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Integral abutment bridges (IABs) generate strong soil–structure interaction (SSI) effects due to their high structural stiffness and transmission of inertial and thermal loads generated at the deck directly to the abutments. Despite an increasing number of experimental and numerical studies available in the literature, there is a lack of consolidated methodologies to model dynamic SSI phenomena for IABs, particularly in seismic regions where uncertainties associated with the induced ground motions render the problem harder to tackle. This study proposes an advanced strategy to model the seismic response of IABs, accounting for dynamic interaction between the structure, the abutment and the foundation, including piles and earth retaining walls. To this end, detailed finite‐element studies were carried out employing OpenSees to simulate a recent experimental campaign on a scaled IAB model in a soil container (SERENA) carried out at EQUALS Lab, University of Bristol, in the framework of SERA/H2020 project. An extensive dataset in terms of recorded accelerations, displacements, strains and settlements are available from these tests, including earth pressures which are back‐calculated from bending strain measurements. The objectives of this paper are threefold: firstly, the model parameters are explored and assessed critically by comparing the results from the numerical simulations against the experimental data; secondly, once the model is deemed sufficiently representative of the experiments, earth pressures are obtained numerically, as these are not directly measured in the tests; thirdly, the estimated static and dynamic earth pressures on the abutment wall are compared with the predictions of two simplified analytical procedures currently under consideration for inclusion in the new Eurocode 8. The results indicate that records and predictions match well for frequencies of up to 40 Hz at model scale (about 8 Hz in prototype scale) and confirm that the proposed modelling strategy can be used in practical applications. The quasi‐elastic model proposed in this study is shown to provide dependable predictions for cases involving moderate strains in real‐life applications. [ABSTRACT FROM AUTHOR]

The shear resistance computed using Annex J of Part 1–1 of Generation 2 of Eurocode 2—on strengthening of RC members for static loads with externally-bonded Fibre-reinforced-polymers (FRPs)—exceeds by about 25% on average the cyclic shear resistance of 64 FRP-jacketed shear-critical RC specimens in the international literature. The semi-empirical cyclic shear resistance approach for FRP-wrapped RC members in Annex A of Part 3 of Generation 1 of Eurocode 8 is in good average agreement with the results of these tests, but conflicts with the rational, mechanics-based approach for shear resistance against static actions in Generation 2 of Eurocode 2, which has already been adopted in Generation 2 of Eurocode 8 for members without FRP jackets, adapted to the specific needs of seismic design. This latter approach is modified and extended to cover RC members with closed FRP jackets in a more technically sound way than in Annex J of Generation 2 of Eurocode 2. The new approach fits the available cyclic test results without bias or lack-of-fit with respect to the key variables controlling cyclic shear resistance, gives slightly better accuracy than the semi-empirical one in Generation 1 of Eurocode 8 and does much better in correctly identifying as not failing in shear FRP-wrapped RC members which have failed in flexure or not failed at all during cyclic testing. [ABSTRACT FROM AUTHOR]

Large databases of cyclic tests on flexure‐ or shear‐critical concrete members and shear‐critical connections of columns to beams or slabs are used to estimate the uncertainty inherent in experimental data in literature—as read by users. To this end, the predictions of two different, presumably independent, design‐oriented models for the properties of interest are used to establish the "central tendency" of data, against which individual tests or small groups thereof are assessed. Properties considered are: (a) the cyclic ultimate chord‐rotation of flexure‐controlled members with continuous or lap‐spliced deformed bars, (b) the cyclic shear strength of shear‐critical members, (c) the chord‐rotation at yielding of rectangular columns with plain bars, and (d) the cyclic shear strength of shear‐controlled beam‐column and slab‐column joints. Results suggest that the data from each test campaign have a certain degree of bias, specific to it. Test campaigns with ratio of estimated average deviation from the "central tendency" to the standard deviation of campaign deviations (called "data uncertainty") which is far into the tail of the Normal distribution may be excluded as questionable. This systematic bias, along with other types of "data uncertainty" addressed in this work, seem to contribute to the apparent scatter of model predictions with respect to cyclic test results the equivalent of a coefficient of variation of model‐to‐test‐ratio of at least 10% and possibly as high as 25%–30%. Model uncertainty seems to contribute to this scatter the equivalent of a coefficient of variation of at least 15% in shear‐controlled connections, or as much as 25% in the case of flexural deformation capacity of members with deformed bars; the cyclic shear resistance of members and—with the reservation of the small number of tests—the chord‐rotation at yielding of members with plain bars, are in‐between. [ABSTRACT FROM AUTHOR]

