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Highway bridges are critical components of the lifeline transport infrastructure in urban areas. They are designed with the expectation of not sustaining significant structural/non‐structural damage after major earthquake‐induced ground shaking. However, in the current structural performance‐based assessment practice, the effects of a pre‐damaged state during ground‐motion sequences are often neglected. Additionally, environmentally induced deterioration mechanisms (e.g., steel rebar corrosion) may exacerbate the consequences of such ground‐motion sequences on the seismic structural performance during the bridge design lifetime; yet such effects are commonly overlooked. This study proposes a computational methodology to derive state‐dependent fragility and vulnerability relationships (i.e., explicitly depending on the damage state achieved by the bridge structure during a first shock) for bridge structures subjected to chloride‐induced corrosion deterioration and ground‐motion sequences. The methodology is demonstrated for a case‐study ordinary bridge structure (representing a typical bridge vulnerability class in southern California) under seismic sequences assembled from the CyberShake 15.12 (hybrid) simulated ground‐motion database. In the proposed approach, parameterised (i.e., dependent on the corrosion deterioration level) vector‐valued probabilistic seismic demand models are developed for the bridge components (i.e., columns and shear keys). These models, calibrated through sequential cloud‐based nonlinear time‐history analyses, relate the dissipated hysteretic energy in the ground‐motion sequence to a deformation‐based engineering demand parameter induced by the first shock and a ground‐motion intensity measure of the second shock for a given corrosion deterioration level. Fragility relationships are first derived for a single ground motion at the component‐level; state‐dependent fragility relationships are then derived by considering the additional damage induced by a second ground motion within the simulated sequence (structure‐specific damage states are considered). Furthermore, a component‐based simulation approach accounting for the correlations across the components' response is utilised to derive fragility relationships at the system level (i.e., for the bridge structure). Finally, appropriate damage‐to‐loss models for ordinary bridges are used to derive state‐dependent vulnerability relationships. The results demonstrate the significant impact of earthquake‐induced ground‐motion sequences and environmentally‐induced corrosion deterioration, emphasising the necessity of accounting for this multi‐hazard threat in the structural performance‐based assessment of bridges. Relative variations up to 120% can be found in the system‐level state‐dependent fragility median values comparing the results for the bridge in pristine and deteriorated conditions. [ABSTRACT FROM AUTHOR]

This paper presents the formulation of a comprehensive risk-targeted performance-based seismic design (PBSD) framework involving the seismic design of bridge piers for California Ordinary Standard Bridges (OSBs), facilitating risk-informed design and decision making in the face of uncertainty. A full-fledged implementation of this all-inclusive design method formulated by retaining the inherent rigor of the underlying seismic performance assessment methodology might impose a seemingly prohibitive computational cost for the available resources in the current scenario of seismic bridge design practice. For reasons of practicability, the findings of the full-fledged design framework are inventively utilized to distill out a simplified and computationally more economical PBSD procedure. Its efficacy is validated using four already-built California testbed OSBs as cases in point. The proposed simplified design methodology is able to (1) find a design point in the primary design parameter space of a bridge to be designed for multiple risk-targeted performance objectives; and (2) delineate an approximate, yet sufficiently accurate, feasible design domain and identify the limit states controlling its boundary in the primary design parameter space of the bridge, at a computational cost significantly lower than that of the original method. [ABSTRACT FROM AUTHOR]

Recent researches are directed towards the regional seismic risk assessment of structures based on a bridge inventory analysis. The framework for traditional regional risk assessments consists of grouping the bridge classes and generating fragility relationships for each bridge class. However, identifying the bridge attributes that dictate the statistically different performances of bridges is often challenging. These attributes also vary depending on the demand parameter under consideration. This paper suggests a multi-parameter fragility methodology using artificial neural network to generate bridge-specific fragility curves without grouping the bridge classes. The proposed methodology helps identify the relative importance of each uncertain parameter on the fragility curves. Results from the case study of skewed box-girder bridges reveal that the ground motion intensity measure, span length, and column longitudinal reinforcement ratio have a significant influence on the seismic fragility of this bridge class. [ABSTRACT FROM AUTHOR]

