1,720,979 research outputs found
Strategies for Seismic Assessment of Common Existing Reinforced Concrete Bridges Typologies
No full textThis study concerns a new probabilistic framework to evaluate road/railway bridges after an earthquake by means of analytical fragility curves and inspections on the structure. In particular, the assessment is performed on existing reinforced concrete (RC) bridges with a common structural scheme in Italy (multi-span simply supported girder bridges). The framework is set up of 6 steps and each step is investigated. Steps 1 and 2 are a sort of preliminary work before the seismic event occurs: the creation of a database to collect all information about bridges in specific road/railway networks (step 1) and the generation of fragility curves for each bridge (step 2): fragility curves are instruments describing the probability of a structure being damaged beyond a specific damage state for various levels of ground shaking. Since step 2 is a crucial step for the outcomes of the framework, a wide investigation on the generation of fragility curves is presented, considering bridges located in strategic road network points in Veneto region (North-Eastern Italy) and different numerical modellings, in order to evaluate the best seismic vulnerability assessment. Moreover, particular attention is given to retrofit interventions by means of Fiber Reinforced Polymer (FRP) and their effect on bridge seismic vulnerability reduction. The other steps concern activities to carry out after a seismic event, useful for emergency and post-emergency phases. Step 3 regards a method to decide if inspections on bridge are needed in relation to the occurred earthquake seismic intensity; if the seismic intensity measure reaches a specific threshold, step 4 suggests how to perform visual inspections on bridges, under a probabilistic point of view, and to generate the damaged bridge fragility curves. After that, the last two steps try to give useful information to Institution and owners of bridges in order to reach an optimal road/railway network management in post-earthquake phases. Step 5 concerns a quick procedure to decide whether or not allowing traffic over damaged bridges, whereas step 6 gives information about economical benefits coming from a comparison between replace costs and retrofitting costs (considering FRP retrofitting interventions) of damaged bridges. In order to clarify the framework procedure, an example for each step is developed
A parametric study on the fragility of typical existing concrete bridges in seismic areas
No full textSeismic vulnerability of bridges in transport networks subjected to environmental deterioration
Full text linkThis paper investigates the problem of management, maintenance and planning of interventions in transport networks located in seismic zones, in relation to the actual state of degradation of their most vulnerable elements, as bridges. The study consists in two phases: the first phase is concerned with definition of the seismic vulnerability of a typical bridge in the network, through the construction of fragility curves calculated taking into account the corrosion of the reinforcing steel as the main cause of environmental deterioration. Once the fragility curves of the deteriorated bridges are computed, the second phase consists in the analysis of the vulnerability of the transport network in which the bridges are included taking into account the modification of the traffic flows when bridge infrastructures are damaged. The results of this pilot study can be used as a first step for a proper allocation of economic resources in the planning of seismic retrofit interventions to minimize the overall risk and manage the immediate post-earthquake emergency phase and guide rescuers in reaching the affected and critical areas
Riduzione della vulnerabilità sismica di ponti stradali esistenti tramite confinamento con compositi FRP
No full textInfluenza dell’inclinazione in pianta dell’impalcato sulla vulnerabilità sismica di ponti stradali con tipologia ricorrente
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A probabilistic strategy for seismic assessment and FRP retrofitting of existing bridges
No full textThis study proposes a holistic probabilistic framework to evaluate existing road and railway bridges after an earthquake by means of analytical fragility curves and visual inspections. Although visual inspections are affected by uncertainties, they are usually considered in a deterministic way, while in this work they are taken into account in a probabilistic point manner. Moreover, extra focus is given on retrofitting interventions by means of Fiber Reinforced Polymer materials and their costs. A probabilistic methodology is formed to evaluate possible standardized interventions on existing bridges after a seismic event. The proposed
framework, consists of six basic steps and it is applied on a reinforced concrete bridge case study, which is a common structural typology in Italian roadway infrastructural networks. The main aim is to provide useful information to public authorities in order to decide whether or not they should allowtraffic over the bridge andwhether to repair immediately earthquake damaged bridges. The outcomes of this framework can be used to improve procedures used for the seismic assessment of the whole road and railway networks to better plan emergency, post-emergency actions and define a general priority for an optimal budget allocation
Effect of FRP retrofit interventions on seismic vulnerability of existing bridges
No full textBridges are the one of the most vulnerable elements in existing road and railway networks dur- ing earthquakes, hence the assessment of their seismic vulnerability and the study of the techniques to reduce it are common issues in the general context of the management of the transportation network. One of the most diffused method to evaluate seismic vulnerability of existing bridges is based on the calculation of the fragility curves, which give the probability of a bridge reaching a certain damage state for a given ground motion pa- rameter. By means of fragility curves, damage of critical elements of the bridge can be predicted and conse- quent economic losses can be estimated. Moreover retrofit interventions can be planned.
In this framework fragility curves for a bridge having a common structural scheme in Italy (multi-span simply supported reinforced concrete bridge) have been calculated by means of non-linear dynamic analyses. Then the influence of methods to reduce seismic vulnerability of the bridge by pier confinement with fiber- reinforced polymers (FRP) was studied. Theoretical models for the evaluation of the constitutive law of con- fined piers were developed to generate the fragility curves of the bridge taking retrofit effects into account
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