Eurocode 8 is undergoing a thorough revision process encompassing a significant number of changes. In this work, the novel ductility classes, drift limits for damage limitation, local ductility ...conditions, and corresponding detailing prescriptions are presented and discussed. It is paramount to analyse and contrast these modifications with the current provisions of Eurocode 8. In order to assess the impact of such revisions, an extensive examination was conducted on ten symmetrical moment-resisting frame (MRF) buildings. These buildings are regular in plan and in elevation and are not torsionally flexible. The analysis was carried out following both the current and the second-generation Eurocode 8 provisions, with the results being compared in order to evaluate the effectiveness of the new design and detailing provisions. The study outcomes revealed that the DCM, DC2, and DC3 structures demonstrated different trends in their detailing demands for local ductility and capacity design. Differences in reinforcement quantities were observed between DCM and DC2, as well as DC2 and DC3, for 5-storey and 10-storey buildings. The design approach focused on individual member detailing requirements, to optimize design, while maintaining the overall concrete quantities. These insights offer valuable economic considerations for various structural configurations under strong seismic actions.
•The comparison between DCM - DC2 and DC2 - DC3, shows variations in the longitudinal and transverse reinforcement.•Buildings designed for DCM and DC3 ductility classes behave similarly.•There is a consistent linear trend where capacity design in shear exceeds seismic design demand for all ductility classes.•Capacity design in shear is generally higher than seismic design demand, indicating adequate shear resistance.•Some columns show substantially higher values, possibly due to higher moment values at lower storeys.
This paper is aimed to discuss the conceptual troubles currently appearing in the codified rules to account for second-order effects in the seismic design of structures. First of all, starting from ...SDOF systems, the distinction between second-order effects in the elastic range and second-order effects in the plastic range is clarified. Moreover, the attention is focused on the conceptual difference occurring between a parameter measuring the structural proneness to second-order effects and a demand parameter measuring the safety level against the phenomenon of dynamic instability. Successively, the critical issues concerning the behaviour occurring in real MDOF structures when compared to SDOF systems is pointed out underlining the uncoupling between second-order effects in the elastic range and second-order effects in the plastic range, due to the influence of the collapse mechanism typology. The codified rules to account for second-order effects in Eurocode 8 are analysed showing why they are conceptually wrong giving rise to a lot of unjustified problems in the seismic design of steel MRFs. Recent proposals to improve Eurocode 8 are also analysed. Finally, it is shown how relevant studies already existing in the technical literature can be exploited in order to set up code provisions having a sound theoretical background. Finally, a new proposal, accounting for the influence of the collapse mechanism, for codification of P − Δ effects in seismic design is presented.
●In the case of SDOF systems, the stability coefficient is the only one parameter needed to measure the structural proneness to second-order effects both in the elastic range and in the plastic range.●The stability coefficient adopted by Eurocode 8 is not a parameter measuring the structural proneness to second-order effects.●Dynamic instability is a phenomenon related to the seismic displacement demand.●In the case of real MDOF structures, the structural proneness to second-order effects in the plastic range of behaviour is dependent on the collapse mechanism.●A new proposal for codification of effects in seismic design is proposed.●The proposal novelty is that it accounts for the need of amplifying the seismic design forces, directly accounting for the influence of the collapse mechanism typology.
•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.
Steel moment resisting frames (MRFs) are drift‐sensitive structures and their design is largely influenced by code requirements to limit the lateral displacements and to control the second order ...effects. Current and next generation of Eurocode 8 recommend different rules to verify the lateral rigidity and resistance of steel MRFs that lead to structures that are substantially different in terms of size of members and overall performance. In order to investigate the influence of the design rules on the seismic behaviour of ductile steel MRFs a parametric numerical study was carried out on 48 structures designed according to Eurocodes as well as US codes, the latter analysed as benchmark, varying the number of storeys, moment resisting spans and seismic intensity. The results of non‐linear static and dynamic analyses show that the structures complaint with current Eurocode 8 are the most expensive and characterised by the greater lateral rigidity and resistance, while MRFs designed in accordance with ASCE7 rules have the smaller profiles and the lower overstrength. The frames designed with rules of the latest version of next generation of Eurocode 8 have an intermediate behaviour even if closer to ASCE7‐compliant structures. These results are also confirmed by the probability of collapse that is smaller than the minimum value specified by EN1990 for the considered consequence class of the examined buildings.
Eccentrically braced frames (EBFs) constitute a good structural solution located between Moment Resisting Frames (MRFs) and Concentrically Braced Frames (CBFs) because they exhibit an adequate ...lateral stiffness joined with a high ductility capacity, especially for what concerns short and very short links. Link design plays an important role in the effective dissipation capacity of the structure that is well designed only if the link members are involved in plastic range while the other members remain elastic. A proper design of the non-dissipative members needs to account for the link overstrength that results to be very high, especially for very short links.
