Eurocode 8 (EC8) allows the use of dynamic analysis for the design and assessment of structures and provides some constraints for the selection of acceleration time-histories as seismic input. ...However, when it comes to the selection of two-horizontal-component natural ground motion records, parts 1 and 2 of EC8, stipulate apparently different criteria. The first aim of this paper is to build up on previous studies and investigate whether this difference in provisions translates into the selection of systematically different sets of records. A series of record selection case-studies presented in this study, corroborate the preliminary findings of previous work, and show that this is not the case, that is, record sets chosen according to one group of criteria tend to satisfy the other by default. A second aim is to investigate the different options for selecting multi-component ground motion records in part 1, which turn out to be equivalent. Finally, a third issue tackled is the effect that different definitions of spectral acceleration, that the design spectrum refers to, can have on spectrum-compatible record selection, when two horizontal components are involved. The results indicate that, for some of these alternative definitions, such as maximum or random component spectral acceleration, sets obtained via direct spectrum compatibility may not always agree with a simple application of Eurocode 8 provisions. On the other hand, when spectral acceleration is defined as the geometric mean of the two components, consolidated record selection algorithms appear to guarantee spectrum compatibility.
•Presentation of an open-source, graphical user interface for OpenSees.•The software performs dynamic analysis of yielding single-degree-of-freedom systems subjected to accelerograms.•Incremental ...dynamic, multi-stripe and cloud analysis are supported.•Post-processing routines render the software a tool for performance-based earthquake engineering.•Examples of probabilistic seismic demand analysis are provided.
Non-linear dynamic response of SDOF systems enjoys widespread application in earthquake engineering, sometimes as a testing ground for cumbersome analytical procedures, but often as a direct proxy of first-mode-dominated structures, within the family of simplified, pushover-based methods for seismic structural assessment and/or design. This article presents DYANAS, a MATHWORKS-MATLAB®-based graphical user interface that uses the OpenSees finite element platform to perform nonlinear dynamic analysis of single-degree-of-freedom (SDOF) oscillators. The scope of this open-source, freely distributed software is to serve as a tool for earthquake engineering research. The main advantages offered by the DYANAS interface are ease in the definition of the required analysis parameters and corresponding seismic input, efficient execution of the analyses themselves and availability of a suite of convenient, in-built post-processing tools for the management and organization of the structural responses. The types of dynamic analysis frameworks supported are incremental, multiple-stripe and cloud. Simultaneous consideration of pairs of uncoupled dynamic systems gives the possibility for intensity measures to refer to bidirectional ground motion. In the paper, an outline of the types of dynamic analysis frameworks typically used in performance-based earthquake engineering is provided, followed by a detailed description of the software and its capabilities, that include an array of post-processing tools. In order to properly place this software tool within its natural performance-based earthquake engineering habitat, some example applications are provided at the end of the paper.
On the night of February 6, 2023, a major earthquake struck Turkey and nearby Syria, whose moment magnitude (M) was estimated at 7.8 (or 7.7, depending on the data source). It started what can be ...considered a seismic sequence with thousands of recorded earthquakes with magnitude larger than two, including another M6.7 event (or 6.6) occurring shortly after, and one M7.5 (or 7.6) a day and a half later. The area in the south‐eastern part of Turkey hit by the sequence is considered, according to probabilistic models, one of the most hazardous in the wider region. This technical note aims at a preliminary illustration of some features of the shaking, deemed of earthquake engineering relevance. To this aim, it preliminarily analyzes the evolution of the sequence so far and the related ground motion intensity, as estimated from ShakeMap envelopes, then focuses on the largest magnitude event, for which a preliminary model of the source is available, while a supplementary report is provided for the other two events. Based on data available at the time of writing, it is found that the development of the sequence and the recorded ground motions are generally in agreement with available models, although some locations may have experienced peak ground accelerations larger than 1.0 g, and near‐source effects, determining pulse‐like ground motions, apparently occurred.
