonstrate the improvement in EEW alert accuracy that can be achieved using the proposed models. [ABSTRACT FROM AUTHOR]

An earthquake with an epicenter offshore of Hualien City in eastern Taiwan occurred at midnight on February 6, 2018. The Richter magnitude (ML) of the earthquake was 6.26 and the seismic intensity ranged up to level VII, the strongest seismic intensity level regulated in Taiwan. Almost all the major damage resulting from this seismic event was occurred near both sides of the Milun Fault, where records from nearby strong motion stations displayed the characteristics of near-fault ground motions. The main seismic damage was the collapse of four buildings with soft bottom stories, one of which resulted in fourteen of the seventeen total fatalities. Comparing the acceleration response spectra with the design response spectra sheds light on the effects of near-fault ground motions on the collapsed buildings. Based on the eventual forms of collapsed buildings, building collapses that have generally led to major casualties in past seismic events around the world can be classified into sit-down, knee-down and lie-down types. In addition to the four collapsed buildings, seismic reconnaissance on other buildings, bridges, ports, and non-structural components have also been conducted. This study explores the issues and challenges arising from the reconnaissance results and thereby enhances learning from the seismic event. [ABSTRACT FROM AUTHOR]

Remarkable damage to non-structural elements and sometimes to structural members was surveyed in buildings retrofitted with dissipative bracing (DB) technologies recently hit by moderate-to-medium amplitude earthquakes. Damage is a consequence of the delayed contribution of protective systems to the seismic response of the buildings, caused by too high activation forces of dissipaters. In view of this, a sizing procedure for DB systems incorporating fluid viscous (FV) spring-dampers is implemented in this study. The procedure provides a simplified version of a recently proposed energy-based design criterion, and an extension of it by including a pre-evaluation of the activation force of the FV devices with respect to the normative Serviceability Design Earthquake (SDE)-related seismic demand. The sizing procedure is applied to the retrofit design of a demonstrative case study, represented by a school built in Italy in the early 1980s. Noticeable seismic vulnerabilities of the above-ground steel structure of the building are assessed in current conditions, highlighting local unsafety conditions of the profiles constituting the reticular steel columns starting from the SDE. A retrofit intervention consisting in the installation of a DB system equipped with FV spring-dampers is presented for the steel structure, designed by applying the proposed sizing method. The final verification time-history analyses confirm the activation of the FV devices at the SDE, and the attainment of the targeted elastic structural response up to the Maximum Considered Earthquake normative level. [ABSTRACT FROM AUTHOR]

A simplified calculation model for the integration of tracks and bridges of multi-span simply supported beam bridge on high-speed railway is proposed by considering the longitudinal connecting effects of adjoining structure. Using this simplified calculation model, the seismic response of multi-span standard simply supported beam bridges of multiple high-speed railways was calculated and compared with the seismic response using the corresponding full-bridge model. Based on the above calculation results, the simplification efficiency and equivalent stiffness of simplified calculation model was studied. Seven earthquake records were selected for calculation, and the growth rates of seismic responses with the increase of number of spans were analyzed in detail. The analysis results show that the seismic response using the simplified calculation model and corresponding full-bridge model are identical with each other; the simplified calculation model greatly reduces the calculation time and the efficiency of reducing calculation time is up to a maximum of 86%. The order of arrangements of interlayer components such as shear teeth and support significantly affects the equivalent stiffness of adjoining structures. The equivalent stiffness of adjoining structures becomes stable with the increase in the number of spans of simply supported beam in adjoining structures. The adjoining structures has an amplification effect on the seismic response of target structures, and the amplification effect becomes stable with the increase in the number of spans of simply supported beam in adjoining structures. Without considering the restraint effect of adjoining structures, the seismic response of multi-span simply supported beam bridge on high-speed railway becomes unsafe, that is, the result is smaller than that of considering adjoining structures. [ABSTRACT FROM AUTHOR]

