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This article presents a numerical study that aims to explore the dynamic behavior of railway bridges under vibrations induced by heavy-haul traffic. For this purpose, a finite element code that can conduct moving load and moving mass analysis of single span bridges was developed. The software was validated by comparing the numerical response to the analytical solution for various speeds. The numerical analysis of the benchmark bridge under the benchmark train showed the interplay between the natural frequency of the bridge, the mass of the train and the loading frequency. A comprehensive parametric study to investigate the impact of different parameters on the dynamic behavior of railway bridges is also provided. The bridge span length, normalized train length, normalized mass of the train, bridge deck stiffness, and train speed are the variables considered in the parametric study. The results of the extensive numerical analyses improve the understanding of railway bridge behavior under heavy-haul trains, and highlight the impact of the inertial effect of the trains on bridges, especially for varying span length and deck stiffness. It is also demonstrated that, when the train-to-bridge mass ratio exceeds 40%, the inertial effects of the train mass needs to be included in the analysis in order to obtain a reliable estimate of the bridge behavior under different train speeds. [ABSTRACT FROM AUTHOR]

This article presents a novel methodology to extract the bridge frequencies from the vibrations recorded on train-mounted sensors. Continuous wavelet transform is used to distinguish the bridge frequencies from the other peaks that are visible in the Fourier amplitude spectrum of the accelerations recorded on train bogies. The efficacy of the proposed method is demonstrated through numerical case studies. For this, a detailed three-dimensional finite element model that can capture the vibration characteristics of the bridge, track, and train is created, and each component of the model is separately validated. The train model used is a three-dimensional multi-degree-of-freedom system that can simulate the pitching and rolling behavior. The train was then virtually driven over the bridge at different speeds and under varying track irregularities to evaluate the robustness of the proposed method in extracting bridge frequencies from train-mounted sensors under different conditions. The proposed methodology is shown to be capable of identifying bridge modal frequencies even for aggressive track irregularity profiles and relatively high speeds of trains. [ABSTRACT FROM AUTHOR]

Damage detection algorithms employing the conventional acceleration measurements and the associated modal features may underperform due to the limited number of sensors used in the monitoring and the smoothing effect of spline functions used to increase the spatial resolution. The effectiveness of such algorithms could be increased if a more accurate estimate of mode shapes were provided. This study presents a hybrid structural health monitoring method for vibration-based damage detection of bridge-type structures. The proposed method is based on the fusion of data from conventional accelerometers and computer vision-based measurements. The most commonly used mode shape-based damage measures, namely, the mode shape curvature method, the modal strain energy method, and the modal flexibility method, are used for damage detection. The accuracy of these parameters used together with the conventional sparse sensor setups and the proposed hybrid approach is investigated in numerical case studies, with damage scenarios simulated on a simply-supported bridge. The simulations involve measuring the acceleration response of the bridge to ambient vibrations and train crossings and then processing the data to determine the modal frequencies and mode shapes. The efficiency and accuracy of the proposed hybrid health monitoring methodology are demonstrated in case studies involving scenarios in which conventional acceleration measurements fail to detect and locate damage. The robustness of the proposed method against various levels of noise is shown as well. In the studies considered, damage as small as 10% decrease in flexural stiffness of the bridge and localized in less than 1% of the span-length of the bridge is reliably detected even with very high levels of measurement noise. Finally, a modified modal flexibility damage parameter is derived and used to alleviate the shortcomings of the modal flexibility damage parameter. [ABSTRACT FROM AUTHOR]

