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The seismic design of steel systems recently experienced profound changes and progress; in Europe, the research on this topic is very prolific in terms of importance and number of results achieved, even pushed by the recent process of the updating of Eurocode 8. The paper analyzes and discusses the scientific literature on the subject produced approximately over the last twenty years, focusing on both recent research and findings on traditional steel systems and innovative structural types and solutions. The review of the state of the art suggested that most of the authors are now concerned about the numerous criticisms widely encountered in the design of traditional systems according to current Eurocode 8, as well as the difficulty of the application of the relevant detailing rules. The scientific community is also aware of the need to include specific codified design procedures for innovative and promising structural types. Further investigations are needed to deepen the design of moderate-ductile systems and to extend the seismic European prequalification of beam-to-column joints to further typologies. [ABSTRACT FROM AUTHOR]

The importance of non-structural elements on the seismic performance of buildings is now widely recognized. A building cannot achieve a life-safety or continuous functionality performance after an earthquake if all its non-structural elements are damaged and/or out of function. Suspended non-structural elements, such as piping and mechanical services, play a crucial role in maintaining life-safety and functionality of a building after an earthquake. The importance of non-structural elements for the seismic performance of buildings have prompted the development of both force-based and displacement-based seismic design methodologies that can be applied to suspended non-structural elements. This paper focuses on appraising force-based and displacement-based seismic design methodologies available in Europe for suspended non-structural elements by comparing fragility functions for a case-study suspended piping trapeze restraint installation layout located in a mid-to-high seismic zone in Italy. The aim of this study is to determine if the seismic design methodologies available for suspended non-structural elements are capable of producing archetypes that achieve a life-safety performance objective for a design level earthquake (return period of 475 years) and maintain a reasonable performance, in terms of life-safety, for other earthquake intensity levels. Advantages and disadvantages of these methodologies are also highlighted. [ABSTRACT FROM AUTHOR]

Current bridge codes in the US, Europe, and China specify vehicular collision loads for the design of piers. However, the performance of piers designed according to current codes in the three countries or regions is unknown yet. This paper presents a performance evaluation of concrete-filled steel tubular (CFST) piers subjected to vehicle collision. Before the evaluation, bridge specimens with a single CFST pier were designed in accordance with current bridge and structural codes in the three countries or regions, respectively. Then, a detailed finite-element (FE) model for simulating a truck collision with a CFST pier was developed and validated. By comparison with seven simplified FE models, the detailed FE model was further confirmed to be employed for the evaluation. In the evaluation, the effects of current codes in the three countries or regions, whether or not the vehicular collision load is considered, two pier heights (i.e., 6 and 12 m), two truck weights (i.e., 20 and 40 tons), and three impact speeds (i.e., 60, 100, and 140 km/h) on the performance of CFST piers were investigated. The evaluation results indicated that when a CFST pier in seismic zones is designed to resist vehicle collision according to current codes in the US and China, it only needs to meet the requirements of seismic design without additional consideration of the vehicular collision load. Moreover, a preliminary application condition should be added for the vehicular collision load specified by the current bridge code in Europe, that is, when the truck weight is more than 20 tons and/or the pier height is lower than 12 m. [ABSTRACT FROM AUTHOR]

In spite of the names of “building attachments” and “secondary elements” usually given to nonstructural components and equipment, they are far from being secondary in importance. In the worst case of critical facilities, the failure of equipment strongly impacts on the postearthquake functionality, causing the loss of essential services or businesses. Such considerations highlight the need for a seismic qualification of equipment as the essential means to demonstrate its adequacy to perform the required function during the expected earthquake event. In this paper, the authors deal with a new approach to the problem of seismic qualification, in which the seismic demand posed to the component is defined in terms of equipment seismic levels (ESLs), whereas its inherent seismic capacity is classified in terms of equipment qualification categories. The determination of the ESL, which is the subject of this paper, has to satisfy the requirements prescribed by the codes for the seismic design of equipment. A comparative study of the current seismic codes in the USA and in Europe is hence carried out in order to critically assess their provisions and to develop a methodology that can be implemented straightforwardly also by designers not having expertise in the field of earthquake engineering. [ABSTRACT FROM PUBLISHER]