Abstract This paper demonstrates the enhanced resilience performance of steel structures with viscoelastic friction dampers (VEFDs) based on numerical simulations of building responses. Velocity-dependent dampers, which are widely used to increase seismic resilience, may increase the axial force of the column under strong earthquake conditions because the generated force depends on the interstory velocity. This often leads to plastic hinges being placed on the columns of the structure, which can lead to structural collapse via weak-layer failure. In addition, while viscoelastic dampers are effective in reducing story drift, peak acceleration, and peak velocity, the proposed hybrid VEFD offers the additional benefit of reducing base shear via the friction damper. Simulation results for 10- and 20-story buildings with the novel VEFDs show that the proposed dampers can control drift and plastic deformation in structural members. Nonlinear dynamic analysis of 20 far-fault seismic ground motion records conducted using OpenSees also reveals lower peak absolute floor acceleration and velocity. Overall, the results suggest that the proposed VEFD has excellent potential for use in the performance-based seismic design of structures because it can reduce both structural and nonstructural damage. The results verify the damper's effectiveness in controlling story drift without a significant increase in the base shear. Collapse probability assessment also demonstrates the collapse resistance of moment-resisting frames when used in conjunction with VEFDs.

Eurocode 8 is undergoing a revision process encompassing novel ductility classes, damage limitation limits, local ductility conditions corresponding to detailing prescriptions and structural irregularity criteria. In this paper, we specifically assessed the influence of an irregularity in elevation, imposed by different elevations, on the first and third storeys of buildings, and variations in the cross-sections of columns during the seismic response of reinforced concrete (RC) structures. To assess this impact, an extensive examination was conducted on thirteen five-storey moment-resisting frame (MRF) buildings. The design of those structures was carried out on the Robot Structural Analysis Professional framework following the current generation of Eurocodes 2 and 8, and the seismic response analysis was carried out using the SeismoStruct v2024 software. The results were compared to evaluate the influence of imposed irregularities in elevation due to the increasing height, column cross-section, mass, and resistance variation. The study's outcomes revealed that, for DCM structures, the imposed irregularities in elevation have different impacts on the seismic response. Increasing the heights of ground or middle floor have substantial deleterious effects on the building's seismic response. The planned geometry and variations in the cross-sections of columns substantially impact inter-storey drift and base shear. The effects of mass and resistance irregularities were neglected in this study. As such, more studies on those matters are necessary to allow our results to be further generalised. [ABSTRACT FROM AUTHOR]

This paper demonstrates the enhanced resilience performance of steel structures with viscoelastic friction dampers (VEFDs) based on numerical simulations of building responses. Velocity-dependent dampers, which are widely used to increase seismic resilience, may increase the axial force of the column under strong earthquake conditions because the generated force depends on the interstory velocity. This often leads to plastic hinges being placed on the columns of the structure, which can lead to structural collapse via weak-layer failure. In addition, while viscoelastic dampers are effective in reducing story drift, peak acceleration, and peak velocity, the proposed hybrid VEFD offers the additional benefit of reducing base shear via the friction damper. Simulation results for 10- and 20-story buildings with the novel VEFDs show that the proposed dampers can control drift and plastic deformation in structural members. Nonlinear dynamic analysis of 20 far-fault seismic ground motion records conducted using OpenSees also reveals lower peak absolute floor acceleration and velocity. Overall, the results suggest that the proposed VEFD has excellent potential for use in the performance-based seismic design of structures because it can reduce both structural and nonstructural damage. The results verify the damper's effectiveness in controlling story drift without a significant increase in the base shear. Collapse probability assessment also demonstrates the collapse resistance of moment-resisting frames when used in conjunction with VEFDs. [ABSTRACT FROM AUTHOR]

