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Semplified seismic Vulnerability Assessment of Masonry Arch Bridges
Full text linkThis study concerns seismic vulnerability assessment of masonry arch bridges with common typologies in Europe. Bridges are, in most cases, the most vulnerable elements in the transportation network during an earthquake; therefore, their seismic vulnerability assessment is necessary for a proper planning of the emergency phase and to define a priority for retrofit interventions. Masonry arch bridges were subdivided into homogeneous classes of single span and multi-span structures, according to the result of a statistical analysis made up of a large stock of 757 railway bridges located in high seismic areas.
All the different collapse mechanisms for seismic action were studied for each class of masonry arch bridges with application of limit analysis and the calibration with FEM. In particular, limit analysis methods for the seismic assessment of single and multi spans bridges were developed. A innovative limit analysis approach was proposed for the assessment of the global transverse seismic capacity of multi-span masonry bridges with slender piers. Envelope curves representing the seismic capacity expressed in terms of limit horizontal acceleration were derived by parametrical analysis by means of simplified limit analysis. These curves can be used for a simplified vulnerability assessment of masonry arch bridges and for a simple calibration of the judgment obtained by BMS through inspection visits to bridges. In the second part of the study, a new simplified approach for the fast calculation of seismic fragility curves of numerous masonry arch bridge clusters is proposed. The aim of this thesis is to propose a quickly procedure to estimate the seismic vulnerability of extended roadway and railway bridge networks in emergency conditions and to optimize the retrofit interventions
A simplified modelling strategy for FRCM-strengthened masonry panels subjected to the in-plane loading
Full text linkThis paper applies the discrete macro-element method (DMEM) to validate a simplified modelling strategy for the nonlinear in-plane response of masonry panels strengthened by Fabric Reinforced Cementitious Matrix (FRCM) systems. Following the general DMEM strategy, the presence of continuous strengthening fibre-reinforced composite layers applied on the external faces of the masonry wall has been described using 1D nonlinear links simulating the tensile failure of the reinforcement and its shear-delamination from the masonry substrate. Specifically, the masonry element and the FRCM layers have been simulated considering an equivalent homogeneous continuum material, discretised using a regular mesh of elastic-shear-deformable discrete elements interacting along their rigid edges through nonlinear discrete interfaces. The numerical analyses were conducted using the OpenSees software platform by simulating the experimental diagonal compression tests available in the literature. The results of the analyses are presented in terms of stress–strain curves, failure mechanisms and stress contours. The comparisons with the experimental observations have evidenced the capability of the adopted simplified modelling strategy to accurately predict the nonlinear and ultimate behaviour of masonry panels strengthened by FRMC systems with a potential limited computational burden
Influence of damage on the seismic failure analysis of masonry arches
No full textMasonry arches are typical structural elements of existing masonry constructions. Many existing masonry buildings and bridges in Europe, and indeed in many other parts of the world, are quite old and consequently may show defects and/or degradation. Such defects and degradations in masonry constructions may be caused by different factors, both environmental and human. One of the most common defects that develop over time in masonry structures involves local or uniform reduction in the thickness of the structural elements. This paper uses limit analysis to examine the influence of local thickness reductions on the seismic capacity of masonry arches: in terms of collapse acceleration and changes in collapse mechanism
Derivation of analytical seismic fragility functions for common masonry bridge types: methodology and application to real cases
No full textBridges are, in most cases, the most vulnerable elements in the transportation network during an earthquake; therefore, their seismic vulnerability assessment is necessary for a proper planning of the emergency phase and to define a priority for retrofit interventions. A new simplified approach for the fast evaluation of seismic fragility curves of numerous masonry arch bridge clusters is proposed. The aim of this paper is to propose a quickly procedure to estimate the seismic vulnerability of extended roadway and railway bridge networks in emergency conditions and to optimize the retrofit interventions. This methodology can be applied at regional level for the vulnerability assessment of transportation networks with regard to the specific scenario earthquakes formulated. It would allow us to better manage the phase after the main shock so that it should be possible to rationalise resources for the assessment of bridges, to temporarily close the most vulnerable segments of railway or road network and to maintain the use of the safest ones
Structural assessment outcomes from the demolition of an arch bridge with cluster modal analysis
Full text linkAn old arch bridge was subject to demolition due to life-cycle damage and environmental issues, in a central-east region of Italy. During the demolition process, several dynamic tests were executed in order to evaluate the structural behavior before and during demolition. The classical Modal Analysis methods revealed difficulty in determining the modal parameters, so these results were validated with a newly developed technique of modal parameter identification and then verified with sophisticated finite element models. The structure revealed some surprising results relatively to the dynamic
characteristics before and after the partial demolition
Simplified seismic assessment of multi-span masonry arch bridges
No full textThe paper describes a simplified methodology for the evaluation of the seismic retrofit intervention types to be performed on clusters of multi-span masonry arch bridges, on the basis of the main bridges geometrical characteristics. The structural behaviour of the analysed sample bridges has been evaluated in their principal directions highlighting the potential local and global vulnerabilities and the related retrofit intervention typologies that need to be selected. The main aim of this study is to take the form of an useful tool for identify the best retrofit strategies for each masonry bridge structure in function of its geometrical characteristics and thus planning rationally the management of bridges belonging to rail and road networks
Contribution of in situ and laboratory investigations for assessing seismic vulnerability of existing bridges
No full textThis work describes the main results of an in situ experimental campaign carried out in the context of the seismic assessment of 71 existing road bridges as representative of the main structural typologies located in the Veneto region and pertaining to the regional roadway managing authority Veneto Strade SpA. An initial in situ and laboratory experimental campaign on basic materials and an overall geometrical survey were carried out for each bridge, using different tests according to the construction typologies, with the aim of characterising the main mechanical parameters of the significant structural elements. Structural assessment has been subsequently carried out according to the parameters derived from the above campaign and the design ground motion action. The results have been compared with those deriving from a preliminary analysis conducted on the basis of some assumptions on materials’ mechanical characteristics related to the original design documents and the construction practice at the time of the structures’ edification. This comparative analysis could give some insights on appropriate and rational planning of inspections on existing bridges and reliability of basic assumptions for their seismic assessment
Seimic assessment and retrofit of masonry arch bridges
No full textThe existing stock of road and railway masonry arch bridges in Italy and in most European countries frequently exhibits insufficient performance, both in terms of structural safety and
functionality. Many of these structures are located on major traffic lines, in high seismicity areas, and most of them need to be improved in terms of their carrying capacity and to be upgraded to the standards of the current seismic codes. Quick and reliable procedures are then needed to assess the capacity of these structures and methodological approaches are required for the retrofitting interventions.
In this work, a simplified procedure for the seismic assessment of masonry arch bridges is proposed. The ultimate capacity of homogeneous classes of single span and multi-span bridges is evaluated in terms of limit peak ground acceleration curves. The subsequent choice of retrofitting interventions is therefore discussed by presenting some reference examples. It is shown how the seismic enhancement of the structural behaviour is often coupled with a strengthening intervention of the resisting system for vertical loads, and with the functional renovation of the bridge
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