This paper proposes a macro‐model for simulating the hysteretic behavior of composite‐steel beams as part of fully restrained beam‐to‐column connections in composite‐steel moment‐resisting frames (MRFs). Comparisons with experimental data suggest that the proposed model captures the asymmetric hysteretic response of composite‐steel beams including the cyclic deterioration in strength and stiffness. Moreover, the proposed model captures the primary slab‐column force transfer mechanisms and predicts the slip demands in beam‐slab connections under inelastic cyclic loading. The modeling approach is employed in a system‐level study to benchmark the seismic collapse risk of composite‐steel MRF buildings across Europe. Moreover, the beam‐slab slip demands are quantified through the development of beam‐slab slip hazard curves. The simulation studies suggest that the examined composite‐steel MRFs exhibit a system overstrength of about 4. This is attributed to the drift requirements in the current European seismic provisions.1 The annualized probability of collapse of the prototype buildings is well below 1% over a 50‐year building life expectancy regardless of the design site and the degree of composite action. Beam‐slab connections with a partial degree of composite action experience minimal damage for frequently occurring seismic events (i.e., 50% probability of exceedance over 50 years); and light cracking in the slab for a design basis earthquake. The above are important from a seismic repairability standpoint. Accordingly, it is recommended that the 25% reduction in the shear resistance of stud connectors is not imperative for seismic designs that feature steel beams with depths less than 500 mm. [ABSTRACT FROM AUTHOR]

Precast reinforced concrete panels are commonly used as wall claddings in precast buildings. The cladding panels are generally evaluated as non-structural members and are joined to structural systems via mechanical, welding, and bolted dry connections. Several failures were observed in the last seismic events in Southern Europe, which demonstrate the deficiencies of the cladding connections in terms of strength and ductility. A comprehensive research activity named SAFECLADDING was conducted in Europe to provide knowledge for proper seismic design of precast structures with cladding panels. In this context, energy dissipative steel cushions were developed and evaluated through the extensive experimental and numerical studies. Steel cushions can provide robust interaction of the structural system with the cladding panels. This paper numerically evaluates the effects of cladding panels with steel cushions on the global seismic behaviour of the buildings. An existing representative industrial building is selected to perform intensive nonlinear dynamic analyses. Analyses performed on the bare and hybrid systems showed that the hybrid system has high performance in terms of story drifts, internal forces, and deformations with respect to the bare system. The overall drifts in longitudinal and transversal directions of the building are reduced by about 78 and 54%, respectively. Average residual drifts of cladding panels and steel cushions indicated that the applied steel cushion placement scheme has a promising re-centring capability during seismic action. [ABSTRACT FROM AUTHOR]

As part of the development of a European Seismic Risk Model 2020 (ESRM20), the spatial and temporal evolution of seismic design across Europe has been studied in order to better classify reinforced concrete buildings (which represent more than 30% of the approximately 145 million residential, commercial and industrial buildings in Europe) and map them to vulnerability models based on simulated seismic design. This paper summarises the model that has been developed to assign the years when different seismic design levels (low code, moderate code and high code) were introduced in a number of European countries and the associated lateral forces that were specified spatially within each country for the low and moderate codes for typical reinforced concrete mid-rise buildings. This process has led to an improved understanding of how design regulations evolved across Europe and how this has impacted the vulnerability of the European residential building stock. The model estimates that ~ 60% of the reinforced concrete buildings in Europe have been seismically designed, and of those buildings ~ 60% have been designed to low code, ~ 25% to moderate code and 15% to high code. This seismic design model aims at being a dynamic source of information that will be continuously updated with additional feedback from local experts and datasets. To this end, all of the data has been made openly available as shapefiles on a GitLab repository. [ABSTRACT FROM AUTHOR]