Three concrete buildings with six storeys above ground and two basements have been designed in detail according to the first generation of Eurocodes 2 (including structural fire design) and 8, as well as the official drafts of their second generation counterparts as of the end of 2023. In one horizontal direction the buildings have a wall-, frame-equivalent-dual- or frame-lateral-load-resisting system; in the other, the first two buildings have a wall-system and the third a wall-equivalent-dual. The design seismic action is in all cases according to the current generation Eurocode 8, scaled to a peak ground acceleration on rock of 0.2 or 0.3 g. Seismic design is for ductility class (DC) Medium (M) of the current generation or DC 3 of the new one, which have the same behaviour factors, q, in all structural systems considered; so, in each building seismic action effects from the analysis are the same for the two Eurocode generations. All designs are assessed through nonlinear response history analysis (NLRHA), carried out according to the pertinent Eurocode 8 rules. Designs according to the second generation meet the performance goals of Eurocode 8 much better and transparently than with the first generation, but use markedly larger steel quantities and indeed often unnecessarily so, especially for confining reinforcement—which sometimes comes out in quantities that cannot be placed. Proposals are made for a more rational linkage of local ductility demands with the q-factor and implemented in alternative second generation designs. Minor changes to the new generation's design/detailing rules for ductile walls are also proposed and implemented in these alternative designs; they prove only partially effective in resolving certain deadlocks originating from poorly justified detailing rules that produce unnecessary and counterproductive wall flexural overstrengths. The new generation Eurocode 8 lacks design rules for the free height of ductile walls within rigid basements, which is a weak link, very likely to fail under the high shear force which balances the wall's moment resistance at the top of the rigid basement. NLRHA confirms that the alternative provisions proposed for second generation Eurocode 8 give more cost-effective designs than the first generation, with better overall performance at about the same or even lower cost. [ABSTRACT FROM AUTHOR]

The Greek National Annex for current Eurocode 8 has adopted the seismic hazard zonation map published in 2003 as part of the modifications to the Greek Seismic Code EAK 2000 (EAK 2003). This map, which followed the catastrophic earthquakes that hit the country between 1978 and 2001, includes three seismic hazard zones with peak ground acceleration (PGA) ranging between 0.16 and 0.36 g. In this paper, following the significant progress that has been made worldwide in the last two decades towards the improvement of the definition of seismic actions and the seismic hazard maps using fully probabilistic models, we make a complete proposal for the Greek National Annex of the ongoing revision of Eurocode 8, which includes a new seismic hazard zonation map for Greece, as well as a novel site categorization scheme and related site amplification factors. To this end, we use the results of the European Seismic Hazard Model, ESHM20, as reported by Danciu et al. (The 2020 update of the European Seismic Hazard Model: Model Overview, 2021) which will be adopted as informative reference for the seismic hazard at European level in the forthcoming revision of Eurocode 8 (CEN/EC8). The herein proposed ground shaking zonation for rock conditions includes five zones with PGA values ranging between 0.13 and 0.37 g. For each zone, two newly proposed ground motion parameters, i.e., Sα,475 and Sβ,475, are provided, which are the two parameters used for anchoring the elastic response spectrum as defined in CEN/EC8, along with all the other necessary parameters for the definition of the elastic response spectrum, including site amplification. The proposal for the new seismic zonation is supported by a preliminary investigation of the impact of its adoption on the seismic design of new structures and on the seismic risk of the current building stock in Greece, to help gain a better insight on how important the differences imposed by the new zonation might be for the end-users and the administration. [ABSTRACT FROM AUTHOR]

Background: The dynamic response of large-scale structures requires a good representation of seismic excitations. These structures are subjected to spatial variability of seismic ground motion. This seismic variability results from the propagation of seismic waves between the focus and the site. The RPOA (the Algerian Bridge Seismic Regulation Code) and Eurocode 8 (EC8) introduce simplified approaches for spatial variable ground motion. Purpose: The main objective of this paper is the evaluation of the accuracy of the methods proposed by the RPOA through comparison with the EC8 provisions. Method: The longest railway viaduct in Algeria is used as a case study in this work. The dynamic analysis based on the modal spectral dynamic method is adopted according to RPOA and Eurocode 8 seismic codes. Results and conclusion: The results show that the method proposed by RPOA to consider the spatial variability of ground motion clearly overestimates the seismic demand. Therefore, the RPOA method gives internal forces much higher than those calculated from Eurocode 8. [ABSTRACT FROM AUTHOR]

The method for the direct determination of floor acceleration spectra, previously developed by the authors, is extended in order to take into account the nonlinear component behaviour. In the case of a linear elastic response of both the primary structure and the component, the component may be exposed to very high accelerations during seismic actions. The component accelerations can be greatly reduced if the response of the structure and/or the component is nonlinear. Considerable research work on the effect of the nonlinearity of structures has already been performed, whereas relatively sparse information is available on the quantitative influence of the component nonlinearity on its response. In the paper, first, the results of a parametric study of floor acceleration spectra for nonlinear components are shown and discussed. Then, the proposed extension of the existing authors' method is described and validated by test examples. In addition, an approximate approach for the estimation of floor acceleration spectra for nonlinear components by using an increased component damping value is presented. In the proposed method, floor acceleration spectra are, to a great extent, based on the theory of the dynamics of structures, and partly combined with empirical values and well established approaches for considering nonlinear effects. Floor acceleration (response) spectra explicitly take into account ground motion spectra and dynamic characteristics of buildings and components. The advantage of such an approach is its general applicability, which allows diverse design options. [ABSTRACT FROM AUTHOR]