In this paper, the influence of the axial restraints on the evaluation of the link overstrength and ultimate rotation is investigated. A wide parametric analysis is carried out based on a set of shapes selected in the European Standards. FEM simulations are used to develop the parametric analysis after a calibration carried out on experimental tests selected from a literature review. Empirical formulations are also proposed with the scope of providing a more accurate evaluation of the overstrength factor for short and very short links in the framework of EU “I shaped” standard profiles.
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•Numerical analyses of detailed finite element models (FEM) are carried out.•The effect of axial restraint on the plastic overstrength and ultimate rotation of EBF EU “I shaped” links is investigated.•A parametric analysis is reported to set up more accurate relations to evaluate the overstrength factor.•Overstrength factor formulations are proposed for both short and very short link, with and without the axial restraint.•The proposed formulations have partial safety coefficients to account for the model uncertainty.
The catastrophic effects of recent earthquakes around the world have highlighted the vulnerability of civil buildings; in Europe, most of the existing buildings were built after World War II and ...since they have largely exceeded their useful life, are characterized by a high vulnerability linked both to the durability of the materials and to the lack of seismic provisions in design. The current trend in constructional field is to design interventions aimed at the seismic and energy improvement of these structures jointly, in order to achieve a sustainable and integrated retrofit intervention. To this aim, the use of 2D orthogonal steel exoskeletons for the seismic strengthening represents a suitable solution, providing at the same time an enhancement in thermal insulation, through a ‘double-skin’ solution. Due to the growing interest in the design of steel exoskeleton interventions, a detailed dynamic characterization of this external strengthening solution is needed. In this framework, the present work, aims to investigate the effectiveness of the investigated strengthening solution by means of bi-directional non-linear dynamic analyses. Extensive numerical analysis was carried out. The selected case-study is an Italian existing pre-1980 s RC frame building located in Mugnano di Napoli (NA, Italy), which is a medium-high seismic hazard site in Italy (peak ground acceleration equal to 0.156 g). Two alternative strengthening solutions were numerically investigated by means of non-linear time-history and incremental dynamic analyses performed applying fifteen bidirectional ground motions on three-dimensional numerical models. The results of the dynamic non-linear analyses allow to quantify more appropriate performance indicators, both in terms of expected demand and overall collapse capacity, useful for the development of optimization strategy and design of exoskeleton system. The results highlighted that both the investigated strengthening scenarios allow to increase the stiffness of the existing building and allow it to meet the current code safety requirements reducing also the residual inter-storey drift. The obtained results are not strictly related to the investigated case study, but can be extended to all the structures retrofitted that follows the presented design procedure.
•The catastrophic effects of recent earthquakes around the world have highlighted the vulnerability of civil buildings.•Due to the interest in the design of exoskeleton, a dynamic characterization of this strengthening solution is needed.•The strengthening of an existing RC structure with EXO-S-2D placed orthogonally to the building façade is presented.•The efficiency of a displacement-based design procedure is validated by means of static and dynamic non-linear analyses.•The results of the dynamic non-linear analyses allow to quantifyperformance indicators of the strengthened intervention.
The 2013 European Seismic Hazard Model (ESHM13) results from a community-based probabilistic seismic hazard assessment supported by the EU-FP7 project “Seismic Hazard Harmonization in Europe” (SHARE, ...2009–2013). The ESHM13 is a consistent seismic hazard model for Europe and Turkey which overcomes the limitation of national borders and includes a through quantification of the uncertainties. It is the first completed regional effort contributing to the “Global Earthquake Model” initiative. It might serve as a reference model for various applications, from earthquake preparedness to earthquake risk mitigation strategies, including the update of the European seismic regulations for building design (Eurocode 8), and thus it is useful for future safety assessment and improvement of private and public buildings. Although its results constitute a reference for Europe, they do not replace the existing national design regulations that are in place for seismic design and construction of buildings. The ESHM13 represents a significant improvement compared to previous efforts as it is based on (1) the compilation of updated and harmonised versions of the databases required for probabilistic seismic hazard assessment, (2) the adoption of standard procedures and robust methods, especially for expert elicitation and consensus building among hundreds of European experts, (3) the multi-disciplinary input from all branches of earthquake science and engineering, (4) the direct involvement of the CEN/TC250/SC8 committee in defining output specifications relevant for Eurocode 8 and (5) the accounting for epistemic uncertainties of model components and hazard results. Furthermore, enormous effort was devoted to transparently document and ensure open availability of all data, results and methods through the European Facility for Earthquake Hazard and Risk (
www.efehr.org
).
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.
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.
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