The current paper presents a preliminary algorithm most commonly used for designing the base isolation devices. The algorithm addresses exclusively the base isolation systems which use Laminated Rubber Bearings (LRBs), one of the most used devices in the world. In the first part of the paper the theoretical aspects will be presented by focusing on two different designing approaches (stress approach and strain approach). The seismic conditions will be defined according to three different seismic codes: the European Code (EUROCODE- 1998), the Italian Code and the Romanian Code. In the second part of the paper, several parametrical studies are performed using the designing procedure presented in the first part. The aim of these studies is to obtain a clear understanding of the design procedures and also to determine the influence of seismic characteristics on studied parameters. Finally, the last part of the paper presents a comparison between different solutions obtained for the base isolation system when we consider the same building (Demonstration building on HDNR isolators situated near Java, Indonesia) and different seismic parameters. The chosen seismic conditions correspond to the seismic parameters defined by the above mentioned codes. [ABSTRACT FROM AUTHOR]

The seismic design of structures according to current codes is generally carried out using a uniform-hazard spectrum for a fixed return period, and by employing a deterministic approach that disregards many uncertainties, such as the contribution of earthquake ground motions with return periods other than that assumed for the design. This results in uncontrolled values of the failure probability, which vary with the structure and the location. Risk targeting has recently emerged as a tool for overcoming these limitations, allowing achievement of consistent performance levels for structures with different properties through the definition of uniform-risk design maps. Different countries are implementing the concepts of risk targeting in different ways, and new methods have recently emerged. In the first part of this article, the most well-known approaches for risk targeting are reviewed, with particular focus on the one implemented in recent American design codes, the one based on the use of risk-targeted behaviour factors (RTBF), and an approach based on direct estimation of hazard curves for inelastic response of single-degree-of-freedom systems. The effect of the linearization of the hazard curve is investigated first. A validation of the RTBF approach is then provided, based on comparison with the results of uniform-risk design spectral accelerations for single-degree-of-freedom systems with elastic-perfectly plastic behaviour for two different sites. The effectiveness of the current risk-targeting framework applied in the United States is also investigated. In the last part of the paper, uniform-risk design maps for Europe are developed using the RTBF approach, showing how the seismic design levels may change when moving from a uniform-hazard to a uniform-risk concept. [ABSTRACT FROM AUTHOR]

Numerous countries across the globe have witnessed the recent decades' trend of multi-storey timber buildings on the rise, owing to advances in engineering sciences and timber construction technologies. Despite the growth and numerous advantages of timber construction, the global scale of multi-storey timber construction is still relatively low compared to reinforced concrete and steel construction. One of the reasons for a lower share of high-rise timber buildings lies in the complexity of their design, where the architectural design, the selection of a suitable structural system, and the energy efficiency concept strongly depend on the specific features of the location, particularly climate conditions, wind exposure, and seismic hazard. The aforementioned shows the need for a comprehensive study on existing multi-storey timber buildings, which correspond to the boundary conditions in a certain environment, to determine the suitability of such a construction in view of its adjustment to local contexts. Apart from exposing the problems and advantages of such construction, the current paper provides a brief overview of high-rise timber buildings in Europe. Moreover, it addresses the complexity of the design approach to multi-storey timber buildings in general. The second part of the paper highlights the importance of synthesising the architectural, energy, and structural solutions through a detailed analysis of three selected case studies. The findings of the paper provide an expanded view of knowledge of the design of tall timber buildings, which can significantly contribute to a greater and better exploitation of the potential of timber construction in Europe and elsewhere. [ABSTRACT FROM AUTHOR]

The seismic performance and safety of major European industrial facilities have a global interest for the whole of Europe and its citizens. However, the seismic design of these facilities is based on national, sometimes outdated seismic hazard analyses. The results of the commonly developed, fully harmonized newly released European Seismic Hazard Model ESHM20 provide a pertinent reference for seismic hazard at European scale and have been officially adopted as an "acceptable representation of the seismic hazard in Europe" in the ongoing revision of Eurocode 8. This study presents a large-scale investigation of the impact of the potential adoption of ESHM20 on the design of new industrial facilities as well as on the potential seismic risk of existing facilities at European level with respect to the current seismic codes. The horizontal elastic response spectra using ESHM20 in combination with the revised Eurocode 8 for selected industrial sites are compared with the respective response spectra of the national regulations for return periods of 475, 2500 and 5000 years. In addition, a single containment LNG tank is analysed for an industrial site in Germany using the design approach for liquid filled tanks according to the revised Eurocode 8. Furthermore, a deterministic and probabilistic seismic risk assessment of a vessel installed in a five-storey frame is performed for industrial sites in Greece and Germany. The examples show that a consistent procedure all over Europe would be desirable and a benefit for engineers in terms of comparability and achievement of the same safety targets. Based on the conducted illustrative studies, the consequences of a potential adoption of the revised Eurocode 8 and ESHM20 hazard maps are discussed and summarized with respect to the standard harmonisation process in Europe. [ABSTRACT FROM AUTHOR]