This article proposes a novel method, entitled Reference-based Component Scaling (RCS) method, for estimation of bridge mode shapes using vehicle scanning methods. The proposed method uses two instrumented vehicles to measure the accelerations on the bridge. While one vehicle remains stationary on a pre-determined location, the other one travels over the bridge with a constant speed both exciting the bridge and recording its response. The accelerations recorded on both vehicles are then processed using variational mode decomposition method and Hilbert transform to obtain their modal components. Leveraging its comprehensive framework that incorporates modal components derived from both vehicles, the RCS method effectively tackles the primary challenges encountered by vehicle scanning methods. These challenges include: i) shifting and shrinking effects of bridge damping on mode shapes, ii) distortions in modal components due to incomplete elimination of the roughness effect and iii) distortions in modal components caused by acceleration peaks during the vehicle´s transition from a rigid platform to the bridge. To this end, the RCS method addresses adverse effects of bridge damping without a priori knowledge of the modal damping ratios. To assess the accuracy of the proposed method, numerical analyses were carried out on three different bridges with different number of spans and boundary conditions. The effect of crucial parameters such as road roughness, bridge damping, uncertainties in measurements, and existing traffic on the accuracy of the proposed method was investigated. The results of the numerical study show that the RCS method stands alone in providing accurate estimates of mode shapes of bridges that are seated on elastic bearings, that have realistic damping ratios and relatively high road roughness profiles. • A novel vehicle scanning method to estimate the mode shapes of bridges is proposed. • The Reference-based Component Scaling (RCS) Method uses two instrumented vehicles to measure the response of the bridge. • Through the normalization process, the RCS method tackles the challenges that current drive-by methods cannot address. • The RCS method stands alone in providing accurate estimates of mode shapes of bridges on elastic bearings that have realistic damping ratios. [ABSTRACT FROM AUTHOR]

The recent bridge collapses worldwide underscored the perilous state of the global bridge infrastructure. Structural health monitoring (SHM) methods, particularly vibration-based techniques, offer a non-destructive approach to evaluate bridge conditions. However, installing dedicated SHM systems on each of the millions of bridges worldwide is prohibitively expensive. Vehicle scanning methods (VSM) have emerged as a cost-effective alternative, leveraging vehicle-mounted sensors for bridge assessment. Previous VSM research has primarily focused on frequency and mode shape identification through accelerations derived from numerical models. A smaller subset has explored damage detection, either based on modal properties or direct analysis of vehicle accelerations. This study proposes a new damage index that distinguishes itself by establishing a physical connection between the accelerations recorded on the vehicle and the instantaneous curvature of the bridge. This analytical connection provides a straightforward and effective means for damage detection and localization in bridges using VSM, offering the advantage of efficiency and accuracy. As such, the proposed damage index avoids the use of modal properties for damage detection, which are known to be prone to several factors and are not necessarily accurate enough when used in VSM applications, and the over-fitting problems associated with data driven methods. Numerical investigations indicate that the proposed damage index is robust against the potentially adverse effects of several parameters including road roughness, measurement noise, bridge frequency, damage location, variations in boundary conditions, and vehicle speeds. • Physical connection between contact point accelerations and bridge damage is developed • Based on this connection, we propose a damage index that can detect and locate damage • The proposed damage index was shown to be robust against several parameters • The physical connection paves the way for accurate damage detection and localization. [ABSTRACT FROM AUTHOR]

• Experimental campaign was conducted to evaluate the damping in masonry arch bridges under service loads. • Both ambient vibrations and vibrations under train loads were monitored and the damping values were extracted. • Damping ratios from ambient vibrations were shown to be unfit for use in dynamic analysis of masonry arch bridges under service loads. • Suitability of different viscous damping models in emulating damping behavior of masonry arch bridges was investigated. • The inherent nonlinear mechanisms in discrete-continuum models can be sufficient to capture the energy dissipation in masonry arch bridges under service loads. This article investigates the damping behavior of masonry arch bridges under service loads extracted from experimental data and provides guidelines on how to emulate this behavior in numerical analysis, particularly in discrete element model applications. First, an experimental campaign is undertaken and vibrations on three masonry arch railway bridges under train loads were monitored. The modal damping ratios from several sensors on each bridge were extracted by isolating the modal component of free decay vibrations which commence immediately after the train leaves the bridge. The modal damping ratios identified under service loads were compared with their counterparts identified under ambient vibrations. The suitability of mass-proportional, stiffness-proportional and Rayleigh damping models in emulating damping in masonry arch bridges was evaluated. In the numerical phase of the study, a single-arch masonry bridge was modeled using mixed discrete continuum approach and a moving load analysis was conducted without applying any additional viscous damping. The results of the numerical analysis indicate that the inherent damping in discrete element models provided by their nonlinear nature can be sufficient to emulate the damping behavior of masonry arch bridges under service loads. The research provided in this article is unique in the sense that it combines an experimental study and a numerical study on damping of masonry arch bridges under service loads. Unlike its counterparts in literature, which use either ambient vibrations or seismic action, damping values are computed under appropriate levels of vibration amplitudes for service loads, which is critical to estimate the modal damping ratios accurately under these loads. [ABSTRACT FROM AUTHOR]

