1,355,733 research outputs found
Individuare le priorità manutentive dei ponti stradali lombardi
No full textIl crollo del Ponte Morandi nell’agosto 2018, e gli eventi che si sono succeduti, hanno portato all’attenzione di tutti la rilevanza della conservazione e della manutenzione delle infrastrutture, dopo un lungo periodo in cui c’era stata una forte concentrazione principalmente sulle attività di costruzione. Questi eventi hanno reso evidente che non è sufficiente progettare e costruire strutture e sistemi infrastrutturali in modo efficiente e funzionale ma, affinché possano continuare a creare valore nel tempo, devono essere adeguatamente conservate, svolgendo attività di ispezione, monitoraggio e manutenzione, che ne assicurino la sicurezza e affidabilità durante tutto il ciclo di vita (Biondini e Frangopol, 2016, 2019). Queste attività richiedono tempi e costi significativi, che crescono ulteriormente nel caso di infrastrutture distribuite sul territorio e gestite da amministrazioni diverse, quali per esempio province e comuni. Per affrontare questa complessità, è necessario programmare le attività di manutenzione, definendo alcune priorità di intervento in modo coerente con le specificità delle diverse infrastrutture. È questo il tema affrontato dal progetto nel quale il Politecnico di Milano è attualmente impegnato con Regione Lombardia, finalizzato alla redazione di linee guida per la classificazione, descrizione, monitoraggio e analisi previsionale del ciclo di vita dei ponti della rete viaria regionale. Si tratta di un’attività ampia e ambiziosa che prevede lo sviluppo di una metodologia per l’individuazione delle priorità di intervento, tenendo conto dei fattori di rischio e del depotenziamento funzionale o interruzione della rete per manutenzione o inagibilità delle singole opere, e di un sistema di supporto alle decisioni per la gestione di ponti e infrastrutture viarie
Probabilistic resilience assessment of aging bridge networks based on damage disaggregation and stationary proposal importance sampling
No full textThis paper presents a mathematical framework to investigate the relative importance of seismic damage scenarios to the probability of failing to meet target performance measures for spatially-distributed aging bridge networks. The proposed framework relies on a statistical approach adapted from disaggregation procedures typical of probabilistic seismic hazard analysis. The estimate accuracy is enhanced using a novel simulation-based methodology proposed in previous works based on Importance Sampling with Stationary Proposal distributions (SP-IS). The basic random variables involved in risk assessment are efficiently sampled from a near-optimal simulation density based on the minimization of the Kullback–Leibler cross-entropy. A simple road network is investigated to highlight the benefits to computational effort of the proposed SP-IS numerical method and to explore the potentialities of the concept of damage disaggregation in communicating to infrastructure managers and policy makers the large-scale consequences of natural hazards and aid the optimal management and prioritization of essential maintenance interventions
Life-Cycle Performance of Deteriorating Structures
No full textThis chapter is aimed at presenting a review of the main principles, concepts, methods, and strategies for life-cycle design and assessment of deteriorating structural systems under uncertainty. General criteria for deterioration modeling are first presented, with emphasis on the effects of corrosion and fatigue in steel structures and chloride-induced corrosion in concrete structures. The timevariant structural performance is then investigated with reference to a set of probabilistic performance indicators, and the structural lifetime assessment and design criteria associated with a reliability target are finally formulated
Survey on Life-Cycle Performance of Civil Structures and Infrastructure Systems
No full textThe Special Project approved by the SEI Technical Activities Division (TAD) Executive Committee for the development of this state-of-the-art report included a survey and an International Workshop on Life-Cycle Performance of Civil Structure and Infrastructure Systems, which was held by invitation only at the ASCE headquarters in Reston, Virginia, on November 10, 2015. The survey was disseminated to selected researchers and experts from universities, industries, engineering firms, and agencies active in the field of life-cycle civil engineering. A brief overview of the main results of the survey are presented in this appendix with emphasis on life-cycle concepts and methods, deterioration and damage evaluation, life-cycle performance indicators, inspection and maintenance procedures, life-cycle cost analysis, and implementation in design practice
Experimental validation of nonlinear finite element analysis of PC bridge deck beams based on the results of full-scale load tests
No full textFull-scale load tests on prestressed concrete (PC) deck beams extracted from a dismantled bridge have been performed within the ongoing BRIDGE|50 research project. The results of this experimental activity, along with the outcomes of non-destructive tests and laboratory tests for mechanical characterization of materials, are considered in this paper for the validation of computational structural analysis models based on PC beam finite elements
with distributed nonlinearity and plane-stress finite elements formulated in accordance with the Modified Compression Field Theory. The accuracy of numerical versus experimental results is evaluated under four-point bending for different shear span ratios and by taking into account the contribution of the top concrete slab on the structural response of the tested beams
Finite Strip Modeling for Optimal Design of Concrete Structures
No full textThe optimal limit state design of prestressed thin-walled folded plate structures under multiple loading conditions is presented. The design variables include (a) geometrical quantities, like the thickness and the dimensions of the structural members, (b) topological parameters, which define the location and the connectivity of such elements, and(c) the characteristics of the eventual prestressing system, described by the prestressing forces and the cables profile. Besides the physical and technological limits on such variables, the design constraints account for given limit states on both the stress and the displacement states which define the structural behavior. The objective of the design process is to find the structural layout which minimizes the structural volume and/or the total prestressing force according to the mentioned side and behavioral constraints. The solution of the corresponding non-linear optimization problem is achieved by using a numerical procedure based on the complex method. The structural analyses required during the optimization process are performed by using the finite strip method. Some applications to the optimal design of beams, vaults and box-girder bridges show the effectiveness of the proposed procedure
Damage modeling and nonlinear analysis of concrete bridges under corrosion
No full textA general approach to nonlinear analysis of concrete bridges under corrosion is presented. This approach is based on the formulation of a three-dimensional reinforced concrete beam finite element which accounts for both mechanical and geometrical nonlinearity. The formulation considers uniform and localized (pitting) corrosion and damage modeling includes the reduction of cross-sectional area of corroded bars, the reduction of ductility of reinforcing steel, the deterioration of concrete strength, and the spalling of concrete cover. The beam finite element is validated with reference to the results of experimental tests carried out on beams with corroded reinforcement. The three-dimensional structural analysis of a reinforced concrete arch bridge under different damage scenarios shows the effectiveness and application potentialities of the proposed formulation for life-cycle assessment and design of concrete bridges exposed to corrosion
Life-cycle and sustainability of structures and infrastructures: ReLUIS collaborative research project
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