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A cloud method for generating percentile engineering demand parameter versus intensity measure (EDP-IM) curves of a structure subjected to a set of synthetic ground motions is presented. To this end, an ensemble of synthetic ground motions based on available real ones is generated. This is done by using attenuation relationships, duration and suitable Gutenberg-Richter relations attributed to the considered seismic hazard at a given site by estimating a suitable distribution of magnitude and site to source distance. The study aims to clarify the significance of the duration and frequency content on the seismic performance of structures, which were not considered in developing percentile incremental dynamic analysis (IDA) curves. The collapse probabilities of two steel moment-resisting frames with different ductility levels generated by IDA and the proposed cloud method are compared at different intensity levels. When compared with conventional IDA, the suggested cloud analysis (SCA) methodology with the same run number of dynamic analyses was able to develop response hazard curves that were more consistent with site-specific seismic hazards. Eliminating the need to find many real records by generating synthetic records consistent with site-specific seismic hazards from a few available recorded ground motions is another advantage of using this scheme over the IDA method.. [ABSTRACT FROM AUTHOR]

In Europe, computation of displacement demand for seismic assessment of existing buildings is essentially based on a simplified formulation of the N2 method as prescribed by Eurocode 8 (EC8). However, a lack of accuracy of the N2 method in certain conditions has been pointed out by several studies. This paper addresses the assessment of effectiveness of the N2 method in seismic displacement demand determination in non-linear domain. The objective of this work is to investigate the accuracy of the N2 method through comparison with displacement demands computed using non-linear time-history analysis (NLTHA). Results show that the original N2 method may lead to overestimation or underestimation of displacement demand predictions. This may affect results of mechanical model-based assessment of seismic vulnerability at an urban scale. Hence, the second part of this paper addresses an improvement of the N2 method formula by empirical evaluation of NLTHA results based on EC8 ground-classes. This task is formulated as a mathematical programming problem in which coefficients are obtained by minimizing the overall discrepancy between NLTHA and modified formula results. Various settings of the mathematical programming problem have been solved using a global optimization metaheuristic. An extensive comparison between the original N2 method formulation and optimized formulae highlights benefits of the strategy. [ABSTRACT FROM AUTHOR]

Recent earthquakes have revealed that conventional seismic design philosophy allows for large levels of nonstructural damage. Nonstructural earthquake damage results in extensive repair costs and lengthy functional disruptions, as nonstructural systems comprise the majority of building investment and are essential to building operations. A better understanding of the expected overall seismic performance of code-compliant buildings is needed. This study investigates the seismic performance of a conventional building. A 16-storey steel office building was designed using a modern seismic structural code (Eurocode 8). This study is the first to assess in detail the substantial earthquake repair costs expected in a modern Eurocode concentric braced frame structure, considering nonstructural systems with the FEMA P-58 procedure. The breakdown of total repair costs by engineering demand parameter and by fragility group is novel. The seismic performance assessment indicated that substantial earthquake repair costs are expected. Limitations of the Eurocode nonstructural damage methodology were revealed in a novel manner using FEMA P-58, as the prescribed drift limits did not minimize nonstructural repair costs. These findings demonstrate the need for design procedures that improve nonstructural seismic performance. The study results provide a benchmark on which to evaluate retrofit alternatives for existing buildings and design options for new structures. [ABSTRACT FROM AUTHOR]

Timber constructions have been widely suggested to be seismically resistant based on post-disaster reconnaissance studies. This observation has, however, remained to a large extent anecdotal due to the lack of experimental work supporting it, especially for certain timber architectural forms, including traditional timber frame ' hımış' structures. To fill this gap, the authors carried out an extensive full-scale testing scheme using frames of various geometrical configurations, tested under reverse-cyclic lateral loading with/without infill (brick and adobe) or cladding ( bağdadi and şamdolma) (Aktas et al. in Earthq Spectra 30(4):1711-1732, 2014a, b). The tests concluded that hımış frames had high energy dissipation capabilities due mostly to nailed connections. Infill/cladding significantly helped improve stiffness and lateral load strength of the frames, and timber type did not seem to make a remarkable impact on the overall behaviour. The current paper, on the other hand, uses test data to calculate capacity/demand ratios based on capacity spectrum method and Eurocode 8 to elaborate more on the performance of ' hımış' structures under seismic loading. The obtained results are discussed to draw important conclusions with regards to how frame geometry and infill/cladding techniques affect the overall performance. [ABSTRACT FROM AUTHOR]

Nonstructural components (NSCs) should be subjected to a careful and rational seismic design, in order to reduce the economic loss and to avoid threats to the life safety, as well as what concerns structural elements. The design of NSCs is based on the evaluation of the maximum inertia force, which is related to the floor spectral accelerations. The question arises as to whether Eurocode 8 is able to predict actual floor response spectral accelerations occurring in structures designed according to Eurocode 8. A parametric study is conducted on five RC frame structures in order to evaluate the floor response spectra. The structures, designed according to Eurocode 8, are subjected to a set of earthquakes, compatible with the design response spectrum. Time-history analyses are performed both on elastic and inelastic models of the considered structures. Eurocode formulation for the evaluation of the seismic demand on NSCs does not well fit the numerical results. Some comments on the target spectrum provided by AC 156 for the seismic qualification of NSC are also included. [ABSTRACT FROM AUTHOR]