Masonry has been widely used for the construction of residential buildings in Serbia and the majority of European countries. Confined masonry (CM) is a contemporary masonry technology that consists of load-bearing masonry walls enclosed in lightly reinforced horizontal and vertical reinforced concrete (RC) confining elements. CM has been widely used for the construction of low-rise and mid-rise residential buildings in Serbia and the region (Yugoslavia) since the 1960s. The design case study of a typical multi-family residential building located in Niš, Serbia (the third-largest urban center in the country), is discussed in this paper. This building was initially designed as a five-story CM structure in accordance with the 1981 Yugoslav seismic design code PTN-S, which was enforced in Serbia until 2019, when the Eurocode was adopted for official seismic design codes. Due to architectural constraints, the original design solution involving the CM system was not compliant with the code; hence, an alternative design using an RC-frame system with masonry infills was adopted. A comparison of two different design solutions provides insight into the different requirements of seismic design codes that have been used in the region. It is important to observe that seismic forces for RC structures determined in accordance with the PTN-S code are considerably lower compared to the ones determined according to EC 8-1, with the ratio ranging from 0.37 to 0.69. The seismic shear force according to Eurocode 8 is 1.46 times higher than the force that was used for seismic design according to the PTN-S code in the case of RC-frame structures. The results of an analysis of CM structures show that the seismic shear force in accordance with Eurocode 8 is almost 2.6 times higher than the force that was used for seismic design in accordance with the PTN-S code. The findings of this study are believed to be useful for understanding the difference in seismic design solutions for previous seismic design codes (which were used in the region for more than 40 years) and the present codes (Eurocodes). [ABSTRACT FROM AUTHOR]

A proposal to control the structural pounding hazard imposed on multistory reinforced concrete (RC) structures is presented. The main goal is to guarantee the seismic performance of a structure with an acceptable (predefined) risk-targeted parameter without the need to eliminate structural pounding collisions. The key target parameters of this study are the annual probability of exceeding an engineering demand parameter (EDP) capacity level and the separation distance dg between adjacent structures. In this direction, a method that ensures the performance level of critical EDPs due to structural pounding conditions is proposed. The new method involves two decision frameworks that define (a) the optimal separation gap distance d g , m i n P t at a targeted value of pounding risk (probability per year) Pt (Decision A) and (b) the minimum acceptable structural pounding risk P m i n d g , t at a targeted value of separation gap distance dg,t (Decision B). The demand parameters that are incorporated in the proposed method are the peak relative displacement δmax at the top level of colliding without considering pounding conditions and any other critical EDP due to the structural pounding effect. The overall method is based on two distinct acceptable performance objectives, the POs-δmax and the POs-EDP, defined as a function of P vs. dg. For this purpose, a seismic hazard curve compatible with Eurocode's 8 hazard zone is adopted, and the corresponding demand hazard curves of δmax and EDP are developed. The proposed method is implemented to study the floor-to-floor structural pounding hazard of an eight-story RC frame taking into account different risk-targeted scenarios. The results show that the seismic risk (probability per year) of exceeding the EDP's capacity level is significantly increased due to structural pounding in comparison to the case of no pounding. Calibration of the structural pounding risk can be obtained by adjusting the separation gap distance dg between the adjacent structures based on the acceptable POs. The POs-δmax is not always an accurate criterion for verifying the capacity level of the critical EDP. Finally, with the proposed method, a variety of POs-EDPs can be used to control the structural pounding risk in terms of d g , m i n P t and/or P m i n d g , t . [ABSTRACT FROM AUTHOR]

Eurocode 8 is undergoing a revision process encompassing novel ductility classes, damage limitation limits, local ductility conditions corresponding to detailing prescriptions and structural irregularity criteria. In this paper, we specifically assessed the influence of an irregularity in elevation, imposed by different elevations, on the first and third storeys of buildings, and variations in the cross-sections of columns during the seismic response of reinforced concrete (RC) structures. To assess this impact, an extensive examination was conducted on thirteen five-storey moment-resisting frame (MRF) buildings. The design of those structures was carried out on the Robot Structural Analysis Professional framework following the current generation of Eurocodes 2 and 8, and the seismic response analysis was carried out using the SeismoStruct v2024 software. The results were compared to evaluate the influence of imposed irregularities in elevation due to the increasing height, column cross-section, mass, and resistance variation. The study’s outcomes revealed that, for DCM structures, the imposed irregularities in elevation have different impacts on the seismic response. Increasing the heights of ground or middle floor have substantial deleterious effects on the building’s seismic response. The planned geometry and variations in the cross-sections of columns substantially impact inter-storey drift and base shear. The effects of mass and resistance irregularities were neglected in this study. As such, more studies on those matters are necessary to allow our results to be further generalised.

