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Recognising the criticality of highway bridges for the socio-economic development of a nation, multiple researchers have endeavoured towards quantifying the seismic fragility of these key infrastructure elements. Given the present boom in urbanisation, however, there may also be an appreciable likelihood of vehicle presence on the highway bridge deck during an earthquake event. This study focuses on the impact assessment of vehicle-bridge-interaction (VBI) on the seismic fragility of highway bridges by explicitly accounting for vehicular movement atop the bridge deck during seismic shaking. Addressing existing drawbacks in literature that typically adopts a simplified modelling strategy and static vehicle placement, this paper considers different types of moving vehicles (modelled as mass-spring-dashpot system analogies) for VBI assessment through a novel algorithm. The proposed framework also accounts for uncertainties involved in the moving vehicle analysis, pertaining to vehicle characteristics and driver's perception of the earthquake. The framework is demonstrated on representative multi-span continuous steel girder bridges located in Central and Southeastern United States. A comparative assessment of hysteretic response of bridge components and seismic fragility curves indicate a considerable influence of vehicular movement on bridge damage, signifying the importance of considering moving VBI effects for thorough seismic assessment of highway bridge structures. [ABSTRACT FROM AUTHOR]

Corrosion of reinforced concrete (RC) structures constitutes a critical form of environmental deterioration and may significantly increase the vulnerability of old non‐seismically designed buildings during earthquake events. This study proposes a probabilistic framework to evaluate the influence of corrosion deterioration on the lifetime seismic fragility of low‐ductility RC frame buildings. In contrast to limited past literature on this topic, the proposed framework offers novel contributions. This is one of the first study to consider potential alteration in failure modes of building components (from flexure to flexure‐shear) due to the time‐dependent aging process. Numerical models validated with past experimental test results are utilized to capture these failure modes, which are particularly relevant for low ductility RC frames designed prior to the introduction of modern seismic codes. Secondly, given the gamut of uncertainties associated with the corrosion process, this study develops condition‐dependent seismic fragility functions independent from an assumed exposure scenario, as often done in literature. These functions can be easily adopted by design engineers and stakeholders for prompt fragility assessment, and subsequent decision‐making without the need for computationally expensive finite element (FE) model runs. The proposed framework is demonstrated on a benchmark three‐story RC frame that considers time‐varying seismic demand models and damage state thresholds while accounting for the uncertain corrosion deterioration process and ground motion record‐to‐record variability. [ABSTRACT FROM AUTHOR]

This study offers a probabilistic framework for the seismic life-cycle cost (SLCC) assessment of aging highway bridge structures in complex seismogenic zones, followed by a case-study application on a popular bridge class in Seattle (United States). The proposed framework efficiently handles the implications of differing seismic hazard scenarios (crustal and subduction earthquakes) along with time-dependent bridge deterioration mechanisms on seismic fragility and lifetime economic losses. These losses, stemming from the seismic damage-induced repair of critical bridge components, may be uncertain depending on the repair technique, availability of resources, or decision of the stakeholder. Unlike previous works that have evaluated seismic losses under a single hazard source and deterministic repair costs, this study aimed for a better approximation of the accumulated lifetime losses for aging highway bridges under simultaneous exposure to differing hazard sources, while accounting for repair uncertainties. The case-study results revealed that the SLCCs using deaggregated hazard sources incurred significantly higher contributions from subduction earthquake sources than shallow crustal earthquake sources for both as-built and aging bridge structures. Lastly, based on the proposed framework, a statistical model is proposed for easy adoptability by stakeholders and decision-makers for the SLCC computation of bridge structures in the case-study region. [ABSTRACT FROM AUTHOR]

