Incremental dynamic analysis (IDA) is presented as a powerful tool to evaluate the variability in the seismic demand and capacity of non-deterministic structural models, building upon existing methodologies of Monte Carlo simulation and approximate moment-estimation. A nine-story steel moment-resisting frame is used as a testbed, employing parameterized moment-rotation relationships with non-deterministic quadrilinear backbones for the beam plastic-hinges. The uncertain properties of the backbones include the yield moment, the post-yield hardening ratio, the end-of-hardening rotation, the slope of the descending branch, the residual moment capacity and the ultimate rotation reached. IDA is employed to accurately assess the seismic performance of the model for any combination of the parameters by performing multiple nonlinear timehistory analyses for a suite of ground motion records. Sensitivity analyses on both the IDA and the static pushover level reveal the yield moment and the two rotational-ductility parameters to be the most influential for the frame behavior. To propagate the parametric uncertainty to the actual seismic performance we employ (a) Monte Carlo simulation with latin hypercube sampling, (b) pointestimate and (c) first-order second-moment techniques, thus offering competing methods that represent different compromises between speed and accuracy. The final results provide firm ground for challenging current assumptions in seismic guidelines on using a median-parameter model to estimate the median seismic performance and employing the well-known square-root-sum-of-squares rule to combine aleatory randomness and epistemic uncertainty. 143 as a testbed and focusing on the plastic-hinge modeling uncertainties, we will nevertheless present a general methodology that is applicable to a wide range of structures. MODEL DESCRIPTIONThe structure selected is a nine-story steel moment-resisting frame with a single-story basement (Figure 1) that has been designed for Los Angeles, following the 1997 NEHRP (National Earthquake Hazard Reduction Program) provisions [12]. A centerline model with nonlinear beamcolumn connections was formed using OpenSees [13]. It allows for plastic hinge formation at the beam ends while the columns are assumed to remain elastic. This has been a conscious choice on our part: despite the rules of capacity design, there is always the possibility of a column yielding earlier than the connecting beams, an issue aggravated by uncertain yield strengths. Preliminary tests found this effect to be minor for this nine-story structure, especially when high correlation was assumed between the steel strengths of beams and columns.The structural model also includes P − effects while the internal gravity frames have been directly incorporated (Figure 1). The fundamental period of the reference frame is T 1 = 2.35 s and accounts for approximately 84% of the total mass. Essentially this is a first-mode dominated structure that still allows for significant sensitivity to higher modes. Previous studies...

SUMMARYA methodology for the performance-based seismic risk assessment of classical columns is presented. Despite their apparent instability, classical columns are, in general, earthquake resistant, as proven from the fact that many classical monuments have survived many strong earthquakes over the centuries. Nevertheless, the quantitative assessment of their reliability and the understanding of their dynamic behaviour are not easy, due to the fundamental non-linear character and the sensitivity of their response. In this paper, a seismic risk assessment is performed for a multidrum column using Monte Carlo simulation with synthetic ground motions. The ground motions adopted contain a high and a low frequency component, combining the stochastic method and a simple analytical pulse model to simulate the directivity pulse contained in near source ground motions. The deterministic model for the numerical analysis of the system is three dimensional and is based on the Discrete Element Method (3D DEM). Fragility curves are produced conditional on magnitude and distance from the fault and also on scalar intensity measures for two engineering demand parameters (EDPs), one concerning the intensity of the response during the ground shaking and the other the residual deformation of the column. Three performance levels are assigned to each EDP. Fragility analysis demonstrated some of the salient features of these spinal systems under near-fault seismic excitations, as for example their decreased vulnerability for very strong earthquakes of magnitude 7 or larger. The analysis provides useful results regarding the seismic reliability of classical monuments and decision making during restoration process.

3The increased frequency of natural disasters and man-made catastrophes has caused major disruptions to 4 critical infrastructures (CI) such as Water Distribution Networks (WDNs). Therefore, reducing the 5 vulnerability of the systems through physical and organizational restoration plans are the main concern 6 for system engineers and utility managers that are responsible for the design, operation, and protection 7 of WDNs. In this paper, a Resilience Index (R) of a WDN has been proposed which is the product of 8 three indices: (i) the number of users temporary without water, (ii) the water level in the tank, and (iii) 9 the water quality. The Resilience Index is expected to help planners and engineers to evaluate the 10 functionality of a WDN which includes: (1) delivering a certain demand of water with an acceptable 11 level of pressure and quality; (2) the restoration process following an extreme event. A small town in the 12 South of Italy has been selected as a case study to show the applicability of this index using different 13 disruptive scenarios and restoration plans. The numerical results show the importance of the partition of 14 the network in districts to reduce the extension of disservices. It is also shown the necessity to consider 15 the indices separately to find trends that cannot be captured by the global index. Advantages and 16 disadvantages of the different restoration plans are discussed. The proposed indices can be implemented 17 in a decision support tool used by governmental agencies which want to include the restoration process, 18 the environmental and social aspects in their design procedure. 20The water distribution networks and the Critical Infrastructures (CI) in general provide services by 24 allowing flows of fuels, materials, information, electric power etc.. The disruptions change the 25 operability state of parts of the network (e.g. nodes and/or links), and then the recovery actions restore 26 the functionality of the damaged parts of the network, allowing the performance of the system to return 27 to the nominal levels as fast as possible. In the past, emphasis was given to the physical protection of 28 water distribution networks, but now attention is shifting toward the infrastructure resilience, defined as 29 the ability of infrastructure systems to withstand, adapt to, and rapidly recover from the effects of a 30 disruptive event. This concept is becoming increasingly important in the context of CIs and defining 31 infrastructure functionality is essential for evaluating its resilience (Cimellaro et al., 2014a). Although 32 several authors (Holling, 1973; Mileti, 1999; Fiksel, 2003) have worked in the field of Disaster 33 Resilience, Bruneau et al. (2003) offered the first broad definition of this quantity including the effects 34 of losses, mitigation and rapid recovery. In their study, they identify four dimensions of community 35 resilience, namely: i) technical, ii) organizational, iii) social, and iv) economic. However, in their work 36 they did not provide a d...

Summary A performance‐based earthquake engineering approach is developed for the seismic risk assessment of fixed‐roof atmospheric steel liquid storage tanks. The proposed method is based on a surrogate single‐mass model that consists of elastic beam‐column elements and nonlinear springs. Appropriate component and system‐level damage states are defined, following the identification of commonly observed modes of failure that may occur during an earthquake. Incremental dynamic analysis and simplified cloud are offered as potential approaches to derive the distribution of response parameters given the seismic intensity. A parametric investigation that engages the aforementioned analysis methods is conducted on 3 tanks of varying geometry, considering both anchored and unanchored support conditions. Special attention is paid to the elephant's foot buckling formation, by offering extensive information on its capacity and demand representation within the seismic risk assessment process. Seismic fragility curves are initially extracted for the component‐level damage states, to compare the effect of each analysis approach on the estimated performance. The subsequent generation of system‐level fragility curves reveals the issue of nonsequential damage states, whereby significant damage may abruptly appear without precursory lighter damage states.

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