Eurocode 8 is currently under revision, and their amended versions will be available in the next few years. One of the major novelties of the second generation of Eurocode 8 is a specific chapter for the seismic design of aluminium buildings (i.e., Chapter 15) that is missing in the current EN1998-1:2005. Thus, the second generation of Eurocode 8 is the first European set of rules for seismic-resisting aluminium structures. These new rules are mainly based on the current Japanese recommendations, but adapted to Eurocode philosophy. The main novelties of the second generation of Eurocode 8 and the requirements for seismic-resistant aluminium structures are summarised in the present article. [ABSTRACT FROM AUTHOR]

The aim of the work is to make a comparison between the European and Japanese approaches to design Seismic‐Resistant Steel Frames (MRFs) in high seismicity areas. Therefore, the design rules for both the seismic codes are analyzed and compared. These design rules are applied to design a benchmark structure in DC3 ductility class (according to the new prEN1998) and following the Route 3 procedure (according to the Building Standard Law in Japan, BSL). The examined structural typology is a Spatial Moment Resisting Frames with regularity in plan and elevation configuration. The Japanese approach is divided in two stages. The first one regards the Allowable Stress Design (Elastic analysis) in which all the parts of the structure must be kept elastic; service and damage limitation requirements are in demand. The second stage regards the Ultimate Strength Design (Plastic Analysis) in which no‐collapse requirement and the protection of the human life are in demand. The seismic performance of the designed structures is evaluated by means of pushover analyses. [ABSTRACT FROM AUTHOR]

This paper deals with the modelling and assessment of the inelastic cyclic behaviour of composite members consisting of steel beams and reinforced concrete slabs, designed to European standards. The work involves the development of detailed continuum models that can simulate the asymmetric behaviour and cyclic degradation characteristics of composite members. The generated model is first validated against available experimental results then used to investigate the influence of important parameters affecting the moment‐rotation relationships at the dissipative composite beam ends under cyclic loading. Based on the results, nonlinear relationships for modelling the response of composite members are proposed. It is shown that the degradation modelling parameters are most influenced by the cross‐section slenderness of the structural steel and the depth of the composite beam. Together with significant asymmetry in cyclic behaviour, around 20% higher cyclic degradation is observed in composite members compared to their bare steel counterparts. In addition to providing information required for the seismic design and assessment, the proposed expressions are utilised for the calibration of lumped plasticity models with cyclic degradation suitable for computationally efficient frame‐level analysis. [ABSTRACT FROM AUTHOR]

Performance-based seismic codes ensure proper inelastic behaviour of reinforced concrete frames through capacity design, among others. This strategy relies not only on avoiding brittle failures and providing ductility to plastic hinges but also in their distribution within the frame aimed at a greater number of storeys involved in the eventual collapse mechanism. Although codes are generally in agreement to some basic principles in order to ensure capacity design, they show some discrepancies regarding the specific strategies. In this paper, capacity design provisions proposed by some European current codes—Eurocode 8, Italian NTC, and Spanish NCSE-02—are compared, and their effectiveness is discussed. The alternative formulation proposed by Italian code for "strong column–weak beam" turns out to be not suitable under specific circumstances, such as with large gravity loads or significant cantilever deformation in lower storeys. Regarding the value of axial load in columns to be considered for the calculation of shear and moment capacities, provisions in the three codes could eventually cause unconservative design for perimeter columns. The Spanish whole set of provisions is proved to not be effective due to their different fundamentals—they are based on overstrength instead of capacity. For all the three cases, some alternative procedures are suggested in this work. [ABSTRACT FROM AUTHOR]

