Advanced computational approaches to multi-blast scenario analysis: insights into assessing vulnerabilities in multi-span masonry arch bridges

Thousands of masonry arch bridges currently in service in the Italian railway network were built almost 100 years ago. Despite having often been constructed without any specific seismic design, in general these structures exhibited in the past a non-negligible resilience to seismic shocks, even when located in areas with medium/high seismic hazard.Reliable methods are thus required for simplified seismic vulnerability assessment of such a number of structures, in order to ascertain whether more detailed analyses are needed and/or to provide information for a preliminary prioritization of interventions. In this work, the seismic capacity of single and multi-span masonry arch bridges is assessed by non-linear kinematic limit analysis. To this purpose, both “local” and “global” collapse mechanisms are identified - involving piers, abutments, arches and spandrel walls - considering both the longitudinal and the transverse direction of the bridges. For each mechanism, capacity curves are evaluated, in terms of horizontal acceleration versus displacement of a proper control point. Safety checks are hence performed comparing displacement capacity and demand at different performance limits.These criteria provide the parameters needed for the derivation of fragility curves that can be applied for the definition of a large-scale damage scenario after a seismic event and as a support tool for the prioritization of the possible interventions. The so derived fragility curves could be related to the study of a single bridge (with uncertainties on dimensional and mechanical properties) or of a homogeneous typology of bridge (taxonomy). The paper reports some examples of application to both such cases.KeywordsRailway masonry arch bridgesSimplified seismic vulnerability assessmentCollapse mechanismsNon-linear kinematic limit analysisFragility curves

The shallow foundations that often characterizes multi-span masonry arch bridges are highly vulnerable to the soil settlements typically induced by riverbed scouring. Consequently, monitoring of scouring effects is of paramount importance to ensure the safe operation of these river bridges. Within a recent collaboration between Politecnico di Milano and Regione Lombardia, a multi-span masonry arch bridge has been selected to exemplify a quasi-static monitoring strategy capable of detecting the flood-induced scour. The structure, built during the second half of the 19th century, was subjected to numerous strengthening interventions, especially on the pier foundations resting on the riverbed. The installed heterogeneous sensor network consists of tiltmeters (measuring the rotation of the piers at the skewback level), 1 weather station, 1 hydrometer, and 1 echo-sounder. In addition, the detection of debris accumulation is performed with cameras taking pictures of the piers from the upstream side.After a concise description of the structure and the Sesia River, the paper focuses on the adopted measuring system and the results obtained in the first months of continuous monitoring.KeywordsMasonry bridgeScour actionStructural health monitoringStatic monitoringHydraulics

In this work, the seismic capacity of single and multi-span masonry arch bridges was assessed by limit analysis. A preliminary statistical survey was carried out on a stock of about 750 railway bridges in Italy, classified according to characteristics and expected collapse mechanisms under seismic excitation. A comprehensive parametric study was carried out on identified homogeneous classes, to calculate limit horizontal accelerations triggering the collapse mechanism in longitudinal and transverse directions. Iso-acceleration envelope curves, representing limit horizontal acceleration of the bridge as a function of geometric parameters, were then derived. These graphs can be used for preliminary seismic safety checking of existing masonry bridges, once the main geometric parameters are available by simple visual inspections and geometric surveys, and can easily be implemented in a Bridge Management System to prioritise seismic retrofitting interventions.

Three-dimensional modelling of a multi-span masonry arch bridge: Influence of soil compressibility on the structural response under vertical static loads

Advanced computational approaches to multi-blast scenario analysis: insights into assessing vulnerabilities in multi-span masonry arch bridges

The German Unity Traffic Program includes seven projects in the New German Countries with about 2000 km of motorway. Four of these projects are completely new motorways, the other three projects consist of the widening of existing motorways, which were built between 1934 and 1939, and which were left without much alteration and maintenance until the change of government in 1989. In most sections these three motorways have been and will be widened from 24 m to 37 m, combined with a redevelopment of the lines, gradients and junctions. However, often the new location and geometry are not completely different from the old ones, and in these cases the preservation of existing bridges is an option to be considered. The old bridges were deficient in many different areas. Nevertheless, in several cases investigations succeeded in working out solutions with affordable rehabilitation actions. In most cases these were structures of historic engineering value or with a special presence as a landmark. The examples include the reconstruction of large natural stone piers for the use of the two new carriageways and the widening of a multi-span stone masonry arch bridge for the use of one carriageway. Furthermore, the preservation of a large masonry arch overpass by the construction of an underpinning structure is described.