Despite the potential of long duration earthquakes in subduction zones, little attention has been paid on seismic vulnerability assessment of highway bridges that are simultaneously undergoing prolonged corrosion deterioration. Consequently, this study presents a framework for considering the joint impact of ground motion duration and chloride-induced corrosion deterioration on the lifetime seismic vulnerability of aging highway bridge structures. The proposed framework is then applied to a representative case-study multi-span simply supported highway bridge located in subduction earthquake zone within Seattle, U.S.A. A detailed three-dimensional analytical models are first developed that account for the nonlinear behaviour of different bridge components, including experimentally validated column model capable of capturing cyclic degradation of force–deformation response. Suites of spectrally equivalent short and long duration ground motions are adopted followed by an incremental dynamic analysis-based framework for seismic fragility assessment. Deterministic seismic response assessment reveals a higher seismic demand on multiple bridge components under long duration ground motion record as compared to spectrally equivalent short duration record. Lastly, the bridge components and system fragility curves are developed considering modelling and deterioration uncertainties. Results reveal the significant vulnerability of bridge components and system under the joint impact of long duration earthquake shock and corrosion deterioration. [ABSTRACT FROM AUTHOR]

Multi-span simply supported (MSSS) highway bridges are one of the most common bridge types across the world and have several vulnerable components, including bearings, piers, and abutments. Although several past studies have evaluated the seismic response and fragility of common multi-span simply supported bridges, there is negligible research that explores the influence of bearing types, and non-ductile failure modes of bridge piers on the performance of older non-seismically designed simply supported bridges. Additionally, a better understanding of seismic risk to highway transportation systems necessitates the exploration of design code advances and subsequent impact on the seismic vulnerability of MSSS highway bridges. Consequently, this study also focuses on developing and comparing fragility curves for the older design era non-seismically designed, and modern era seismically designed MSSS bridges. High-fidelity three-dimensional (3-D) analytical models, which account for the nonlinear behavior of different components, including non-ductile failure modes of bridge piers, are developed. Deterministic seismic response assessment reveals a higher seismic demand on bridge pier for MSSS bridges with steel bearings as compared to those with elastomeric bearings. The bridge component and system fragility curves are developed with a suite of ground motions representative of the seismic hazard of the case-study region. Results reveal the significant vulnerability of older non-seismically designed MSSS bridge with steel bearings due to the non-ductile failure of the bridge pier. The vulnerability of the bridge is significantly reduced with the adoption of modern seismic design and detailing practices. [ABSTRACT FROM AUTHOR]

Bridges are frequently subjected to permit loads. While deciding on permitting such loads, bridge owners usually adopt a tiered approach for structural analysis, assessment, and measurement. Under these complexities of decision-making, the owner can decide to adopt structural health monitoring (SHM) strategies in guiding the issuance of permits. A value of information (VoI) framework can be utilised by the owner to estimate the benefit of various SHM strategies. This study proposes a novel VoI framework which incorporates tiered assessments common in engineering practice. The proposed decision framework utilizes a generic approach to incorporate the successive tiers of measurement, analysis, and assessment. A real-world inspired case study of a reinforced concrete bridge pier crosshead subjected to high shear is used to demonstrate the proposed framework. Using a novel and practical tiered-assessment and multi-intervention option strategy, the potential monetary benefit of strain-based SHM strategies is quantified. It is found that the potential benefit of SHM is particularly high when high risks are involved. SHM is also found to be highly beneficial when slight changes in structural assessment could trigger different intervention actions by the stakeholder. The study also identifies the significant role that low-cost low-accuracy SHM strategies can play in decision guidance by providing adequate information for decision-making at a cheaper cost. [ABSTRACT FROM AUTHOR]

Significant research efforts have been recently invested towards the evaluation of chloride-induced deterioration effects on the seismic vulnerability of aging highway bridges. Furthermore, when located in coastal cities with increased urbanisation or near shipyards, bridge structures may also be subjected to potentially high levels of carbon dioxide emissions. Consequently, the physicochemical process resulting from simultaneous ingress of chlorides and concrete carbonation may lead to accelerated corrosion deterioration of reinforced concrete components, as evidenced in past experimental tests. Nevertheless, little attention has been paid towards modelling this joint influence of chloride and carbonation-induced corrosion deterioration on strength degradation of bridge components. The present study proposes a numerical iterative scheme to evaluate the simultaneous impact of these deterioration mechanisms on the seismic response and bridge fragility. The proposed framework is demonstrated on a case-study multi-span continuous steel girder bridge in Central and Southeastern United States. Results reveal a considerable influence on the corrosion initiation time and seismic vulnerability under the concurrent carbonation and chloride ingress. Furthermore, this study also conducts a systematic exploration of uncertainty at different stages of the deterioration process. This exercise helps provide recommendations on balancing between computational complexity and accuracy of seismic fragility predictions. [ABSTRACT FROM AUTHOR]