The seismic behavior of flat-bottom silos containing grain-like material still presents strong uncertainties and current design codes tend to provide too conservative formulations for the estimation of the seismic actions. Over the years, some researchers focused on the dynamic behavior of such silos mainly through numerical investigations. Analytical formulations for the evaluation of the pressures exerted by the ensiled grain on the silo wall under seismic excitation were developed by Younan and Veletsos (J Struct Eng ASCE 124(1):62-70 ) and, more recently, by Silvestri et al. (Bull Earthq Eng 10(5):1535-1560 ). Experimental shaking-table tests were performed on silo specimens (Silvestri et al. EESD , submitted), which showed good agreement with the Silvestri's analytical formulations, even if some theoretical limits of validity were not satisfied. This has encouraged a complete revision and refinements of the theoretical framework, which is the object of this paper. In detail, the static and the dynamic actions exchanged between different grain portions and between the grain and the silo wall are idealised in a more physically consistent way. The analytical developments are carried out by means of simple free-body dynamic equilibrium equations. The refinements yield to a significant extension of the theoretical limits of validity and to a new set of analytical formulas for the wall pressures and for the wall shear and bending moment. A comparison of the analytical formulas with (i) the consolidated Janssen (Zeitschrift des vereines deutcher Ingenieure 39:1045-1049 ) and Koenen (Centralblatt der Bauverwaltung 16:446-449 ) theory for static design of silos and (ii) with the Eurocode 8 provisions for seismic design of silos and with the experimental results is also performed in order to (i) check the updated theoretical model in static conditions and (ii) verify the reliability of the different formulations in accelerated conditions, respectively. The refined theory confirms that the portion of ensiled material that interacts with the silo wall is significantly smaller than the effective mass suggested by Eurocode 8. [ABSTRACT FROM AUTHOR]

This paper presents the results of a series of shake-table tests on a half-scale, four-storey building with reinforced concrete and unreinforced masonry walls. Due to the lack of reference tests, the seismic behaviour of such mixed structures is poorly understood. The test unit was subjected to several runs of increasing intensity yielding performance states between minor damage and near collapse. Before the test, the expected peak table accelerations leading to different limit states were estimated using the capacity spectrum method, and the predicted values corresponded rather well to actual sustained accelerations. Next to these analyses, the paper describes the test unit, instrumentation and input motion, and comments on the response of the mixed structure in terms of damage evolution and global response quantities, such as force-displacement response and drift and acceleration profiles. The raw and post-processed data sets are made publically available, and all relevant information with regard to data organisation and post-processing procedure is described in an appendix to this paper. The test serves therefore as a benchmark for the validation of numerical models of such mixed structures. The project aims at providing a foundation for the development of seismic design and assessment methods of mixed structures, which are currently not covered by structural codes, including Eurocode 8. [ABSTRACT FROM AUTHOR]

The seismic assessment of existing buildings is an essential issue of seismic engineering. This work is focused on the evaluation of the seismic performance of existing RC buildings according to the current Italian Technical Code, which almost coincides with the European Eurocode 8. Alternative types of analyses, all consistent to the Code provisions, have been performed with reference to a case-study, that is a real RC hospital building. An accurate knowledge of the building has been achieved, as a result of a collaboration between the University of Florence and the Regional Government. Both elastic and inelastic modeling, as well as static and dynamic ones, have been adopted in the analysis. The global response-with special attention to torsional effects-and the seismic performance of each single member have been found with all the performed analyses. The comparison among the analyses has been performed in terms of both global and local response parameters, and the reliability of each analysis has been pointed out. [ABSTRACT FROM AUTHOR]

A ground motion with a PGA of 0.39 g, above the 475-year design earthquake specified in the Greek seismic code and the National Annex to Eurocode 8, was recorded about 100 m from the municipal theatre of Argostoli, the capital of the Ionian island of Kefalonia. The building, the largest in volume in the town, was designed and constructed to the 1959 seismic code for lateral loads (about 30 % of those specified today). Suffering also from severe reinforcement corrosion and poor concrete quality, it provided the ground to apply for the first time (in 2005) Part 3 of Eurocode 8 for seismic assessment and retrofitting. The assessment based on nonlinear dynamic analysis showed that the buidling was deficient even under ground motions with PGA less than 0.05 g. Alongside the need to tackle corrosion, the design of the retrofitting had to face several constraints and requirements: minimal disruption of the facility's operation, accessibility to the foundation only along the building perimeter, no change to the façade and minimal intervention to the other lateral sides. A very cost-effective retrofitting was designed, employing: (a) one-sided RC or fibre-reinforced polymer (FRP) overlays and two new walls at the perimeter, (b) connection of the two structurally independent and torsionally imbalanced units of the building in a single structure, and (c) one-sided FRP jacketing of selected interior elements. Less than 7 years after the works were completed, the building went unscathed through a Magnitude 6.1 earthquake. Serious damage was limited to four nonstructural masonry infill panels at the penthouse, which, according to the retrofit design, could be sacrificed, so as to protect vulnerable structural elements that could not be retrofitted in the first place. Nonlinear dynamic analyses of the response of the retrofitted building to the recorded ground motions are in agreement with the observed performance. They show also that, had the as-built facility not been retrofitted, it might have collapsed in the earthquake. [ABSTRACT FROM AUTHOR]