This study systematically assesses the efficacy of the vehicle scanning methods (VSM) in accurately estimating the mode shapes of bridges seated on elastic supports. Three state-of-the-art VSM methods are employed to obtain the mode shapes of bridges using the vehicle data during its travel. Two of the evaluated methods use a signal decomposition technique to extract the modal components of the bridge from the contact point of the response while the third one relies on the segmentation of the measured signals along the bridge deck and applying an operational modal analysis tool to each segmented signal to estimate the mode shapes. Numerical analyses are conducted on one single- and one two-span bridge, considering smooth and rough road profiles, different vehicle speeds, and presence of lead vehicle. The accuracy of the numerical models used in developing and assessing vehicle scanning models is tested, and the results of the study demonstrate the method using a half-car vehicle model and signal decomposition technique shows robustness against increasing vehicle speeds and road roughness while the method applying the segmentation of the measured signals provides relatively accurate mode shape estimates at the bridge edges at low speed, although the three methods have their limitations. It is also observed that simplified bridge and vehicle models can hide potential challenges that arise from the complexity of actual vehicle and bridge systems. Considering that a significant number of bridges worldwide are built on elastic supports, the practical success of vehicle scanning methods depends on their ability to handle elastic boundary conditions with reliability. Therefore, the article provides valuable insights into the capabilities and limitations of the current vehicle scanning methods, paving the way for further advancements and refinements in these techniques. [ABSTRACT FROM AUTHOR]

Highlights: [•] The possible influence of degradation on seismic Capacity Design is investigated. [•] Premature corrosion of stirrups can reduce the shear strength of members. [•] The reduction in shear strength can lead to a brittle failure of members. [•] The influence of material properties and environmental conditions is investigated. [•] This paper is a contribution to bridge Material Science and Earthquake Engineering. [Copyright &y& Elsevier]

Sensitivity of earthquake risk models to uncertainties in hazard, exposure and vulnerability components has been investigated. The study is conducted for two test beds with distinctive socio-economic characteristics; Zeytinburnu and Los Angeles. Results are evaluated in terms of overall damage estimates as well as damage estimates of individual building typologies relative to one another. The distribution of damage estimates shows that the respective earthquake risk models are significantly affected by the vulnerability model. Further, the vulnerability model used in the earthquake risk model also influences the ranking of the building typologies according to their damage estimates. In comparison to that, the quality and the level of details of the building exposure database and the selected ground motion prediction equation seem to have less effect on the damage estimates. [ABSTRACT FROM AUTHOR]

In this study, the multihazard response of code-designed conventional and base-isolated steel frame buildings is evaluated using nonlinear response history analysis. The results of hazard and structural response analysis for 3-story moment-resisting frame buildings are presented in this paper. Three-dimensional models for both buildings are created, and seismic response is assessed for three scenario earthquakes. The response history analysis results indicate that the performance of the isolated building is superior to the conventional building in the design event. However, for the Maximum Considered Earthquake, the presence of outliers in the response data reduces confidence that the isolated building provides superior performance to its conventional counterpart. The potential causes of the outliers have been carefully evaluated. [ABSTRACT FROM AUTHOR]

Abstract: The capability of current nonlinear static procedures in capturing torsional effects was evaluated by comparing their estimates to the “exact” results, obtained from nonlinear response history analyses under a ground motion ensemble scaled to 3 different hazard levels. Two different types of eccentricities were considered. In the first case, the mass center of the floor of a symmetric plan structure was shifted in one direction to create a uni-directional eccentricity and in the other case a structure with a plan asymmetry in both horizontal directions was used. Results of numerical analyses show that far-fault and near-fault ground motions have similar influences on the displacement demand of structures as far as torsional effects are concerned. The recent nonlinear static procedures proposed for asymmetric buildings were found to be effective in capturing torsional effects whereas the classical nonlinear static procedure developed originally for planar systems significantly underestimates torsional rotation demands in structures. [Copyright &y& Elsevier]