Recent findings reported in the contemporary literature have underlined the criticality of including climate change effects in models of deterioration of civil engineering structures. Highway bridges, when exposed to unfavorable environmental conditions and climate change settings and when simultaneously situated in moderately to highly active seismic zones, may experience reduced structural performance during earthquake events. For bridges in such regions, past studies have revealed the criticality of considering deterioration when computing seismic losses, which may constitute a significant percentage of the life-cycle cost planning for the structure. In acknowledging the potential effects of climate change on bridge deterioration and seismic fragility, a renewed systematic assessment of seismic life-cycle cost then becomes necessary for informed decision making and economic investment. Addressing this critical need, we propose a novel framework for evaluating the lifetime seismic losses of highway bridges that considers earthquake hazards, aging effects, and global warming due to climate change. The proposed framework was first demonstrated on two structurally distinct case-study bridges––multispan continuous (MSC) steel and MSC concrete-girder bridges located in the southeastern United States. Both bridge types comprise multiple seismically vulnerable bridge components that are also prone to the adverse effects of environmental degradation. It was found that there was a substantial underprediction in the lifetime seismic loss––by 6.7% for the MSC steel bridge and 13.2% for the MSC concrete bridge––when expected future climate change was neglected. Additionally, the proposed framework was applied to a seismically designed MSC concrete-girder bridge in order to evaluate the influence of seismic design practices on the lifetime seismic losses of aging highway bridges, including climate change effects. [ABSTRACT FROM AUTHOR]

This study investigates the seismic life-cycle cost of aging highway bridges under chloride exposure when subjected to multiple main shock earthquake events along the design lifetime of the structure. While chloride induced corrosion manifests as a continuous deterioration process, earthquake occurrences are typically intermittent. Although relatively weak seismic events that induce none-to-minor bridge damage may not instigate immediate intervention and repair, resulting structural cracks may further accelerate the corrosion process. This study presents a novel Monte Carlo based methodology that explicitly considers potentially altered deterioration pattern between seismic shocks as well as uncertainty in earthquake occurrences, record-to-record variability, repair decisions and repair processes for seismic life-cycle cost computations. The proposed framework also eliminates the need for the often improbable assumption in past literature on seismic life-cycle cost assessment that necessitates structural rehabilitation to pre-hazard states regardless of the seismic damage level. Case-study application of the proposed framework is demonstrated on a single column integral bridge located in the marine splash zone in California, United States. Results from multiple main shock analysis of both non-deteriorating and aging case-study bridge reveals a significant contribution of cumulative damage from corrosion deterioration and shock sequences towards seismic loss and life-cycle cost assessment. [ABSTRACT FROM AUTHOR]

Passive control systems, such as buckling‐restrained braces (BRBs), have emerged as efficient tools for seismic response control of new and existing structures by imparting strength and stiffness to buildings, while providing additional high and stable energy dissipation capacity. Systems equipped with BRBs have been widely investigated in literature; however, only a deterministic description of the BRBs' properties is typically considered. These properties are provided by the manufacturer and are successively validated by qualification control tests according to code‐based tolerance limits. Therefore, the device properties introduced within the structure could differ from their nominal design estimates, potentially leading to an undesired seismic performance. This study proposes a probabilistic assessment framework to evaluate the influence of BRBs' uncertainty on the seismic response of a retrofitted RC frame. For the case study, a benchmark three‐story RC moment‐resisting frame is considered where BRBs' uncertainty is defined compatible to the standardized tolerance limits of devices' quality control tests. This uncertainty is implemented through a two‐level factorial design strategy and Latin hypercube sampling technique. Cloud analysis and probabilistic seismic demand models are used to develop fragility functions for the bare and retrofitted frame for four damage states while also accounting for the uncertainty in the property of BRBs. Risk estimates are successively evaluated for three case study regions. The results show that, for the considered case study structure, these uncertainties could lead to an increase of fragility up to 21% and a variation in seismic risk estimates up to 56%. [ABSTRACT FROM AUTHOR]

