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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]

Confinement of reinforced concrete members has repeatedly proven crucial when structures are exposed to strong ground motions. Yet, unconfined concrete is still widely used in developing countries with significant seismic hazard. To quantify the effect of lack of confinement on collapse probability of reinforced concrete frames, incremental dynamic analyses were conducted on two 4-story reinforced concrete moment resisting frame buildings using 5 ground motions. The structures are identical and comply to Eurocode demands except for the fact that one is completely unconfined whereas the other is confined according to the code. The analyses were conducted in OpenSEES using Mander’s material model for confined and unconfined concrete. Based on the results of the analyses, collapse fragility curves were created for each structure. The results show statistically significant effect of confinement on the collapse probability of the reinforced concrete frame. The prabability of collapse is 1.2 and 12 %, respectively, for the code complying and the unconfined structure exposed to a design level earthquake. [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]

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]

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]