Most of existing steel multi-storey frames in Europe have been designed before the introduction of modern seismic design provisions, hence they often exhibit low performance under earthquake loads due to their low lateral resistance and energy dissipation capacity. In addition, such structures often include rigid and brittle masonry infill walls that highly influence their lateral response and distribution of damage pattern. However, current procedures for the assessment of existing steel buildings in Europe, included in the Eurocode 8 – Part 3 (EC8–3), do not provide adequate guidance for the assessment of 'weak' steel frame with masonry infill walls. Moreover, most of available modelling approaches of masonry infills formerly developed for reinforced concrete (RC) structures do not properly represent the behaviour of infill walls in steel frames. An improved numerical has to be provided to satisfactorily mimic infill walls' behaviour in steel moment frames. To this end, an experimental and theoretical study was carried out within the framework of HITFRAMES (i.e., HybrId Testing of an Existing Steel Frame with Infills under Multiple EarthquakeS) SERA project. This paper firstly presents the limitations of current EC8–3 by conducting a code-based assessment on a case study steel moment frame using pushover analysis. Three different single strut models, widely used for simulating the presence of masonry infills in RC structures, are considered for the numerical analyses. The paper also presents the results of pseudo-dynamic (PsD) tests performed on a large-scale 3D steel frame with masonry infills. The capability of the different masonry infill models is successively evaluated by comparisons between numerical and experimental results. On the basis of the obtained results, recommendations on how to potentially improve the single strut model for masonry infills surrounded by steel frames are also provided. [Display omitted] [ABSTRACT FROM AUTHOR]

Beam-to-column joints are commonly considered critic regions for RC frames subjected to earthquake actions. When designed for gravity loads only, beam-to-column corner joints strongly affect the global structural behaviour of a frame, and they can be cause of its collapse, as shown by recent earthquakes in Europe. In the paper, a component-based f.e. model for external beam-to-column joints is presented to simulate the seismic behaviour of r.c. existing structures designed without any capacity design criteria (smooth bars with hooked-end anchorages and with no transverse reinforcements in the joint). The joint deformation is modelled by means of two separate contributions, the shear deformation of the panel zone, and the rotation at the interface sections between the joint and the structural members, due to the reinforcing bars’ slip within the joint core. The work focuses on the evaluation of the joint strength and stiffness, and it points out the importance of modelling the bar bond slip within the panel zone to describe the actual frame response. The component-based f.e. model is validated by experimental results of tests on beam-to-column corner joints realized according to the construction practice of the 1960s–1970s in Italy, thus confirming the effectiveness of the presented model for the assessment of existing structures. [ABSTRACT FROM AUTHOR]

With accumulated experiences of bridge damage learned from past earthquake events, the highway bridge seismic design approach is evolving from time to time. It is important for both China and Europe to learn from each other to improve seismic design approaches. A thorough comparison relating to the seismic hazard level, response spectra, and ductility considerations between Eurocode 8 and the Chinese specification is made in this study. Both of these two specifications are based on performance-based design philosophy. However, the Chinese specification is based more on deformation capacity than on strength. The design approach specified in the Chinese specification is more consistent with experiences obtained from past earthquake events than the method adopted in Eurocode 8. Case study shows that bridge designed in accordance with Eurocode 8 could satisfy the force requirement under earthquake action E1 as specified in the Chinese specification but could not satisfy the displacement requirements under earthquake action E2. It is expected that the method adopted in the Chinese specification could provide conservative seismic design in both aspects of seismic forces and displacements. [ABSTRACT FROM AUTHOR]