A probabilistic seismic loss assessment of RC high-rise (RCHR) buildings designed according to Eurocode 8 and located in the Southern Euro-Mediterranean zone is presented herein. The loss assessment methodology is based on a comprehensive simulation approach which takes into account ground motion (GM) uncertainty, and the random effects in seismic demand, as well as in predicting the damage states (DSs). The methodology is implemented on three RCHR buildings of 20-story, 30-story and 40-story with a core wall structural system. The loss functions described by a cumulative lognormal probability distribution are obtained for two intensity levels for a large set of simulations (NLTHAs) based on 60 GM records with a wide range of magnitude (M), distance to source (R) and different site soil conditions (SS). The losses expressed in percent of building replacement cost for RCHR buildings are obtained. In the estimation of losses, both structural (S) and nonstructural (NS) damage for four DSs are considered. The effect of different GM characteristics (M, R and SS) on the obtained losses are investigated. Finally, the estimated performance of the RCHR buildings are checked to ensure that they fulfill limit state requirements according to Eurocode 8. [ABSTRACT FROM AUTHOR]

The effect of an intensity measure's (IM's) sufficiency property on the probabilistic assessment of reinforced concrete (RC) structures due to floor-to-floor structural pounding conditions is examined. In the first part of this investigation, efficiency and sufficiency properties of 23 scalar IMs are verified. Then, the magnitude Mw and the distance Rrup are examined as elements in a vector with an efficient scalar IM to evaluate whether they have any significant effect on the structural response. Subsequently, probabilistic seismic demand models (PSDMs) are developed using linear regression analyses based on a scalar IM and a vector-valued IM. Fragility curves are developed based on these PSDMs, and the influence of Mw and Rrup on the evaluation of the minimum required separation gap distance dg,min due to the pounding effect is examined. More than two hundred nonlinear time history analyses are performed based on the Cloud Analysis method. Seismic displacement demands that control of the global state of the structure, as well as the probability of structural pounding, are examined. The results of this research indicate that once Mw or Rrup is increased, fragility curves are shifted to greater values of IM, and the probability of the exceedance of a certain performance level is reduced. Also, the predictive power of Rrup seems to be greater than the one of Mw. On the other hand, it is revealed that Mw and Rrup induce variabilities in the demand solutions for adequate separation gap distance between the adjacent structures. Therefore, variation in Mw or Rrup may lead, in some cases, to unacceptable evaluations of the pounding effect in the capacity levels of structures. [ABSTRACT FROM AUTHOR]

In this paper, we present a systematic GIS-based approach for producing updated, upscaled, unified and reevaluated maps for the Ionian Islands of Greece, which is an area of great geological interest. In particular, Cephalonia and Lefkada are two islands with an increased and intense seismicity. Therefore, a common GIS geodatabase was produced for handling the geoinformation of the area. New upscaled (scale 1:50,000) geotechnical and seismotectonic maps of these islands were produced based on older ones. On the other hand, the corresponding maps of the islands, based on the categories of the Greek antiseismic code and Eurocode 8, were produced in an effort to correlate them. Beyond that, all the available isoseismal maps of the earthquakes that hit the Ionian Islands were gathered in an effort to evaluate them and to find possible correlations with the other types of maps. Based on the correlation results, the consideration of the Vs30 parameter in the Greek antiseismic code is proposed for a better categorization of the geological formations. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to propose a practical approach for considering the soil – shallow foundation – superstructure interaction effect in nonlinear seismic analysis. Soil structure interaction is a complicated task dealing with various engineering problems. Taking into account the soil structure interaction extends beyond the numerical analysis, geotechnical investigation, or structural design fields. The artistry of considering the soil structure interaction effect lies in the balance between incorporating soil conditions and the superstructure into one collective model. Following this methodology alongside classical soil mechanics principles provides additional confidence to the structural engineering society in adopting a complete practical concept. The herein presented study introduces a fiber macroelement that represents the soil beneath shallow foundations. This allows for the direct utilization of the fiber macroelement in nonlinear pushover and dynamic analysis in commercial software, as well as its simple implementation in open software systems. The introduction of a procedure for forming the stiffness matrix of the element and a hysteresis soil model is also a key component. Special attention is devoted to obtaining the material backbone curve through experimental results and Eurocode 8’s procedures. Furthermore, this paper demonstrates the implementation of a macroelement for considering the soil-structure interaction effect in nonlinear seismic analysis within commercial software. The primary aim is to provide structural designers with a streamlined approach for incorporating soil conditions into superstructure analysis. Numerical analysis results from an example building with a reinforced concrete structure in commercial software highlight the significance of not underestimating soil conditions. This work emphasizes that relying solely on fixed models in everyday structural design could lead to dangerous and unexpected consequences.