Despite the potential of high-consequence events, rarity of earthquake occurrences in moderate seismic zones and a misconstrued perception of risk has often led to a delayed onset of seismic detailing practices for highway bridges. While substantial literature exists on the development of seismic fragility curves for nonseismically designed highway bridges in these regions, additional efforts are required for vulnerability assessment of bridges with improved seismic detailing. Risk evaluation and preparedness of the transportation infrastructure to withstand damaging earthquakes requires seismic fragility estimation of bridges from both preseismic and postseismic design eras. Unlike past literature advocating traditional fragility curves for seismic vulnerability assessment, this study proposes parameterized fragility functions that offer multiple unique advantages. While incorporating the key aspects of seismic design detailing, these functions are conditioned on ground motion intensity as well as field measurable bridge-specific structural parameters. As a test bed, this study chooses the moderate seismic zone of central and southeastern US to develop parameterized fragility models for four prevalent seismically designed bridge classes using modern gradient-based least-square boosting algorithms. A statistical screening procedure helps prune a wide array of bridge parameters to the most critical ones that affect seismic response and fragility. Predicted fragility estimates using surrogate models show satisfactory match with benchmark Monte Carlo simulations rendering confidence in vulnerability predictions. Lastly, fragility comparisons between bridges with seismic and nonseismic detailing highlight the benefits of modern seismic design practices. The proposed fragility models are aimed to equip asset managers with tools for prompt fragility estimation and decision making. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive open probabilistic seismic risk model for India. The proposed model comprises a nationwide residential and non-residential building exposure model, a selection of analytical seismic vulnerability functions tailored for Indian building classes, and the open implementation of an existing probabilistic seismic hazard model for India. The vulnerability of the building exposure is combined with the seismic hazard using the stochastic (Monte Carlo) event-based calculator of the OpenQuake engine to estimate probabilistic seismic risk metrics such as average annual economic losses and the exceedance probability curves at the national, state, district, and subdistrict levels. The risk model and the underlying datasets, along with the risk metrics calculated at different scales, are intended to be used as tools to quantitatively assess the earthquake risk across India and also compare with other countries to develop risk-informed building design guidelines, for more careful land-use planning, to optimize earthquake insurance pricing, and to enhance general earthquake risk awareness and preparedness. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive open probabilistic seismic risk model for India. The proposed model comprises a nationwide residential and non-residential building exposure model, a selection of analytical seismic vulnerability functions tailored for Indian building classes, and the open implementation of an existing probabilistic seismic hazard model for India. The vulnerability of the building exposure is combined with the seismic hazard using the stochastic (Monte Carlo) event-based calculator of the OpenQuake engine to estimate probabilistic seismic risk metrics such as average annual economic losses and the exceedance probability curves at the national, state, district, and subdistrict levels. The risk model and the underlying datasets, along with the risk metrics calculated at different scales, are intended to be used as tools to quantitatively assess the earthquake risk across India and also compare with other countries to develop risk-informed building design guidelines, for more careful land-use planning, to optimize earthquake insurance pricing, and to enhance general earthquake risk awareness and preparedness. [ABSTRACT FROM AUTHOR]

Civil infrastructure systems when located in high seismic zones may experience multiple earthquake events along their service life. Highway bridges that comprise critical elements of the transportation network are often exposed to harsh environments that exacerbate the structural performance to withstand such repeated shocks. While earthquake occurrences are intermittent in nature, environmental degradation mechanisms such as corrosion deterioration continually weakens the structural capacity. Presently there exists a gap in literature that simultaneously considers such temporally varying multi-hazard threats within a probabilistic framework. This study presents a novel methodology that considers repeated main shock sequences and corrosion deterioration for an index-based estimation of cumulative damage along the service life while considering the associated uncertainties with the earthquake occurrence and the deterioration process. A newly introduced analytical strategy in this study enables the updating of bridge pier section properties reflecting deterioration of an already damaged bridge between subsequent earthquake shock events. The proposed framework is demonstrated on a representative case-study multi-span continuous concrete box-girder bridge in California, United States. The results reveal a significant impact of corrosion deterioration on the seismic damage accumulation under multiple earthquakes and underlines the necessity to incorporate aging effects within bridge asset management in high seismic zones. [ABSTRACT FROM AUTHOR]

