Journal of Bridge Engineering

For some materials, such as RC, there is an initiation phase of deterioration where aggressive agents such as chlorides diffuse into the concrete cover. It is necessary to model this initiation time when attempting to determine the optimal maintenance strategy for the lifetime cost associated with a structure. It has been recommended in the literature that Markov chain models should be further improved within maintenance management systems to take initiation time into consideration. Many existing bridge management systems (BMSs), such as BRIDGIT and Pontis, use Markovian-based maintenance management to simulate the propagation phase of deterioration and repair of structures over time. It is therefore useful to continue this progress through incorporation of an initiation phase in relation to the development of Markovian-based maintenance management, which can lead to an improvement in BMSs that are already in place. The incorporation of the initiation phase into deterioration modeling can affect the frequency of inspections, repairs, and failures and hence the expected cost over the remaining lifetime of the structure. On this basis, this issue was addressed as part of this study. A maintenance management model has been further developed to take this two-step deterioration process (i.e., initiation and propagation) into account. This allows owners/managers of bridges to compare the efficiency of different maintenance strategies in terms of both the initiation phase and the propagation phase of deterioration to determine the optimal maintenance strategy for the structure or group of structures being considered. The capabilities of the developed methodology are demonstrated using a practical example.

Fatigue tests were conducted for corroded galvanized steel wires on three corrosion levels, showing that fatigue strength of corroded wires lowers as corrosion progresses. Corrosion pits were measured on the corroded specimens, showing severer corrosion produced deeper pits in more condensed areas. Fatigue tests were then conducted for wire specimens with artificial pits whose sizes were decided by the measured corrosion pit data. Three different pit shapes were assumed: round, triangle, and triangle with a notch. The wire specimens with round pits did not break until 1 million cycles in the stress range of 400 MPa. The fatigue strength of wires with the triangular pit was lower than that with a round shape. Triangular pit specimens broke at fewer cycles for shorter pit length. The fatigue strength of wires with a notched triangle further decreased, and critical cycles did not depend on pit length. As the $S\text{-}N$ relation of the wire specimens with triangular pits and notched triangular pits has a similar tendency as those of the actually corroded wires, the pit shape seems to be a dominant factor in lowering fatigue strength. The stress concentration factor at the sharp edge of the pits were obtained by strain gauge measurement and FEM analysis. Both methods showed that the stress concentration is larger for sharper pit shapes, indicating that this is the major cause for the decrease of fatigue strength.

This paper describes an investigation to quantify the behavior of a precast deck system. As part of this investigation, a live-load test was performed on a steel I-girder bridge made with accelerated bridge construction precast deck panels. It was found that the bridge was behaving compositely in some locations and noncompositely in others. When the bridge was decommissioned, a two-girder specimen was salvaged and transported to Utah State University for shear-capacity testing. The primary shear failure mechanism was found to be buckling of the girder web. A nonlinear finite-element analysis was conducted using ANSYS that was found to replicate the experimental behavior and reproduce the failure mechanism and magnitude. It was concluded that the effect of the noncomposite behavior on the ultimate shear capacity was a reduction of approximately 8.0%. The measured ultimate capacities were compared with estimates calculated according to procedures in the AASHTO LRFD specifications. When using the specified steel strength, the code predicted shear resistance ranging from 8.0% higher to 0.7% lower.

The seismic behavior of horizontally curved steel bridges is more complex than straight bridges because of their curvature and other parameters. Studies that attempt to develop methods to efficiently predict their seismic response have been somewhat limited to date. A computational modeling approach was examined to assist with understanding the seismic behavior of these bridges. The computational, three-dimensional (3D) bridge models consisting of the concrete deck, steel girders, cross-frames, pier columns and caps, and abutments and footings were created in OpenSees and examined for accuracy via application to a representative, three-span continuous curved steel plate girder bridge in Pennsylvania. Sensitivity studies in the form of tornado analyses were also carried out to investigate the influence of critical curved bridge parameters on the seismic response using a group of representative bridges. Each representative bridge was subjected to an ensemble of synthetic ground motions, and seismic response was examined. Results from the sensitivity study indicated a 17–22% variation in maximum bearing and abutment deformations, column curvature ductility, and cross-frame axial forces parameters for the range of bridge radii and span numbers that were investigated.