Abstract: Displacement-based damage functions for the components of reinforced concrete (RC) moment resisting frames have been developed. RC columns, beams and brick infills were considered in this study as the structural elements that contribute to the seismic behavior of RC moment resisting frames. Finite element analyses were carried out on RC columns and beams to investigate effects of their material and geometrical properties on the behavior of these elements, and also to develop the damage functions. The independent parameter used in the damage functions developed for RC columns was the interstorey drift ratio, while rotation was used as the main parameter to evaluate damage in RC beams. The equivalent strut models available in the literature were used to determine the parameters affecting the damageability of brick infills and to develop drift-based damage functions. Additional damage functions for shear critical RC columns and beams were also developed. The damage functions proposed were validated via comparison to the test results available in the literature. These damage functions are proposed to be used for the seismic performance evaluation of RC moment resisting frames. [Copyright &y& Elsevier]

A detailed seismic performance assessment procedure has been developed for reinforced concrete (RC) frame buildings with masonry infill walls. The procedure is based on member damage functions, in terms of interstory drift ratios. These functions are developed for the primary components, namely, columns, beams, and infill walls. For developing these functions, analytical investigations to determine the influence of several parameters on the damageability of components were combined with experimental data. A new approach has been developed to synthesize component damage states to determine the story and eventually the building level performance states. The procedure has been calibrated and compared with other procedures by predicting the observed performance of three buildings exposed to recent earthquakes in Turkey. It is concluded that the developed procedure can satisfactorily predict the damage experienced by most of the components of the studied buildings. Moreover, the procedure reasonably captured the observed building damage states. Accordingly, the developed procedure can be used for a reliable performance assessment as well as performance-based design of RC frame structures. [ABSTRACT FROM AUTHOR]

Research has been undertaken to develop damage curves for reinforced concrete column members. A broad range of parameters that influence the damageability of reinforced concrete columns were investigated using finite element program ANSYS v6.1. Damage curves expressed in terms of interstory drift ratio were developed for three levels of ductility from the results of numerical investigations. The levels of ductility were determined based on the axial load level and the transverse reinforcement ratio. These curves are invaluable for estimating damage level of reinforced concrete frame buildings, which are predominantly used throughout the world, especially in developing countries. In addition, many procedures used to evaluate building performance employ acceptance criteria for the components comprising the whole structure so these curves are also recommended for use in the acceptability of reinforced concrete columns of frame structures. [Copyright &y& Elsevier]

A new framework for long-term monitoring of bridges is proposed in order to negate (i) the impact of measurement uncertainties on damage detection in vibration-based structural health monitoring and (ii) the low sensitivity of damage indicators to low levels of damage. The framework is developed using three vibration-based damage indicators that have an intuitive physical correlation with damage: modal curvature, modal strain energy and modal flexibility. The article first quantifies the efficacy of these damage indicators when based on two observations, one from the undamaged state and one from the monitored state, in detecting and locating damage for different damage levels that are simulated on an 84-m long railway bridge. A long-term monitoring framework based on a new parameter defined as the frequency of the damage indicator exceeding the threshold value within a population of observations is developed. Impact of several factors including the damage location, damage indicator used in the framework, and the noise level on the success of the developed framework was investigated through numerical analysis. The new parameter, when used together with modal strain energy, was shown to provide a very clear picture of damage initiation and development over time starting from very low damage levels. Furthermore, the location of the simulated damage can be identified successfully at all damage levels and even for very high noise levels using the proposed framework. [ABSTRACT FROM AUTHOR]