Chloride-induced corrosion of highway bridges constitutes a critical form of environmental deterioration and may result in significant escalation of seismic life-cycle costs due to increased fragility during earthquake events. Most of existing literature tends to adopt simplistic uniform area loss assumptions in lieu of potentially complex, yet realistic and more detrimental, pitting corrosion models for seismic vulnerability analysis. Since the degree of deterioration depends on the severity and duration of exposure, there exists a need to investigate the influence of uniform vs. pitting corrosion assumption on seismic lifecycle costs for varied chloride exposure conditions. A case-study example of a highway bridge in Central and Southeastern US reveals consideration of pitting corrosion as critical for extreme exposures compared to relatively minor settings. Subsequently this study provides recommendations to aid bridge engineers and stakeholders to balance between computational cost and accuracy of results to aid prompt decisions on rehabilitation of ageing bridges in different exposure conditions. A framework is also included to compute seismic life-cycle costs from generic measures of corrosion, independent of assumed exposure scenario. This framework is particularly helpful for seismic loss assessment of highway bridges in chloride exposure zones with periodic field measurements to estimate the extent of structural deterioration. [ABSTRACT FROM AUTHOR]

Civil infrastructures, such as highway bridges, located in seismically active regions are often subjected to multiple earthquakes, including multiple main shocks during their service life or main shock–aftershock sequences. Repeated seismic events result in reduced structural capacity and may lead to bridge collapse, causing disruption in the normal functioning of transportation networks. This study proposes a framework to predict damage accumulation in structures subjected to multiple shock scenarios after developing damage index prediction models and accounting for the probabilistic nature of the hazard. The versatility of the proposed framework is demonstrated on a case-study highway bridge located in California for two distinct hazard scenarios: (1) multiple main shocks during the service life and (2) multiple aftershock earthquake occurrences following a single main shock. Results reveal that in both cases there is a significant increase in damage index exceedance probabilities due to repeated shocks within the time window of interest. [ABSTRACT FROM AUTHOR]

The bridge reliability in networks (BRAN) methodology introduced in the companion paper is applied to evaluate the reliability of part of the highway bridge network in South Carolina under a selected seismic scenario. The case study demonstrates Bayesian updating of deterioration parameters across bridges after spatial interpolation of data acquired from limited instrumented bridges. The updated deterioration parameters inform aging bridge seismic fragility curves through multi-dimensional integration of parameterized fragility models, which are utilized to derive bridge failure probabilities. The paper establishes the correlation structure among bridge failures from three information sources to generate realizations of bridge failures for network-level reliability assessments by Monte Carlo analysis. Positive correlations improve the reliability of the case study network, as predicted from network topology. The benefits of the BRAN methodology are highlighted in its applicability to large networks, while addressing some of the existing gaps in bridge network reliability and prioritization studies. [ABSTRACT FROM AUTHOR]

The state-of-the-practice in seismic network reliability assessment of highway bridges often ignores bridge failure correlations imposed by factors such as the network topology, construction methods, and present-day condition of bridges, among others. Additionally, aging bridge seismic fragilities are typically determined simply using historical estimates of deterioration parameters. This research presents a methodology to estimate bridge fragilities using spatially interpolated and updated deterioration parameters from a limited set of instrumented bridges in the network, while incorporating the impacts of overlooked correlation factors in bridge fragility estimates. Simulated samples of correlated bridge failures are used in an enhanced Monte Carlo method to assess bridge network reliability, and the impact of different correlation structures on the network reliability is discussed. The presented methodology aims to provide more realistic estimates of seismic reliability of aging transportation networks and to potentially help network stakeholders to more accurately identify critical bridges for maintenance and retrofit prioritization. [ABSTRACT FROM AUTHOR]

