1,721,222 research outputs found
On the applicability of transfer function models for ssi embedment effects
Full text linkSoil-structure interaction (SSI) effects are typically neglected for relatively lightweight buildings that are less than two-three storeys high with a limited footprint area and resting on shallow foundations (i.e., not featuring a basement). However, when the above conditions are not satisfied, and in particular when large basements are present, important kinematic SSI may develop, causing the foundation-level motion to deviate from the free-field one due to embedment effects. In the literature, transfer function models that estimate the filtering effect induced by rigid massless embedded foundations are available to “transform” foundation-level recordings into free-field ones, and vice-versa. This work describes therefore a numerical study aimed at assessing potential limits of the applicability of such transfer functions through the employment of a 3D nonlinear soil-block model representing a layered soil, recently developed and validated by the authors, and featuring on top a large heavy building with basement. A number of finite element site response analyses were carried out for different seismic input signals, soil profiles and embedment depths of the building’s basement. The numerically obtained transfer functions were compared with the curves derived using two analytical models. It was observed that the latter are able to reliably predict the embedment effects in “idealised” soil/input conditions under which they have been developed. However, in real conditions, namely when a non-homogeneous profile with nonlinear behaviour under a given seismic excitation is considered, especially in presence of a basement that is more than one storey high, they may fail in capturing some features, such as the frequency-dependent amplification of the motion at the basement level of a building with respect to the free-field one
Ultrasound-Assisted Synthesis of Cross-Linked Poly(ethylene glycol) Nanostructures with Hydrophobic Core and Hydrophilic Shell
No full textAffidabilità sismica dei sistemi di distribuzione dell’acqua potabile in ambito urbano: metodologia di calcolo ed applicazione
No full textVariations between foundation-level recordings and free-field earthquake ground motions: numerical study at soft-soil sites
No full textIt is typically assumed that accelerograms obtained from ground motion recording instruments adequately installed inside a building can be considered as representative of free-field conditions if the structure is less than 2-3 storeys high and does not feature a basement or a massive foundation system. In this work, such an assumption is verified through nonlinear soil-block finite element analyses, considering the induced seismicity Groningen gas field as a case-study and both types of structures. The capability of the numerical model in adequately reproducing nonlinear soil response and capturing interaction between soil and structure is first verified through a number of analyses and cross-checks. Considering soil profiles at the locations of different recording stations in the Groningen field, together with accelerograms from recent events in the region, the results obtained with the numerical model confirm that recordings from instruments located at the base of lightweight structures are not affected by Soil-Structure Interaction (SSI) effects, neither kinematic nor inertial. Heavy structures with a basement, however, do exhibit recordings with variations with respect to the free-field; these are identified and possible corrections to the recordings are analysed. Another set of analyses then demonstrates that soil consolidation prior to the construction of lightweight structures resting on shallow foundations may instead lead to foundation-level recordings that feature high-frequency ground motion amplitudes slightly lower than their free-field counterparts. Additional simplified analyses show the dependency of the recordings on inertial SSI effects due to deformability of the ground supporting the structure
Verso una fruizione inclusive ed indipendente dell’architettura: l’uso di modelli in scala e della realtà aumentata
No full textRelationship between physical impairment, psychological variables and pain in rheumatoid disability. An analysis of their relative impact
No full textSeismic vulnerability assessment of steel storage pallet racks
No full textSteel storage pallet racks are structures composed of cold-formed members designed to store goods. Despite worldwide usage, their dynamic behaviour is still not well known. The goal of this research is to propose a methodology for the seismic vulnerability assessment of steel racks, in terms of fragility curves. The latter are retrieved by means of Multiple-Stripe Analysis, in which the Generalized Conditional Intensity Measure approach is employed for record selection. Two typical rack configurations, unbraced and braced, are analysed, and epistemic uncertainty related to construction details is accounted for by considering different hysteretic connection behaviours and upright moment resistances. Nonlinear dynamic analyses are performed in the down-aisle direction, considering both geometric and material nonlinearities. The obtained results are related to different engineering demand parameters and limit states. The derived fragility functions, if combined with relevant hazard curves, would allow carrying out a seismic risk assessment and mitigation of steel storage racks
Seismic risk of infrastructure systems with treatment of and sensitivity to epistemic uncertainty
Full text linkModern society’s very existence is tied to the proper and reliable functioning of its Critical Infrastructure (CI) systems. In the seismic risk assessment of an infrastructure, taking into account all the relevant uncertainties affecting the problem is crucial. While both aleatory and epistemic uncertainties affect the estimate of seismic risk to an infrastructure and should be considered, the focus herein is on the latter. After providing an up-to-date literature review about the treatment of and sensitivity to epistemic uncertainty, this paper presents a comprehensive framework for seismic risk assessment of interdependent spatially distributed infrastructure systems that accounts for both aleatory and epistemic uncertainties and provides confidence in the estimate, as well as sensitivity of uncertainty in the output to the components of epistemic uncertainty in the input. The logic tree approach is used for the treatment of epistemic uncertainty and for the sensitivity analysis, whose results are presented through tornado diagrams. Sensitivity is also evaluated by elaborating the logic tree results through weighted ANOVA. The formulation is general and can be applied to risk assessment problems involving not only infrastructural but also structural systems. The presented methodology was implemented into an open-source software, OOFIMS, and applied to a synthetic city composed of buildings and a gas network and subjected to seismic hazard. The gas system’s performance is assessed through a flow-based analysis. The seismic hazard, the vulnerability assessment and the evaluation of the gas system’s operational state are addressed with a simulation-based approach. The presence of two systems (buildings and gas network) proves the capability to handle system interdependencies and highlights that uncertainty in models/parameters related to one system can affect uncertainty in the output related to dependent systems
- …
