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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]

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]

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. DOI: 10.1061/(ASCE)ST.1943-541X.0000260 CE Database subject headings: Bridges; Seismic effects; Deterioration; Corrosion; Probability; Aging. Author keywords: Bridges; Seismic; Deterioration; Corrosion; Probability; Fragility.

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]

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]