Structural reliability assessment for a building that may experience damage accumulation during a seismic sequence can play an important role in decision making for post-earthquake repair operations ...or demolition and rebuilding. This typically requires the integration of the aftershock ground motion hazard at the site with the probabilistic description of the damaged building's capacity to withstand the shaking of the seismic sequence. This is usually quantified as the conditional probability that the structure, starting from a specific damage state and for given shaking intensity, will reach a more severe one. In sequence-based seismic risk studies, an analytically-derived estimate of the peak inelastic displacement is often used as a proxy for structural damage. This paper investigates the issues behind this choice and the ability of inelastic displacement demand to adequately describe structural damage due to a seismic sequence, when compared with more direct metrics of damage, such as stiffness and strength degradation. To reach this objective, a series of inelastic single-degree-of-freedom systems, having different natural period, backbones and post-elastic behavior, were subjected to sequential dynamic analysis, while considering a series of arbitrarily chosen damage states, conventionally defined by displacement demand thresholds. The investigation showed that maintaining the attractive simplicity of deformation-based damage proxies in sequence-based risk analysis, can lead to some counterintuitive representations of seismic vulnerability. Some results suggest that such problems could be alleviated if one were to consider some dependence of damage state transition thresholds on the current state of the structure.
In state‐of‐the‐art building codes, the traffic loads for the design or assessment of bridges should derive from a probabilistic characterization. However, because traffic depends on the vehicle flow ...peculiar to the transportation infrastructure of interest, the frequency of exceedance of code‐assigned loads is factually unknown. This study presents a methodology to probabilistically characterize the traffic loads on bridges based on network‐level traffic micro‐simulation and its application to the A56, that is, the urban highway connecting Naples’ (Italy) districts. One year of traffic simulations, in conjunction with structural modeling of the bridges featured in the infrastructure, enabled the probabilistic characterization of the traffic‐induced structural demand and the determination of the bridge‐specific safety margins along the highway. The results of the study and of the application to A56 ultimately show that: (i) traffic micro‐simulation appears to be a suitable approach to bridge‐specific structural safety assessment; (ii) structural actions deriving from code‐assigned loads tend to be conservative with respect to their traffic‐simulation‐derived counterparts; and (iii) structural demand induced by traffic loads can vary along the same transportation infrastructure.
The central Italy seismic sequence began in the latter half of 2016 and continued well into 2017, causing severe damage in the villages close to the source and causing hundreds of casualties. It is a ...sequence especially interesting to study, from the perspective of seismic actions experienced by structures, because it saw nine M ≥ 5.0 earthquakes within a period of 5 months, rupturing parts of the complex central Apennine mountain range fault system. Consequently, some of the main earthquake engineering issues that arose are the multiple locations where the code-mandated seismic actions were exceeded in more than one of the main events of the sequence and the number of pre- and low-code existing buildings that suffered heavy damage or collapse due to the intensity of individual earthquakes and the cumulative effect of repeated damaging shocks. The present article picks up on these topics and uses probabilistic seismic hazard, as well as the multitude of strong ground motion recordings available from the sequence, to provide a discussion on certain issues, that are all related to the topical subject of seismic actions. These issues are: (1) the unsurprising exceedance of code spectra in the epicentral areas of strong earthquakes; (2) the particular spectral shape and damaging potential of near-source, pulse-like, ground motions, possibly related to rupture directivity; and (3) structural non-linear behaviour in the wake of a sequence that produces repeated strong shaking without the necessary respite for repair and retrofit operations.
The dynamic behaviour of rigid blocks subjected to support excitation is represented by discontinuous differential equations with state jumps. In the numerical simulation of these systems, the jump ...times corresponding to the numerical trajectory do not coincide with the ones of the given problem. When multiple state jumps occur, this approximation may affect the accuracy of the solution and even cause an order reduction in the method. Focus here is on the error behaviour in the numerical dynamic. The basic idea is to investigate how the error propagates in successive impacts by decomposing the numerical integration process of the overall system into a sequence of discretized perturbed problems.
Abstract
Seismic reliability assessment of selected bridge structures code‐conforming with respect to the current Italian practice is carried out. Two viaducts, tall and shallow, and two highway ...overpasses, with traditional seat‐type or integral abutments, are considered. Each structure is ideally placed at three reference sites, that is, Milan, Naples and L'Aquila, characterised by low, moderate and high seismic hazard, respectively. At each site, a soil profile representative of typical local conditions is defined for foundation design, site response analysis and soil‐structure interaction modelling. Probabilistic seismic hazard is used in conjunction with multiple‐stripe non‐linear dynamic analysis, featuring conditional‐spectrum compatible ground motions, to establish the failure rate with respect to two purposely defined and functionality‐related performance levels. It is confirmed the decreasing seismic reliability with increasing design seismic action, already observed for other structural types, and it is shown that integral abutment overpasses tend to be more reliable than traditional ones, even seismically isolated ones. The results are of larger interest given the closeness of the Italian code to the Eurocode.