This paper presents a comparative evaluation among some international, European and American, seismic design standards. The study considers the criteria for the analysis of conventional (residential and commercial) buildings. The study is focused on some critical topics: definition of the recurrence periods for establishing the seismic input; definition of the seismic zonation and shape of the design response spectra; consideration of local soil conditions; definition of the seismic force-resisting systems and respective response modification coefficients; definition of the allowable procedures for the seismic analysis. A model for a standard reinforced concrete building ("Model Building") has been developed to permit the comparison among codes. This building has been modelled with two different computer programs, SAP2000 and SOFiSTiK and subjected to seismic input according to the several seismic codes. The obtained results compared are leading to some important conclusions. [ABSTRACT FROM AUTHOR]

Abstract: The recent introduction of a common basis for structural design in Europe has led to a comprehensive set of standards covering the most used building materials. The basic principles of proper design are stated in EN 1990 and the actions are specified in EN 1991. For timber structures the governing regulations are given in EN 1995 (Eurocode 5), with the exception of seismic design which is covered by EN 1998. EN 1995 complies with the principles of EN 1990, but it is only concerned with requirements for mechanical resistance, serviceability, durability and fire resistance. When it comes to the principle stating that potential damage shall not be disproportionate to the original cause, and the principle statement on limitations of potential damage, EN 1995 offers very little help on how to fulfil these principles. In ultimate limit states there are no recommendations or guidance on deformations, rotations or other measures for evaluation of, to what extent, a timber structure fulfils the basic principles of EN 1990. Ductility and robustness of timber structures are high on the agenda of the COST action E55. Contributions are needed in order to develop methods for verification of compliance with the basic principles of EN 1990. The most common opinion in recent literature is that this can be achieved by utilization of plastic deformation of metallic fasteners. However, although numerous experimental results on the behavior of timber structures, timber connections and metallic fasteners are reported, no unified methods exist for evaluation of these results in this context. In EN 1995, the required properties are not stated, nor is there any method available for verification. In the paper some procedures are proposed and discussed. Furthermore, some ductility measures are used in evaluations of examples from tested structural timber connections. The results are discussed in view of the definition of ductility and the basic requirements of design put forward in EN 1990. [Copyright &y& Elsevier]

The growing seismic networks and the increasing number of permanent seismic stations can help in improving the physical basis of seismic hazard assessment. For this purpose, the definition of reference site conditions is of great significance. If a reliable estimate of the reference ground motion is known, its modification at any given site can be modelled with respect to that reference site. Since the choice of a well-characterized reference site is not straightforward, mainly due to the high variability in the shallow layers, such choices prove to be affected by large uncertainties. While proxy parameters like the average S -wave velocity over the uppermost 30 m (v S30) might help in characterizing reference site conditions, such parameters are neither available at all sites nor do they allow concluding that the site is not affected by amplification and attenuation effects. In this study, we identify prospective reference sites across Europe in a harmonized and fully data-driven way. All analysis is based on freely available geological and geophysical data and no on-site measurements or site-specific proxies are required. The study accounts for both the influence of amplification and attenuation in a large frequency range. To address the key conceptual issues, we verify our classification based on machine learning techniques in which the influence of the individual site characterization parameters is investigated. Our study indicates that around 250 sites in Europe over more than 2000 investigated are not affected by local site effects and can de facto be considered as reference sites based on the criteria applied. [ABSTRACT FROM AUTHOR]

The current design approach recommended by seismic codes is often based on the use of uniform-hazard response spectra, reduced to account for inelastic structural behaviour. This approach has some strong limitations that have been highlighted in many studies, including not allowing a direct control of the seismic risk and losses. This study aims at quantifying the levels of safety and the costs associated with this design approach, and to investigate alternative design approaches that have been developed in the last decades. In particular, a risk-targeting approach and a minimum-cost approach are considered. The first one, allowed by US codes, aims at designing structures with the same risk of collapse throughout regions of different seismicity. The second one aims to minimize the sum of the initial construction cost and the cost of expected losses due to future earthquakes. The comparison of the three approaches is performed by considering, as an example structure, a four-storey reinforced concrete frame building located in different areas in Europe, and by looking at the implications in terms of achieved safety levels, initial costs, and future losses. The study's results provide useful information on how the design criteria and the different hazard levels throughout Europe affect the cost and safety levels of seismic design. [ABSTRACT FROM AUTHOR]