Seismic behavior of masonry walls has been heavily investigated, especially by means of laboratory experiments employing cyclic tests to determine the mechanical parameters and seismic capacity. Nevertheless, the dynamic properties of the tested walls often remain unknown, even though the nature of the seismic response is dynamic and profoundly affected by the structure's dynamic properties. This paper presents an investigation on the dynamic properties of three different masonry wall panels in healthy and damaged states, and examines if damage quantification via tracking the changes in dynamic properties is feasible. Ambient vibration and impact measurements are used for the dynamic identification of wall panels, before and after they are tested in reversed-cyclic in-plane shear-compression tests. The natural frequencies, damping ratios, and mode shapes of the walls are determined and compared to each other. Moreover, the damage progression and its effect on the dynamic features of the URM wall panel is investigated using a discrete element model of the benchmark wall that is validated in terms of the force-displacement response and damage pattern of the wall. The results of the study indicate that changes in natural frequencies and mode shapes are traceable, although it is difficult to infer damage quantification relationships from these changes. The outcomes of this study also highlight that numerical models verified with the nonlinear quasi-static behavior do not necessarily match the wall's dynamic behavior, and that more research is required to update nonlinear numerical models. Overall, the results contribute to the knowledge regarding the dynamic characteristics of masonry walls in healthy and damaged conditions, and to quantify the damage in masonry walls as well as the changes in their dynamic properties. • Cyclic shear-compression tests on three stone masonry wall panels. • Dynamic identification in healthy state and after damage. • Effects of damages on the dynamic properties of the walls. • Effects of strengthening on the dynamic properties of the walls. • Numerical investigation of modal properties in healthy and damaged states. [ABSTRACT FROM AUTHOR]

• A new framework for OSP is proposed to consider model uncertainties. • Apriori sensitivity analysis to determine modeling parameters. • Probabilistic modal analysis to quantify the uncertainty in modal displacements. • Hierarchical clustering for optimum sensor locations and sensor number. • EFI-based OSP methodologies are also applied to the same structure. The uncertainties in the numerical models used for the optimal sensor placement (OSP) studies of civil infrastructures, specifically bridges, considerably affect the results. These effects can be more prominent if the modeling uncertainties are of a kind that significantly alters the mode shapes of the structure, such as the boundary conditions of the model. Yet, these effects on the results of OSP analysis remain unexplored, and there are no available methodologies to address all types of model uncertainties in OSP for civil infrastructures. This research presents a new framework to determine the optimal sensor locations to identify the modal properties of bridges under severe modeling uncertainties and its application on a railway bridge. The framework includes finite element model generation and a sensitivity study to select the most influential parameters that change the dynamic response of the bridge. The selected parameters are used in Monte Carlo simulations, and the results enable quantifying the relative amount of information presented at the candidate sensor locations. This information is combined with the spatial position of the candidate sensor locations, and a hierarchical clustering algorithm is used to obtain the optimal sensor locations and the number of sensors. In addition, the OSP analysis is carried out using the Effective Independence method to contribute to the state-of-the-art literature that investigates the uncertainties in OSP for civil infrastructures and uses this method. [ABSTRACT FROM AUTHOR]

• A novel idea to generate prediction models is proposed. • Failure type and force capacity estimated by Lasso regression. • Evaluation of out-of-plane bending behavior of masonry wallettes. • Non-spatial and spatial stochastic analysis of the brickwork assemblages. • Quantification of the variability in the masonry response. The out-of-plane flexural bending capacity of masonry is a fundamental property for understanding the behavior of masonry structures. This study investigates the behavior of unreinforced masonry wallettes subjected to combined compression-flexural loading using the discrete element method (DEM), and provides a novel framework to estimate the masonry strength. A simplified micro-modeling strategy is utilized to analyze a masonry wallette, including the variation of the mechanical properties in masonry units and joints. Stochastic DEM analyses are performed to simulate brickwork assemblages, assuming a strong unit-weak joint material model typical of most masonry buildings, including historical ones. Once the proposed computational approach is validated against the experimental findings, the effect of spatial and non-spatial variation of mechanical properties is explored. Two failure types are identified: joint failure and brick failure. For each failure mechanism, the variability of the response and the effects of the modeling parameters on the load-carrying capacity is quantified. Afterward, Lasso regression is employed to determine predictive equations in terms of the material properties and vertical pressure on the wallette. The results show that the most important parameters changing the response are the joint tensile strength and the amount of vertical stress for joint failure , whereas the unit tensile strength dominates the response for brick failure. Overall, this research proposes a novel framework adopting validated advanced computational models that feed on simple test results to generate data that is further utilized for training response prediction models for complex structures. [ABSTRACT FROM AUTHOR]