1,721,006 research outputs found
Stationary proposal importance sampling for structural reliability of aging RC bridges
No full textSafety assessment of aging bridges may require the modeling of complex deterioration processes, further exacerbating in time the uncertainties involved in the mechanical response of critical members. Simulation-based techniques applied to life-cycle reliability problems may rely on time-consuming structural analyses, leading to untenable computational efforts and impairing the accuracy of the numerical estimates. This paper discusses an efficient computational framework for time-variant failure probability based on Importance Sampling (IS) with Stationary Proposal (SP) distribution. This novel methodology exploits numerical approaches traditionally developed for time-invariant structural reliability problems and extends them into a life-cycle context. Specifically, the simulation density is adaptively selected by minimizing the Kullback-Leibler Cross-Entropy from a chosen family of parametric distributions. The numerical procedure is applied to lifetime structural reliability of a reinforced concrete bridge exposed to chloride-induced corrosion
Seismic risk of aging bridge networks by Cross-entropy-based Stationary Proposal Importance Sampling
No full textThe feasibility of traditional Monte Carlo simulation techniques in structural reliability analysis and lifeline risk assessment can be limited in practice when intensive numerical analyses are required to estimate small failure probabilities over complex limit state domains. Life-cycle assessment of deteriorating systems may also involve the modeling of complex stochastic processes, further exacerbating the computational effort. This paper presents a novel mathematical framework based on Importance Sampling (IS) to estimate timevariant seismic risk metrics of aging infrastructure systems. The simulation procedure allows adaptively selecting a near-optimal Stationary Proposal (SP) sampling density from a chosen family of parametric distributions by minimizing the Kullback–Leibler (KL) Cross-Entropy (CE). Potentialities and limitations of the proposed numerical approach is investigated in comparison with traditional simulation approaches to address the multi-hazard risk of a deteriorating bridge network exposed to regional seismic hazard
Probabilistic life-cycle seismic resilience assessment of aging bridge networks considering infrastructure upgrading
No full textThis paper presents a probabilistic framework for life-cycle seismic resilience assessment of aging bridges and transportation road networks subjected to infrastructure upgrade. The proposed framework accounts for the uncertainties in damage occurrence of vulnerable deteriorating bridges and restoration rapidity of the overall system functionality. The time-variant bridge fragilities and the damage combinations probability are evaluated considering different earthquake magnitudes and epicenter locations that define the seismic scenario. Traffic analyses are carried out to assess in probabilistic terms the network functionality profiles, the corresponding resilience levels, and a damage-based measure of life-cycle resilience. The effects of structural deterioration, seismic damage, and post-event repair actions under uncertainty are related to traffic restrictions applied over the network. The framework is applied to reinforced concrete bridges exposed to chloride-induced corrosion and simple road networks with a single bridge or two bridges in series under different earthquake scenarios. The effect of network upgrading is also investigated by adding road segments with a vulnerable bridge to strengthen the network connectivity and improve the lifetime system resilience. The results show the capability of the proposed resilience framework in quantifying the detrimental effects of structural deterioration at the network scale and the beneficial consequences of infrastructure investments, such as enhancing the network redundancy with the construction of an additional highway branch
Role of the earthquake scenario on life-cycle seismic resilience of aging bridge networks
Full text linkThe time-variant structural capacity of critical infrastructure facilities is an important performance indicator in the definition of reliable policies for emergency management and long-term planning of risk mitigation strategies. This paper investigates the seismic resilience of transportation road networks based on a probabilistic framework for life-cycle seismic assessment of deteriorating bridges under prescribed earthquake scenarios with different magnitude and epicenter location. The seismic damage suffered by the exposed bridges and the effects of repair actions are related to traffic limitations and vehicle restrictions implemented over the network. The life-cycle seismic resilience is evaluated under post-event structural recovery of each bridge processes and functionality restoration of the network traffic capacity. The proposed framework is applied to reinforced concrete bridges exposed to seismic hazard and chloride-induced corrosion in a highway network with detour and re-entry link. The results emphasize the role of network topology, earthquake scenario, and time-variant structural deterioration of spatially distributed bridges on the life-cycle functionality and seismic resilience of aging road networks
Seismic resilience of deteriorating RC bridges and road networks under climate change
No full textThis paper investigates the life-cycle seismic resilience of aging road networks with reinforced concrete (RC) bridges under the effects of climate change. The physical damage suffered by the exposed bridges is related to traffic limitations implemented over the network. A probabilistic framework is proposed to aggregate the time-variant seismic capacity assessment of RC structures exposed to chloride-induced corrosion with the traffic response of the transportation network. The life-cycle seismic resilience of a simple road network is evaluated based on the restoration of the network functionality guaranteed by the post-event recovery of the damaged bridge. The results highlight the detrimental effects of the progressive increase in the deterioration rate induced by climate change, impairing the seismic capacity of single bridges and, in turn, the seismic resilience of the overall transportation system