In today's time, most seismic design codes are based on a linear elastic force-based approach that includes the nonlinear response (ductility and overstrength) of the structure through a reduction factor (named behavior factor q in Eurocode 8 [EC8]). However, the use of a prescribed q-factor that is constant for a given structural system may fail in providing structures with the same risk level. This paper focuses on the estimation of actual values of q-factor for X-braced steel frames (XBFs) designed according to the European codes and comparing these values to those suggested in EC8. For this purpose, a nonlinear pushover analysis has been performed. The effects of specific parameters, such as the stories number, the brace slenderness ratio, the local response of structural members, and the support type, are evaluated. The results show that the most important parameter that affects the q-factor is the brace slenderness ratio, while the support type has less effect on this factor. Furthermore, a local strength criterion has been proposed to implicitly ensure that the suggested value of the q-factor is conservative.

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]

Summary: This paper presents a new approach to the project of steel buildings, mainly focused on the architectural, structural, and seismic design of stairs. The objective is to design a structural stair system capable of controlling seismic damage and contributing to the bracing system of the building. The article begins with a review of the seismic standard (ATC, FEMA, and EC8) on which the current design criteria for new buildings with stairs are based. The research is based on two spatial building models (A–B) with the same bracing elements but placed differently. Reference Model A follows classical design approaches. It means, stairs are considered nonstructural elements that do not influence the seismic behavior of the building. This structure corresponds to typical braced frames (IV‐CBF and EBF) according to EC8. Model B includes a stair system designed to help control the effects of inter‐story drifts and inertia forces. In this case, the same bracing elements of Model A were integrated into the stair structure of Model B. A comparative seismic behavior analysis of typically braced frames (A) versus specially braced stairs (B) is presented. The research was based on the static nonlinear (pushover) analysis and the capacity spectrum method (ATC‐40) according to the seismic performance levels (FEMA) and damage limitation (EC8). Finally, the braced stairs was verified via nonlinear time‐history analysis in order to better capture the structural safety of the evacuation routes and their influence on the behavior of the building. This deterministic analysis of the braced stairs verified satisfactory results compared to reference bracing systems. [ABSTRACT FROM AUTHOR]

Masonry has been widely used for the construction of residential buildings in Serbia and the majority of European countries. Confined masonry (CM) is a contemporary masonry technology that consists of load-bearing masonry walls enclosed in lightly reinforced horizontal and vertical reinforced concrete (RC) confining elements. CM has been widely used for the construction of low-rise and mid-rise residential buildings in Serbia and the region (Yugoslavia) since the 1960s. The design case study of a typical multi-family residential building located in Niš, Serbia (the third-largest urban center in the country), is discussed in this paper. This building was initially designed as a five-story CM structure in accordance with the 1981 Yugoslav seismic design code PTN-S, which was enforced in Serbia until 2019, when the Eurocode was adopted for official seismic design codes. Due to architectural constraints, the original design solution involving the CM system was not compliant with the code; hence, an alternative design using an RC-frame system with masonry infills was adopted. A comparison of two different design solutions provides insight into the different requirements of seismic design codes that have been used in the region. It is important to observe that seismic forces for RC structures determined in accordance with the PTN-S code are considerably lower compared to the ones determined according to EC 8-1, with the ratio ranging from 0.37 to 0.69. The seismic shear force according to Eurocode 8 is 1.46 times higher than the force that was used for seismic design according to the PTN-S code in the case of RC-frame structures. The results of an analysis of CM structures show that the seismic shear force in accordance with Eurocode 8 is almost 2.6 times higher than the force that was used for seismic design in accordance with the PTN-S code. The findings of this study are believed to be useful for understanding the difference in seismic design solutions for previous seismic design codes (which were used in the region for more than 40 years) and the present codes (Eurocodes).

Steel frames equipped with chevron bracing (Λ-CBF) are usually less ductile than other steel systems. Therefore, in many cases, it can be convenient to design Λ-CBF to exploit their stiffness and resistance to enforce a pseudo-elastic seismic response of the building in low to moderate seismic zones. In current EC8, the rules for moderate Λ-CBF are the same as those for high ductile frames, thus potentially leading to massive, over-resistant and uneconomic systems. In the next version of EC8 new rules have been set to design moderate ductile Λ-CBF, aiming to enhance the ease of use of the code as well as to obtain less expensive structures. The new rules of the updated EC8 are based on local requirements and elastic calculation without any plastic analysis. This paper discusses these rules that are numerically investigated by means of nonlinear static analyses on a set of 8-storey steel frames designed for different seismic intensities. The performed analyses show that the frames designed according to the updated EC8 exhibit moderate ductility, preventing damage to brace-intercepted beams and reducing ductility demand on braces under compression. [ABSTRACT FROM AUTHOR]