The deteriorating state of highway bridges is traditionally ignored in estimating the seismic reliability of transportation networks. In this study, the present day seismic reliability of ageing bridges in highway networks is evaluated through a time-dependent seismic fragility analysis of typical bridge classes. An efficient algorithm based on finite-state Markov Chain Monte Carlo simulations is also presented to assess the reliability of large ageing highway bridge networks without the need to simplify the network topology. The criticality of ageing bridges is then assessed through different proposed ranking strategies to arrive at an optimised seismic retrofit prioritisation. A case study on an existing bridge network with 515 bridges in the state of South Carolina, USA reveals striking differences between results of the proposed ranking strategies and those from state-of-the-practice methods. Such differences emphasise the significance of accounting for network-level importance in seismic retrofit programs of ageing transportation networks. [ABSTRACT FROM AUTHOR]

This study investigates the sensitivity of seismic fragility estimates for bridge components to variation in structural and liquefiable soil modelling parameters. A rigorous sensitivity analysis is conducted to evaluate the relative importance of 13 random variables that reflect uncertainty in the seismic performance assessment of bridges in regions with liquefiable soils. The results indicate that the fixed and expansion bearings and bent piles tend to be sensitive to the greatest number of modelling parameters for the case study system, while the abutments are less sensitive. The most significant modelling parameters affecting the seismic fragility include such parameters as undrained shear strength of soil, structural damping ratio, soil shear modulus, gap between deck and abutment, ultimate capacity of soil and fixed and expansion bearing coefficients of friction. The 5% and 95% confidence intervals reveal wide bounds on the seismic fragility curves, particularly for more vulnerable bridge components such as the piles or expansion bearings. The results offer insights to improve seismic reliability assessment in liquefaction susceptible regions and provide a basis for efficient bridge network reliability analyses. The findings guide future uncertainty treatment, management of computational resources and investment in refined modelling parameter estimates through field testing or other means. [ABSTRACT FROM AUTHOR]

Deteriorating highway bridges in the United States and worldwide have demonstrated susceptibility to damage in earthquake events, with considerable economic consequences due to repair or replacement. Current seismic loss assessment approaches for these critical elements of the transportation network neglect the effects of aging and degradation on the loss estimate. However, the continued aging and deterioration of bridge infrastructure could not only increase susceptibility to seismic damage, but also have a significant impact on these economic losses. Furthermore, the contribution of individual aging components to system-level losses, correlations between these components, and uncertainty modeling in the risk assessment and repair modeling are all crucial considerations to enhance the accuracy and confidence in bridge loss estimates. In this paper, a new methodology for seismic loss assessment of aging bridges is introduced based on the non-homogeneous Poisson process. Statistical moments of seismic losses can be efficiently estimated, such as the expected value and variance. The approach is unique in its account for time-varying seismic vulnerability, uncertainty in component repair, and the contribution of multiple correlated aging components. A representative case study is presented with two fundamentally distinct highway bridges to demonstrate the effects of corrosion deterioration of different bridge components on the seismic losses. Using the proposed model, a sensitivity study is also conducted to assess the effect of parameter variations on the expected seismic losses. The results reveal that the seismic losses estimated by explicitly considering the effects of deterioration of bridge components is significantly higher than that found by assuming time-invariant structural reliability. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents the formulation of a time-dependent seismic fragility format for bridges, as well as new insights into the potential effects of aging and deterioration on seismic vulnerability traditionally neglected in fragility modeling, including joint impacts of multiple component deterioration not investigated to date. The study evaluates the impact of lifetime exposure to chlorides from deicing salts on the seismic performance of multispan continuous highway bridges, considering corrosion of reinforced concrete columns and steel bridge bearings. The components' degradation and their influence on seismic response are illustrated through three-dimensional nonlinear dynamic analysis. A full probabilistic analysis accounting for variation in bridge, ground motion, and corrosion parameters is conducted to develop time-dependent seismic fragility curves. These fragility curves indicate the evolving potential for component and system damage under seismic loading considering time-dependent corrosion-induced deterioration. The results indicate that while corrosion may actually decrease the seismic vulnerability of some components, most critical components suffer an increase in vulnerability. Quadratic models depicting the change in lognormal seismic fragility parameters are proposed to capture the time-dependent effect of aging on the fragility of the bridge system. Overall, the seismic vulnerability significantly increases throughout the lifetime of the representative bridge geometry, with a 32% shift in the median value of complete damage fragility near the end of the bridge's life. [ABSTRACT FROM AUTHOR]