Sensitivity analysis of bridge structural vulnerability class based on Italian Guidelines
No full textOptimal management of existing bridges over their service life is critical for infrastructure owners and practitioners who are called to guarantee adequate structural and functional performance of the transportation network they administrate. Documental analysis and visual inspections are valuable data supporting the decision-making process. A valuable support in the Italian context is provided by the “Guidelines for risk classification and management, safety assessment and monitoring of existing bridges” introduced in 2020. The guidelines promote a multi-hazard approach based on Attention Classes (ACs) defined from the combination of risk indicators regarding operating conditions from different perspectives, such as structural, seismic, hydraulic, and geological. This paper is aimed at providing a sensitivity analysis regarding the Structural Vulnerability Class (VC) defined by the Guidelines, with the aim of investigating the impact of epistemic uncertainties inherently biasing the bridge assessment, such as expert judgement subjectivity and missing historical data and asbuilt documentation
Structural modelling and probabilistic seismic assessment of existing long-span precast industrial buildings
No full textPrecast concrete frame structures constitute a major construction technology of the industrial built heritage within the Italian territory. Most of these buildings were conceived according to obsolete seismic design criteria with lower hazard than currently recognised standards, whilst the most industrialised areas spread over the Italian territory were declared seismically active since less than 20 years. This paper focuses on seismic performance assessment of long-span flat-roof industrial buildings, representative of modern design technologies. Buildings located in areas with increasing seismic hazard over the Italian territory were designed following an archetype existing building based on standards in force after 1996. Seismic performance is investigated by modal response analysis, non-linear static pushover analysis, and non-linear time-history analysis with a multi-stripe approach. The flexibility of the horizontal diaphragm and the interaction of the resisting frame with the cladding system are addressed by exploring progressively advanced modelling strategies up to a detailed assembly comprising roof members, peripheral panels, and all related connections. Mechanical non-linearities regarding column elements, dowel beam-to-column and slab-to-beam connections, strap tie-back and bracket bearing panel-to-frame connections are modelled with lumped plasticity employing experimentally calibrated constitutive laws. Seismic risk is assessed by estimating via multi-stripe analysis failure rates encompassing performance levels from usability preventing damage to global collapse. The results are site-dependent, and the need for retrofit of these typical precast systems is deemed to be urgent for both buildings designed in areas of average and high seismicity
Probabilistic life-cycle resilience assessment of aging bridges and road networks under seismic and environmental hazards
No full textThis paper presents a probabilistic framework for life-cycle resilience assessment of aging bridges and transportation road networks under seismic and environmental hazards. The time-variant fragilities and damage probabilities of the deteriorating bridges in the network are evaluated by considering the role of the seismic scenario in terms of earthquake magnitude and epicentral distance. The effects of structural deterioration, seismic damage, and post-event repair actions under uncertainty are related to traffic restrictions applied over the network. Traffic analysis is hence carried out to assess in probabilistic terms the network functionality profiles, the corresponding resilience levels, and a damage-based measure of life-cycle resilience. The proposed framework is applied to reinforced concrete bridges exposed to chloride-induced corrosion and simple road networks with a single bridge or two bridges in series under different earthquake scenarios
Numerical assessment of seismic retrofit interventions on a long-span precast industrial building
No full textLifetime seismic resilience of aging bridges and road networks
No full textThe performance of lifelines under damage and emergency conditions induced by sudden extreme events, such as earthquakes, can be assessed based on the concept of resilience. Damage also arises in time due to aging, affecting the structural performance of each network component and, consequently, impairing the overall system functionality. Furthermore, the sparse location over the network of vulnerable deteriorating structures, such as spatially distributed bridges, should be taken into account to establish proper infrastructure management policies. In this article, a probabilistic approach is proposed to assess the seismic performance of transportation networks considering the uncertainties involved in the lifetime structural response of aging bridges under different earthquake scenarios. The time-variant seismic capacity associated with prescribed limit states is evaluated by nonlinear incremental dynamic analysis. The initial damage induced by seismic events and its recovery process through structural repair is related to traffic restrictions to different road users. Traffic flow distribution analyses are carried out over the road network to assess the post-event system functionality and the corresponding seismic resilience. The role of different factors such as aging, earthquake scenario, and seismic capacity correlation is investigated by considering spatially distributed reinforced concrete bridges exposed to corrosion and highway networks with detours and re-entry links
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