• Formulas for the shear resistance evaluation of wood panel-to-steel sheet screw connections has been calibrated based on a wide experimental database. • The Easley et al. [1] method has been validated for shear walls with wood sheathing covered by 2nd-generation of Eurocode 8 on the bases of a wide experimental database. • The partial safety factor for in-plane horizontal resistance evaluation of shear walls with wood sheathing has been defined according to the limit state design within the Eurocode format. • The overstrength factor for SWWS belonging to Ductility class 3 (DC3) according to prEN1998-1-2 (CEN, 2022) [2] has been derived according to the capacity design within the Eurocode format. Within the 2nd-generation of Eurocodes several new lateral force resisting systems (LFRS) typically used in lightweight cold-formed steel (CFS) buildings have been introduced, including shear walls with wood sheathing (SWWS). Therefore, extensive studies have been carried out to define the seismic design parameters according to the format of European code for seismic design, i.e. Eurocode 8. In current version of the 2nd-generation Eurocode 8 (prEN1998-1-2, CEN 2022), in case of SWWS the behaviour factor has been defined based on the FEMA P695 (FEMA, 2009) [3] methodology, whereas the other seismic design parameters have been set based on assumption validated with analyses on limited case studies. To overcome this lack, specific research devoted to defining the main seismic design parameters for SWWS belonging to Ductility class 3 (DC3) according to prEN1998-1-2 (CEN 2022) has been carried out at the University of Naples "Federico II". The research shows that the Easley et al. (1982) method gives consistent in-plane horizontal wall resistance predictions if the shear resistance of wood panel-to-steel sheet screw connections (sheathing connections) is evaluated with reliable approaches and formulas for the evaluation of the shear resistance of sheathing connections have been calibrated. Based on the results obtained from this research, a partial safety factor for resistance evaluation of SWWS according to limit state design (LSD) equal to 1.3 is proposed and an overstrength (expected resistance) factor for the design of non-ductile elements according to capacity design equal to 1.7 is recommended. [ABSTRACT FROM AUTHOR]

Old bridges present several seismic vulnerabilities and were designed before the emergence of seismic codes. In this context, partial seismic isolation has given a special attention to improve their seismic performance. In particular, elastomeric bearings are the simplest and least expensive mean for this, enabling to resist both non-seismic actions and earthquake loads. In order to assess the initial structural performance and the improvement done by the isolation, this paper attempts to combine multi objective optimization using genetic algorithms with linear and non-linear analysis using FE program OpenSees. A prior screening of the columns states is settled and then a multi objective optimization of a population of standard sized bearings meeting non-seismic and stability requirements is established to optimize the linear and non-linear behavior of the structure, finding the best compromise between displacements and forces at the columns

Earthquake records indicate that earthquake motion is an irregular oscillatory soil movement as a consequence of the heterogeneity of the soil material, as well as due to reflection, refraction, and interference of seismic waves. The trajectories of soil particle movement during an earthquake are proven to be chaotic, so the approximation of seismic effects by a simplified collinear model is very rough from an engineering point of view. The directions of the earthquake during the duration of the earthquake event affects the results of the seismic calculation. In this paper, the simultaneous influence of horizontal seismic load components on buildings has been analyzed. Actual seismic norms deal with this issue and define recommendations that should be applied in the design. This paper discussed how realistic and applicable these recommendations are in standard engineering design. A series of time history analyses of the horizontal stiffness of reinforced concrete regular and irregular structures were performed. Two earthquake events with a markedly changing direction of the ground acceleration vector were taken as the load. Significant differences in the influence values of the adopted representative parameters were determined for the two considered cases of collinear and simultaneous effects. In the conclusion, a critical review of the usual seismic calculation and the provisions of Eurocode 8, related to the effect of the horizontal components of the seismic load, is given. Finally, the paper comments on the introduction of corrective factors in cases where simultaneous action is not considered.

A simple methodology for seismic assessment of masonry building, which allows the ranking of the seismic safety of buildings according to principles and rules that are established in Part 3 of the Eurocode 8 (EC8), is presented in this work. This approach uses the concept of "performance curve", which consists in the representation of all possible performance points (the target displacements of the EC8) associated with a given capacity curve and a response spectrum. This allows a better comparison of the overall seismic behaviour, namely a comparison of the seismic safety associated with all limit states at once, which makes the task of ranking the urgency for seismic retrofitting measures easier. This methodology was used for ranking a set of primary school masonry buildings that still exist in the region of Algarve (Portugal). This work was carried out in the context of the PERSISTAH project. [ABSTRACT FROM AUTHOR]