Existing old masonry arch bridges represent an architectural and cultural heritage of inestimable value, assuming nowadays an important strategic role since most of them are still in service and link roads of primary importance for vehicular traffic. They were mostly built in the last century without considering any horizontal action, and nowadays are serving roads characterized by a transit loads certainly heavier and more frequent than the ones of past. Moreover, very often due to absence of maintenance and to weathering conditions, the elements deteriorate more and more with a consequent loss of integrity and reduction of their carrying capacity. In this paper the seismic assessment of an old multi span masonry arch bridge still in service is illustrated. Pushover analyses are performed with the aim to investigate the numerical model sensitivity and the influence on the global nonlinear response of the bridge components.

Introduction: Existing old masonry arch bridges represent an architectural and cultural heritage of inestimable value because most of them were built in the last century and are still in service. They represent a very important part of roads and railways networks, having also an important strategic role. They are actually serving roads characterized by transit loads definitively heavier and more frequent than the ones of the past. Moreover, very often maintenance absence and material worn away, increased by the way by the environmental conditions, accelerate more and more the elements deterioration with a consequent loss of integrity and reduction of their carrying capacity. Methods: In this paper the seismic assessment of an old multi span masonry arch bridge still in service is evaluated. The bridge, located in Southern Italy, was built before the Second World War and crosses the “Cavone” River, from which it takes the name. Results and Conclusion: A series of numerical analyses are performed in order to evaluate its seismic performance and the model sensitivity with respect to the assumed masonry mechanical properties.

This paper describes the dynamic and quasi-static tests performed in a multispan masonry arch bridge, under railway traffic actions. The dynamic forced vibration tests performed under train loading allowed to characterize the dynamic response of the bridge in terms of accelerations in the deck and piers. The quasi-static tests were performed using two in service freight train passages circulating at reduced speed and allowed monitoring particularly deformations in the arch. The main objective of this work is to use these experimental results for validation of the numerical model of Durraes bridge for dynamic and static analysis.

The Olla bridge is a multi-span masonry arch bridge dating back to the second half of the 19th century. The bridge is 117 m long and includes five arches of different spans. Since no original drawings or blueprints of the bridge were found in the archives, the missing information on the geometry of the structure were retrieved through a geomatic survey, whereas the unknown structural details were assumed according to historical handbooks and similar projects. In addition, limited material samples were taken to solve typical uncertainties such as the effective thickness of arches. Subsequently, ambient vibration tests were performed, and different output-only techniques were applied to the acquired time series with the two-fold objective of identifying the dynamic characteristics of the bridge and roughly verifying the invariance of the modal parameters. Finally, all the available information were summarised in a Finite Element model, that – after the updating of uncertain parameters – turned out to be capable of reproducing the identified dynamic characteristics of the structure with a high level of accuracy.

The Olla bridge is a multi-span masonry arch bridge dating back to the second part of the 19th century. The structure, 117 m long, includes five arches of different span and crosses the Stura river close to the small town of Gaiola, about 16 km far from Cuneo (Piedmont, Northern Italy). The central span of the bridge was destroyed during the 2nd World War and rebuilt in 1945. Recently, damages (i.e., the opening of some cracks) have been reported on two arches and the structural assessment of the structure is ongoing.

Mesoscale analysis of multi-span masonry arch bridges

Three-dimensional mesoscale modelling of multi-span masonry arch bridges subjected to scour

Flood-induced forces and collapse mechanism of historical multi-span masonry arch bridges: The Putang bridge case

Modern approaches to multispan masonry bridges are approximate in many ways: load distribution, masonry degradation, fill-to-barrel, span-to-span, and span-to-pier interaction are taken into account by means of approximate models or are neglected. At the end of the assessment procedure, the approximation to the load carrying capacity of the bridge cannot be easily quantified. In Part I of this paper, an extension of the classical approach to masonry arches was formulated taking into account the nonlinear response of masonry, a limit to compressive inelastic strains, and assuming simplifying but conservative assumptions. The procedure allows the analysis of multispan masonry bridges considering the nonlinear response of arches and barrels and the mutual interaction. The response of two- and three-span prototypes is compared to that of a single arch; then the procedure is applied to a six 18.5-m span in-service viaduct. A detailed comparison with the single-span-bridge approach is discussed. Specific attention is paid to the evolution of the collapse mechanism and to the effect of load distribution, addressing the concentrated loads versus distributed equivalent loads problem and showing how the limit to compressive inelastic strains, i.e., to masonry ductility, may be of great importance to the structural analysis of masonry bridges.