This paper presents results based on the analysis of an extensive database of weigh-in-motion (WIM) data collected at five European highway sites in recent years. The data are used as the basis for a Monte Carlo simulation of bridge loading by two-lane traffic, both bidirectional and in the same direction. Long runs of the simulation model are used to calculate characteristic bridge load effects (bending moments and shear forces), and these characteristic values are compared with design values for bridges of different lengths as specified by the Eurocode for bridge traffic loading. Various indicators are tested as possible bases for a bridge aggressiveness index to characterize the traffic measured by the WIM data in terms of its influence on characteristic bridge load effects. WIM measurements can thus be used to determine the aggressiveness of traffic for bridges. The mean maximum weekly gross vehicle weight is proposed as the most effective of the indicators considered and is shown to be well correlated with a wide range of calculated characteristic load effects at each site.

Trucks may simultaneously appear on a highway bridge in the same lane or different lanes, which represent the governing load for short- and medium-span bridges. In practice specifications, the multiple presence factor (MPF) to cover these simultaneous loads was developed using intuition or models without support of measured weight data of trucks in motion. This paper presents a research effort of deriving a MPF based on weigh-in-motion (WIM) truck data, for both the strength and fatigue limit states, including about 68 million trucks gathered for 436 months and from 43 sites in California, Oregon, Michigan, and New York. The resulting MPFs are proposed in this paper as functions of bridge-span length, truck-traffic volume, and number of lanes available. They show that the code-specified MPF values are conservative and sometimes overconservative by 400% or more, which may have caused too high requirements for load-rating existing bridges, especially for shorter spans and low truck traffic. The recommended MPF may be considered to be adopted in specifications for highway bridge design and evaluation. This paper also presents a new truck-by-truck analysis approach for understanding the load effect of trucks in motion, taking advantage of increasingly available WIM data of large quantity to avoid unsupported assumptions in live-load modeling.

This study concentrates on the efficiency of numerous ground motion intensity measures (IMs) to be used in estimating the response of seismic-isolated bridges (SIBs). Efficiency of commonly used IMs was investigated through their correlation with maximum isolator displacement (MID) obtained from nonlinear dynamic analyses. Two sets of ground motions (GMs), classified as ordinary and pulse-like, were used in nonlinear dynamic analyses of SIBs. In the analyses, varying isolation parameters, such as the isolation period, $T$, and the characteristic strength of the isolator, $Q_d/W$, were studied. Sensitivity to varying $T$ and $Q_d/W$ and the effect of ground motion type on the correlation of IMs with MID of SIBs were examined. To improve the correlation of existing IMs, modified IMs were proposed. The results revealed that the isolation period has a pronounced effect on the correlation of IMs with MID of SIBs, especially for pulse-like GMs. Among the investigated IMs, modified velocity spectrum intensity appears to have the strongest correlation with MID of SIBs for a wide range of isolation parameters and ground motion type.

A structural study examines the oldest remaining metal bridge in the Commonwealth of Virginia, a wrought-iron bowstring arch truss, designed and manufactured by the King Iron Bridge Company. Finite-element analysis is used to evaluate the interaction between the arch and truss, and the results are compared with field measurements from a live-load test. The study reveals that diagonal truss elements decrease arch bending by distributing concentrated vertical loads along the arch toward the abutments in a way consistent with that of modern network arch bridges. When the truss diagonals are absent, the vertical bridge-deck deflection is doubled. Underslung portal frames provide lateral stiffness to the arch, an innovation that accommodates a shallow arch profile conducive to transportation and erection.