Over the last two decades, seismic ground motion prediction has been significantly improved thanks to the development of shared, open, worldwide databases (waveform and parametric values). Unlike seismic ground motion, earthquake data recorded in buildings are rarely shared. However, their contribution could be essential for evaluating the performance of structures. Increasing interest in deploying instrumentation in buildings gives hope for new observations, leading to better understanding of behavior. This manuscript presents a flat-file containing information on earthquake responses of instrumented buildings. Herein, we present the structure of the NDE1.0 flat-file containing structural response parameters (i.e. drift ratio, peak top values of acceleration, velocity and displacement, pre- and co-seismic fundamental frequencies) computed for several intensity measures characterizing ground motion (i.e. peak ground values of acceleration, velocity and displacement, spectral values, Arias intensity, strong motion duration, cumulative absolute velocity, destructive potential). The data are from real earthquake recordings collected in buildings over the years. Some building, site and earthquake characteristics are also included (i.e. structural design, shear wave velocity, magnitude, epicentral distance, etc.). This 1.0 version contains 8520 strong motion recordings that correspond to 118 buildings and 2737 events, providing useful information for analyses related to seismic hazard, variability of building responses, structural health monitoring, nonlinear studies, damage prediction, etc. [ABSTRACT FROM AUTHOR]

The seismic performance of three modern unreinforced masonry buildings struck by the earthquake sequence of May 2012 in Emilia (Italy) has been investigated, to define the safety margins and possible critical issues in the seismic design according to the European seismic codes. The selected structures have been redesigned, applying linear and static nonlinear analyses, and verified against collapse according to both Eurocodes 6 and 8 and Italian Norms for Constructions. The design has provided inconsistent results, in particular with the application of Eurocodes, where none of the three buildings fulfilled the safety checks even at very low lateral action, although two of these structures did not attain any visible damage after the events of May 2012. The requirements of the Italian seismic code have provided, at least for static nonlinear analyses, results more in line with the actual seismic response of the buildings. The main issues and some proposals for the improvement of the codified procedures for seismic design of unreinforced masonry buildings are finally discussed. [ABSTRACT FROM AUTHOR]

The non-smooth contact dynamics method was selected to investigate the damage occurred to typical masonry churches (namely Apennine churches) belonging to Central Italy areas affected by the seismic activity started in 2016. The investigated buildings show discontinuous dynamics since the optioned method gave the chance to properly model the temples as multi rigid body systems using the Signorini's impenetrability condition and the dry-friction Coulomb's law, achieving a thoughtful response to ground seismic solicitations. The results provided by the assessment grant an overview of the most common damages and failure mechanisms, giving the guidelines to restoration projects that fully respond to structural needs. [ABSTRACT FROM AUTHOR]

The present research aims to study the influence of the soil–structure interaction (SSI) and existence or absence of masonry infill panels in steel frame structures on the earthquake-induced pounding-involved response of adjacent buildings. The study was further extended to compare the pounding-involved behavior versus the independent behavior of structures without collisions, focusing much on dynamic behavior of single frames. The effect of SSI was analyzed by assuming linear springs and dashpots at the foundation level. The infill panels were modeled using equivalent diagonal compression struts. The steel frames were assumed to have elastic–plastic behavior with 1% linear strain hardening. The dynamic contact approach was utilized to simulate pounding between the adjacent buildings. Nonlinear finite element analysis was performed for two adjacent multi-story structures with four different configurations representing cases that can exist in reality. The seismic response of the studied cases generally emphasized that ignoring the soil flexibility and/or the contribution of the infill panels may significantly alter the response of adjacent structures. This may result in a false expectation of the seismic behavior of buildings exposed to structural pounding under earthquake excitation. [ABSTRACT FROM AUTHOR]

In the aftermath of the Mw 6.0 August 24, 2016 Central Italy earthquake, the authors carried out a reconnaissance survey in the municipality of Amatrice and gathered extensive photographic evidence of damage, with emphasis on 37 reinforced concrete buildings located outside the historical centre. Damage distribution is generally represented by widespread cracking and/or collapse of the masonry infill panels at the lower buildings' stories. Moreover, damage was observed in the columns due to the interaction with masonry infill panels. Starting from the collected information, POST—a mechanics-based damage prediction model—was applied in order to compare predicted damage distribution and damage observed during the field reconnaissance. The comparison shows an overall good agreement between the results of the POST method and the observed damage with a slightly conservative tendency by POST. [ABSTRACT FROM AUTHOR]