Ground motion models (GMMs) are a key component in seismic hazard assessment and in seismic risk analysis. The consideration of both aleatory and epistemic sources of variability may have significant influence on the results and are vital because of their influence on the over- or under-estimation of the final assessment of losses. Recent research has shown that the commonly used framework of weighted logic trees for the choice of GMMs is not necessarily the best suited to account for epistemic uncertainty. Recently, a simple and alternative procedure has been proposed in which a GMM suite is defined with only three representative models (lower, central and upper) derived from available median models. This alternative model is equivalent to the use of multiple models, provided the same range of epistemic uncertainty is sampled. The representative suite approach was applied to the European context for developing a Pan-European GMM for EC8 ground type B and normal or strike slip faulting style for its implementation in risk analysis of critical infrastructures Europe wide, within the framework of the European funded project INFRARISK. The proposed new Pan-European representative GMM is based on the most recent GMMs developed using the common RESORCE strong-motion database of European and Near and Middle East acceleration records. It is shown to perform well when tested against new ground-motion observations from the ESM-Engineering Strong-Motion database and even slightly better than other available GMMs. The procedure is efficient and transparent limiting the sample space to three GMMs and reducing both complexity of the modelling and computational efforts. [ABSTRACT FROM AUTHOR]

Experience of designing buildings with structural masonry walls and masonry non-structural elements using Codes CR 6-2006 [15a] and P 100-1/2006 [16a], that were developed based on design principles and rules of Eurocodes adopted in Romania SR EN 1996-1-1[13] and SR EN 1998-1[14], revealed the need of some additions and corrections of texts. These interventions made by developing Codes CR 6 -2013[15] and P 100-1/2013[16], which we can characterize synthetically as follows: - Are aligned with the Structural Eurocodes principles but correcting some identified deficiencies. - Resume some previous provisions of national regulations that lack in Eurocodes - Introduce the results of recent theoretical and experimental research - Provide practical application rules, simple and explicit, accompanied by "Commentary" and "Design examples" The communication exposes and justifies synthetically the following new approaches introduced in the 2013 editions of the two regulations: I. Modification of the methodology for the partial safety factors (γM) and for establishing the minimum necessary strength values of masonry. II. Additions and explanations of the design rules for unreinforced and confined masonry subjected to combined axial compression and flexure and to shear loading. [ABSTRACT FROM AUTHOR]

We present the results of ground-based Ultra Low Frequency (ULF) magnetic field measurements observed from June to August 2004 during the Bovec earthquake on 12 July 2004. Further we give information about the seismic activity in the local observatory region for an extended time span 2004 and 2005. ULF magnetic field data are provided by the South European Geomagnetic Array (SEGMA) where the experience and heritage from the CHInese MAGnetometer (CHIMAG) fluxgate magnetometer comes to application. The intensities of the horizontal H and vertical Z magnetic field and the polarization ratio R of the vertical and horizontal magnetic field intensity are analyzed taking into consideration three SEGMA observatories located at different close distances and directions from the earthquake epicenter. We observed a significant increase of high polarization ratios during strong seismic activity at the observatory nearest to the Bovec earthquake epicenter. Apart from indirect ionospheric effects electromagnetic noise could be emitted in the lithosphere due to tectonic effects in the earthquake focus region causing anomalies of the vertical magnetic field intensity. Assuming that the measured vertical magnetic field intensities are of lithospheric origin, we roughly estimate the amplitude of electromagnetic noise in the Earths crust considering an average electrical conductivity of <σ>=10-3 S/m and a certain distance of the observatory to the earthquake epicenter. [ABSTRACT FROM AUTHOR]

Recent developments in displacement-based design methodologies have increased the need for reliable displacement design spectra, especially in long periods. The design spectra proposed in Eurocode 8 are assessed, using recent attenuation relationships that predict response spectral ordinates based on European data, as well as five selected European strong motion accelerograms. To identify possible trends in long-period spectral displacements, several high-quality digital recordings from the 1995 Hyogoken-Nanbu (Kobe) earthquake were collected and studied. Based on the differences recognised, possible modifications for the design spectrum to take into account in future revision of Eurocode 8 are proposed. [ABSTRACT FROM AUTHOR]