This study aims to realistically simulate the seismic responses of typical highway bridges in California with considerations of soil-structure interaction effects. The p-y modeling approaches are developed and validated for embankments and pile foundations of bridges. The p-y approach models the lateral and vertical foundation flexibility with distributed p-y springs and associated t-z and q-z springs. Building upon the existing p-y models for pile foundations, the study develops the nonlinear p-y springs for embankments based on nonlinear 2D and 3D continuum finite element analysis under passive loading condition along both longitudinal and transverse directions. Closed-form expressions are developed for two key parameters, the ultimate resistant force pult and the displacement y50, where 0.5 pult is reached, of embankment p-y models as functions of abutment geometry (wall width and height, embankment fill height, etc.) and soil material properties (wall-soil friction angle, soil friction angle, and cohesion). In order to account for the kinematic and site responses, depth-varying ground motions are derived and applied at the free-end of p-y springs, which reflects the amplified embankment crest motion. The modeling approach is applied to simulate the seismic responses of the Painter Street Bridge and validated through comparisons with the recorded responses during the 1992 Petrolia earthquake. It is demonstrated that the flexibility and motion amplification at end abutments are the most crucial modeling aspects. The developed p-y models and the modeling approach can effectively predict the seismic responses of highway bridges. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The article reflects on the changes that have been implemented to seismic design practice in California. It states about the seismic design criteria of the California Department of Transportation (Caltrans). It mentions the changes which include improvement in retrofit procedures, developing criteria for earthquake-resistant elements and changes in the joints of bridges.

Investigative reports on the 1994 Northridge earthquake in California indicated significant damage experienced by skewed highway bridges. Specifically, the damage sustained by the Pico-Lyons Bridge near Newhall, California, was noted to have been triggered by the skewed geometry of the bridge. In an effort to portray the behavior of this bridge analytically, a series of simulation studies was conducted using nonlinear finite-element analyses. The objective was to demonstrate that certain damage potentials in skewed bridges during earthquakes can be captured analytically. Dynamic time history and pushover analyses were used to capture the behavior of the superstructure of the skewed bridge using the Northridge ground motion record as the input seismic force. Results from the simulation studies showed that potential damage areas, comparable to those reported in the field investigation of the Pico-Lyons Bridge, can be portrayed through analytical modeling. The study also provided the percentage increase in critical stresses in the superstructure of skewed bridges as the angle of skew increases compared with a comparable nonskewed bridge. The study showed that cases in which the angle of skew is approximately 40°, the percentage increase in stress due to the skewness effect at the end girders can be as high as 50-60%. [ABSTRACT FROM AUTHOR]

The article discusses the content of Chapter 6 of the California Legislature that was amended in response to the closure of the Martin's Ferry Bridge signed by California Governor Arnold Schwarzenegger and the Humboldt County. Schwarzenegger has declared a state of emergency to reconstruct the bridge worth 12 million dollars with fund from the federal government and the State of California under the Emergency Services Act. Moreover, the act has provided emergency program to direct the governor and local governing bodies to respond to natural, man made or war-caused emergencies with support from the Office of Emergency Services to facilitate the administration of emergency programs.

The Golden Gate Bridge is one of the best-known engineering structures in the world and was the longest suspension bridge in the world for many years. Its design has generally been attributed to Joseph Strauss, but recent evidence proves that Charles Ellis was the prime designer of the bridge between 1929 and 1931. Strauss fired Ellis in late 1931 and systematically removed any mention of Ellis’ name in his final report on the bridge issued in 1938. It remained for John van der Zee in his book The Gate to set the record straight. This paper makes the case that Strauss violated one of the fundamental ethical canons—that of giving credit where credit is due. [ABSTRACT FROM AUTHOR]

The article highlights the construction and features of the 1-km-long and four lane highway Otay River Bridge in San Diego County, California. The author stated that the bridge, which highlights a combination of ingenuity and design is the second bridge to employ segmented precast concrete segmental construction. In addition, the bridge design incorporates lean lines and curving edges to mimic the natural setting of the region and in response to the environmental goals of the project. She emphasized that the bridge has been built using the balanced-cantilever method.

Compression tests were conducted on two reduced-scale orthotropic plates to verify the design strength of steel box girders for the new San Francisco–Oakland Bay Bridge. The first specimen was composed of three longitudinal closed ribs and a top deck plate. It failed in global buckling, followed by local buckling in the deck plate and ribs. The second specimen, which was composed of four longitudinal T-shaped ribs and a bottom deck plate, experienced global buckling as well as local buckling in the ribs and the deck plate. The ultimate strength and failure mode of both specimens were evaluated by two bridge design specifications: the 1998 AASHTO load and resistance factor design specification and the 2002 Japanese JRA specification. Findings from code comparisons showed that: (1) Sufficient flexural rigidity of ribs were provided for both specimens; (2) the JRA specification slightly overestimated the ultimate strength of both specimens; and (3) neither specifications predicted the observed buckling sequence in Specimen 2. A general-purpose nonlinear finite element analysis program (ABAQUS) was used to perform correlation study. The analysis showed that the ultimate strength and postbuckling behavior of the specimens could be reliably predicted when both the effects of residual stresses and initial geometric imperfections were considered in the model. [ABSTRACT FROM AUTHOR]