Due to the stable hysteretic behavior, buckling-restrained braces (BRB) have been increasingly adopted in reinforced concrete (RC) frame structures to develop a dual structural system. This investigation aims to quantify the seismic behavior of newly-constructed reinforced concrete BRB frames (RC-BRBFs). The force–deformation characteristic of dual RC-BRBFs is firstly presented and the yield displacement is derived using the story shear ratio resisted by BRB system. The seismic design procedure of dual systems for different BRB configurations (including single diagonal, V-type and inverted V-type), is developed using the performance-based plastic design approach by considering BRB postyield behavior, design target drift and global yield mechanism. 126 RC-BRBF structures corresponding to different story numbers, BRB configurations and story shear ratios are designed. The influence of story shear ratios on the design results is analyzed. The seismic response of structures subjected to 22 ground motions is investigated and compared in terms of yield mode, maximum interstory drift ratio, BRB maximum ductility and cumulative ductility, and residual drift ratio. The relationship between actual and design normalized story shear of BRBs is demonstrated and a fitting equation is proposed to quantify the actual story shear ratios. The analytical results of the present study can provide quantified insights to the seismic design of RC-BRBF structures. [ABSTRACT FROM AUTHOR]

On 21st August 2017, an earthquake (ML3.6; MW3.9; Md4.0) 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. [ABSTRACT FROM AUTHOR]

We have analyzed the recently developed pan-European strong motion database, RESORCE-2012: spectral parameters, such as stress drop (stress parameter, Δ σ), anelastic attenuation ( Q), near surface attenuation ( κ ) and site amplification have been estimated from observed strong motion recordings. The selected dataset exhibits a bilinear distance-dependent Q model with average κ value 0.0308 s. Strong regional variations in inelastic attenuation were also observed: frequency-independent Q of 1462 and 601 were estimated for Turkish and Italian data respectively. Due to the strong coupling between Q and κ , the regional variations in Q have strong impact on the estimation of near surface attenuation κ . κ was estimated as 0.0457 and 0.0261 s for Turkey and Italy respectively. Furthermore, a detailed analysis of the variability in estimated κ revealed significant within-station variability. The linear site amplification factors were constrained from residual analysis at each station and site-class type. Using the regional Q model and a site-class specific κ , seismic moments ( M ) and source corner frequencies f were estimated from the site corrected empirical Fourier spectra. Δ σ did not exhibit magnitude dependence. The median Δ σ value was obtained as 5.75 and 5.65 MPa from inverted and database magnitudes respectively. A comparison of response spectra from the stochastic model (derived herein) with that from (regional) ground motion prediction equations (GMPEs) suggests that the presented seismological parameters can be used to represent the corresponding seismological attributes of the regional GMPEs in a host-to-target adjustment framework. The analysis presented herein can be considered as an update of that undertaken for the previous Euro-Mediterranean strong motion database presented by Edwards and Fäh (Geophys J Int 194(2):1190-1202, 2013a). [ABSTRACT FROM AUTHOR]

In low-to-moderate seismicity regions such as metropolitan France, characterized by limited strong-motion records in the magnitude-distance range of interest for seismic hazard assessment, the derivation of empirical ground motion prediction equations (GMPEs) is a major challenge. In this study, we take advantage of the RESORCE-2013 database () that contains uniformly processed records for the Pan-European region including relevant number of French records. After discussing the metadata for French events and stations, we first derive a base-case GMPE that is used to investigate the within-event and between-event residuals. The short-period between-event residuals for French (and Swiss) events show larger variability with respect to larger magnitude events in other regions. We show that the between-event residuals are clearly correlated with the stress parameter and that such larger variability can be explained by accounting for stress-parameter scaling. We derive an empirical scaling of ground motion with stress parameter that is consistent across regions and with the scaling predicted by stochastic GMPEs. This suggests that the scaling of ground motion with stress parameter for a given magnitude is largely region independent whereas the absolute stress parameter values may vary regionally. Based on these results we propose to adopt the scaling model as a function of stress parameter and magnitude by Yenier and Atkinson (Bull Seismol Soc Am 105(4):1989-2009, 2015) by adapting the reference stress parameter to our target regions. By accounting for stress parameter scaling in the GMPE we reduce the between-event variability for French and Swiss small-magnitude events. Finally, we investigate the aleatory variability (σ) of the GMPE and its components (τ, ϕ, ϕ). We propose a heteroscedastic σ model to be used when the stress-parameter scaling is not considered in the GMPEs due to lack of information. If enough information on the stress-parameter is available the adjusted GMPE can be applied using a homoscedastic σ. Despite using small events, the ϕ for French stations is found to be consistent with other studies and confirms the stability of ϕ across different regions and datasets. [ABSTRACT FROM AUTHOR]

