The increased occurrence and intensity of flooding events have represented a real threat to bridge reliability and end-user safety. As flood vulnerability assessment is a valuable tool for enhancing ...the resilience of bridges to climate change, it is of interest to push the development of such methods. To this end, a computationally efficient methodology to assess the flood vulnerability of a bridge was developed and implemented in a case study. A particular focus was devoted to modelling wood debris loads on the bridge pier, for which two different approaches were implemented. The first is a standards-based approach, whereas the second is based on up-to-date research data. The results indicate that the second approach is less conservative as it leads up to a 40% higher exceedance probability for the considered limit states. The interaction between wood debris loads and local scour was also examined and proved to have a relevant impact on the vulnerability of the bridge. These results highlight the shortcomings of the existing standards in providing accurate results. It is perceived that not only will the new quantitative tool be valuable in ensuring optimal bridge design, but it will also be beneficial for assessing bridge risk mitigation measures.
In this study, a vulnerability analysis of road and railway embankments to earthquake-induced liquefaction deformations was carried out. The result of the vulnerability analysis was a set of ...fragility curves that were obtained for several embankment and soil-profile geometries, as well as for the material properties of the liquefiable layer. The fragility curves were based on the numerical calculations obtained from FLAC 2D software in conjunction with the PM4Sand material model used for simulating the behavior of liquefaction-susceptible soils during dynamic shaking. The fragility analysis was performed using an incremental dynamic analysis approach considering a set of 30 ground motions and at least eight intensity levels. Permanent vertical displacement of the middle top point of the embankment was selected as the damage parameter, while the intensity measure was expressed in terms of peak ground acceleration at bedrock. Fragility curves were derived for three damage states, including minor, moderate and extensive damage, based on threshold values proposed in the literature. The influence of a single model variable was examined through comparison of the fragility curves.
From a lifecycle perspective, assessing bridge vulnerability is a key element of implementing effective risk mitigation and management strategies. This study offers an integrated and computationally ...efficient approach to evaluate bridges' vulnerability to failure due to hydrodynamic and wood debris forces and the concurrent action of local scour. The vulnerability analysis follows a stochastic approach and is developed through a case‐study analysis of a bridge that has a high proneness to flood‐related hazards. The modelling of the wood debris accumulation is accomplished based both on a Standard approach and on findings drawn from up‐to‐date research data. It is found that the shape of wood debris accumulation envisioned in the first approach has a particularly adverse effect on the bridge's vulnerability, exposing its limitations. A detailed and comprehensive methodology for assessing the risk related to flood hazards on bridges is also presented. It is perceived that not only will this new tool be valuable in estimating the flood loss assessment on bridges, but it will also be beneficial for facilitating decision‐making processes and in finding effective countermeasures for risk mitigation of flood‐related hazards.
An approach for estimation of scenario-based liquefaction probability with consideration of ground-motion randomness is introduced. It is based on a modified version of the cyclic stress liquefaction ...assessment procedure where the cyclic stress and cyclic resistance ratios are considered time dependent and ground-motion dependent. This makes it possible to estimate the probability of liquefaction for a given seismic scenario. The approach can be applied to a given site to screen out the issue of liquefaction if the estimated probability of liquefaction is lower or equal to a tolerable value. The proposed decision-making is demonstrated for two sites with liquefaction-susceptible soils.
The seismic behaviour of a building on a liquefiable deposit is a complex interaction which involves quantifying both shaking induced damage and permanent ground deformation-related damage. In this ...paper the key parameters that influence both surface shaking and foundation settlements have been identified as the depth, thickness and liquefaction resistance of an equivalent liquefiable layer. These parameters can be used to develop an ‘equivalent soil profile’ that is analogous to the equivalent single degree-of-freedom that reduces the complexity of the dynamic response of a building into comparable and easily understood quantities. The equivalent soil profile is quantified independent of the seismic hazard, making it compatible with performance based design and assessment frameworks such that the building and soil profile can be directly assessed at different levels of seismic hazard. Several numerical studies are presented that demonstrate the influence of these key parameters on the ground surface shaking and foundation settlement. A set of criteria are proposed for classifying soil profiles into 22 different soil classes for regional loss assessment. An algorithm was developed for automatically fitting the equivalent soil profile to a cone penetration test trace and issues with the fitting are discussed. Field reconnaissance was undertaken to collect additional data to support existing datasets on the performance of buildings in Adapazari, during the 1999 Kocaeli, Turkey, earthquake (Mw = 7.4). The field case history data was used to investigate the correlation between the depth, thickness and liquefaction resistance of an equivalent liquefiable layer, on the extent of foundation permanent deformation. The case history data showed that in general a shallow, thick and weak liquefiable layer near the surface results in significant settlement but a lack of data for buildings on non-liquefiable deposits and the additional complexities involved with real buildings and soil deposits, meant that the trends observed in the idealised numerical models could not identified in the field case history data set.
Modal parameter evaluation is widely used for structural health monitoring, damage detection, and numerical model calibration. This study benchmarks two methods for modal identification under ...controlled laboratory conditions using operational modal analysis to compare dynamic parameters from ambient vibrations and shaker tests. A 2‐storey 3D spatial steel frame equipped with 3‐axial accelerometers is used as a case study. The identified dynamic parameters are benchmarked against a preliminary finite element model by computing Auto‐MAC and MAC matrices. It can be concluded that the preliminary FEM approach performs better in the prediction of modes shapes than natural frequencies. It was found that analysing the structural response to both ambient and artificially induced excitations provide a more complete understanding of a structure's dynamic characteristics. An additional mode shape was identified from the artificially induced excitation that was not previously captured from the ambient excitation.
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