Abstract: California is in a highly seismically active region, and structures must be designed and constructed to withstand earthquakes. Seismic hazard analysis to estimate realistic earthquake ground motions and surface fault rupture offsets is done for various mitigation measures. The best policy is to avoid constructing structures crossing seismogenic faults. Because earthquake timings are unpredictable within our current understanding, the best method is time-invariant deterministic seismic hazard analysis (DHSA) to assess effects from the largest single earthquake called Maximum Credible Earthquake (MCEs) expected from seismogenic faults. Time-dependent hazard estimates such as those arrived at through probabilistic seismic hazard analysis (PSHA) are inherently unreliable. Hazard analyses based on MCEs have been in continuous use for the design and construction of highways and bridges in California for over 30 years. This paper presents an alternative to other methods of analysis, e.g., Abrahamson (2000) [Abrahamson, N.A., 2000. State of the practice of seismic hazard evaluation. Melbourne: proceedings of GeoEng, 2000]. [Copyright &y& Elsevier]

The proposed new east bay crossing of the San Francisco - Oakland Bay Bridge (SFOBB) will use steel shear links as energy dissipators for added protection during strong earthquakes. These large-capacity, built-up shear links are embedded at various heights in the tower, which comprises four vertical steel shafts that are cantilevered from the pile cap. Although A709 HPS 70 steel is used throughout the bridge, the shear links use A709 Grade 50 steel, due to a lack of data regarding the inelastic performance of the HPS 70 steel at large plastic strains. Inelastic shear links have been used in building construction for many years but their application to bridge structures is still in its infancy. For this reason, the California Department of Transportation (Caltrans) funded both full-scale and half-scale tests of the proposed SFOBB shear links. The full-scale test was carried out at the University of California in San Diego, and the half-scale test, which included sections of the adjacent tower shafts, was carried out at the University of Nevada in Reno (UNR). Both tests demonstrated the adequacy of the design by T.Y. Lin, with rupture occurring at about 11% shear strain, well above the minimum required value of 3%. This paper presents the results of the UNR tests and describes a subsequent study which compares this performance with that obtained from a series of follow-on experiments using links fabricated from a high-performance steel (HPS 70) and two different low-yield-point steels (LYP 100 and LYP 225). It is shown that the HPS link performed as well as the Grade 50 link with 32% less overstrength at high inelastic strains. Failure in both cases was initiated at the welds between the stiffeners and the web. It was also found that the stiffeners may be eliminated altogether if thicker webs and low-yield-point steels are used (for the same nominal shear capacity). These LYP links demonstrated a very high capacity for inelastic strain, due to the significant reduction in welding in areas with high plastic yield strains. Failure occurred at about 20% strain. These results also appeared to be independent of the load sequence used to reach failure. Overstrength was observed to be of the same order of magnitude as for the Grade 50 links. The paper concludes that inelastic shear links are very efficient energy dissipators and can be designed to have a high tolerance for inelastic strain. Applications to long-span bridges are attractive because of their low cost and negligible maintenance requirements. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) highway bridges are primary lifeline infrastructures where accurate seismic structural analysis is essential to ensure the safety of bridges. The nonlinear seismic behavior of bridge structures generally exhibits distinct differences in the longitudinal and transverse directions, and thus studies on bi-directional ground motion excitation are needed. Performance-based earthquake engineering (PBEE) methodology explicitly takes into account uncertainties in hazard, structural response, damage, and loss estimation such that enables a comprehensive understanding of the structural performance in a probabilistic manner. For a given large ground motion scenario, this study takes advantage of the PBEE methodology (the first two stages of hazard and structural response) to develop a benchmark probability distribution of the seismic demands (PDSD) for a given bridge structure considering different assumed intercept angles of the input ground motions with the bridge longitudinal axis. The accuracy and reliability of the PDSD estimates from various ground motion selection and modification procedures for the purpose of future bridge designs are evaluated against this reference benchmark PDSD. Such an evaluation is conducted for several engineering demand parameters of three representative RC bridges in California. • GM selection and modification methods are probabilistically evaluated for RC bridges under bi-directional GM excitation. • A benchmark probabilistic distribution of seismic demands (PDSD) is developed for three representative RC highway bridges. • Different intercept angles are considered and their effects in estimating the PDSDs are investigated. [ABSTRACT FROM AUTHOR]

Examines a modular multilane steel freeway bridge in California constructed from surplus railroad flatcar decks. California Department of Transportation's conduction of static-load testing and computer dynamic analysis; Use of the structure for emergency freeway bridge repair; Potential to provide a bridge that can withstand severe earthquake aftershocks.