On the south flank of the Acropolis of Athens there are two 10-m high columns belonging to the monument of Thrasyllos, free-standing since the third century BC. Obviously they have survived earthquakes for more than 2,300 years responding as natural seismoscopes with their damage 'recording' all strong earthquakes during their long life. Their existence naturally raises the questions of whether their mere survival can contribute to our scientific understanding of the long-term seismicity of Old Athens by addressing the various interrelated aspects of the problem combining earth science, seismology, archaeology, history, and engineering. Starting from the literary survey and the seismotectonic investigation of the region we find that although earthquakes were in the City, rarely causing concern, there is no evidence that Old Athens was ever seriously damaged. However, the historical literary record is incomplete having gaps at long periods of time; the columns, therefore, may be used to enhance our knowledge on the long-term seismicity, not only by estimating the worst-case ground shaking that could topple them-which has not happened yet-but in particular to assess the degree of shaking which was responsible for the damage that can be seen today on them. The decoding of this information is not a straightforward procedure and, in general, does not lead to a unique solution. The main reasons for this is on one hand the non-linearity and the sensitivity of the seismic response of multidrum columns, and on the other the lack of information on the evolution of the damage and the uncertainty on the real cause of it: it is not easy to determine how much of the damage to the columns that can be seen today must be attributed to earthquakes alone and how much of it is due to other reasons. In this research, from the detailed investigation of the current state of the columns, the damage caused by earthquakes was separated from the one caused by rusting of dowels and temperature effects. Back analyses were performed using suitable surrogate ground motions, aiming at determining the worst-case earthquake that could cause the collapse of the columns, and the maximum level of shaking that could cause the observed damage. The numerical analyses were performed using the Distinct Element Method and models that were exact reproductions of the columns based on the available data, while the joint properties were calibrated against ambient and forced vibration measurements. The results are consistent with the seismotectonic analysis and show that the mean response spectrum of the worst-case earthquakes is generally compatible with the response spectrum of EC 8 for the corresponding return period. It is possible, though, that the maximum experienced shaking is less. More information is needed on the real effect of the dowels of the drums to draw conclusions on the latter based on the observed damage. [ABSTRACT FROM AUTHOR]

The marine structures in offshore area, such as composite breakwater, are generally vulnerable to the strong seismic wave propagating through their seabed foundation. There are a lot of failure examples during the strong earthquake events in the world in the past 20 years. However, attention given to the seismic response of marine structures under strong seismic wave is limited. In this study, taking the dynamic Biot's equation ' u − p' as the governing equation for porous seabed foundation, the seismic response of a composite breakwater and its porous seabed foundation under the seismic wave recorded in the Japan 311 off the pacific coast of Tohoku earthquake (M = 9.0) is investigated using a FEM numerical model. The numerical results indicate that the seismic response of composite breakwater is very strong in the earthquake process. The amplification of the input seismic wave occurs both in seabed foundation and composite breakwater; and this amplification is positively related to the buried depth of points. The horizontal seismic response is much strong than the vertical seismic response. The seismic wave induced excess pore pressure and effective stresses in seabed foundation vibrates; the vibration amplitude is also positively related to the buried depth of points. Under strong seismic loading, the surface region of seabed foundation could liquefy. The parametric study shows that the young's modulus of seabed foundation has significant effect on the seismic response of composite breakwater. [ABSTRACT FROM AUTHOR]