Journal of Bridge Engineering

Slender long-span bridges exhibit unique features which are not present in short and medium-span bridges such as higher traffic volume, simultaneous presence of multiple vehicles, and sensitivity to wind load. For typical buffeting studies of long-span bridges under wind turbulence, no traffic load was typically considered simultaneously with wind. Recent bridge/vehicle/wind interaction studies highlighted the importance of predicting the bridge dynamic behavior by considering the bridge, the actual traffic load, and wind as a whole coupled system. Existent studies of bridge/vehicle/wind interaction analysis, however, considered only one or several vehicles distributed in an assumed (usually uniform) pattern on the bridge. For long-span bridges which have a high probability of the presence of multiple vehicles including several heavy trucks at a time, such an assumption differs significantly from reality. A new “semideterministic” bridge dynamic analytical model is proposed which considers dynamic interactions between the bridge, wind, and stochastic “real” traffic by integrating the equivalent dynamic wheel load (EDWL) approach and the cellular automaton (CA) traffic flow simulation. As a result of adopting the new analytical model, the long-span bridge dynamic behavior can be statistically predicted with a more realistic and adaptive consideration of combined loads of traffic and wind. A prototype slender cable-stayed bridge is numerically studied with the proposed model. In addition to slender long-span bridges which are sensitive to wind, the proposed model also offers a general approach for other conventional long-span bridges as well as roadway pavements to achieve a more realistic understanding of the structural performance under probabilistic traffic and dynamic interactions.

A new beam-to-column connection has been developed for assembling precast concrete bridge bents in regions of high seismicity. The connection is made with a small number of large column bars, which are grouted into large corrugated-metal ducts embedded in the cap beam. Bents built with these connections can be erected quickly and permit generous construction tolerances. To evaluate the seismic performance of the proposed connection, lateral-load tests were performed on three manifestations of the connection, as well as on a comparable cast-in-place connection. The tests demonstrated that the force-displacement response and damage progression in the precast connection are similar to those of typical cast-in-place concrete connections. Deliberate partial debonding of the longitudinal reinforcement only slightly affected the force-displacement response and observed damage.

Nonlinear dynamic analysis with fiber-element models is now widely used to assess the seismic response of bridge structures. The ability of such models to accurately simulate response parameters for characterizing the postearthquake condition of bridges, namely residual displacements, is assessed by comparison of analyses of dynamically loaded reinforced concrete bridge columns to experimental data. The models are unable to capture residual displacements, and the cause of the inability to capture residual displacements is investigated through dynamic analysis of fiber-element and single-degree-of-freedom (SDOF) models. A certain type of pinching present in the numerical hysteretic response shape is found to lead to poor residual displacement simulation both in the SDOF models and in fiber-element models. When eliminating this pinching, improvements to residual displacement simulation are found. A modified concrete constitutive model representing damage accumulation from cyclic loading is implemented for the fiber-element analysis that incorporates changes to reloading behavior when moving from high tensile strain back to compression. Analysis using the modified concrete constitutive model leads to improvements in the ability of the fiber-element model to capture residual displacements.

An asphalt plug joint (APJ) is a type of expansion joint providing quick, easy, and cheap installation along with good surface flatness. However, APJs are known to suffer from premature failure, and their behavior, especially under thermal movement, has not yet been fully established. In this paper, the behavior of a typical APJ subjected to thermal and traffic loads is examined through a series of finite element analyzes employing a temperature-dependent viscoplastic material model. The material parameters are calibrated by using previously published test data, and the model is validated by comparing simulated responses to APJ test data. The developed models are then used to investigate stress and strain distributions, vulnerable locations to cracking failure, and local demands at those locations when a prototype APJ is subjected to various loading and temperature conditions. Sensitivity studies are also conducted to quantify the effect of debonding the bottom of the APJ and loading rate. The model results shed light about APJ response under traffic and thermal loading and provide new, fundamental information that can be used to improve the durability of APJs. For example, the simulation results suggest that intentionally debonding the interface between the gap plate and the APJ is a practical and low cost solution to mitigate the risk of premature APJ failure.

The response surface Monte Carlo method (RSMCM) is proposed for reliability analysis of aerostatic response and aerostatic stability for different types of long-span bridges, in which the nonlinear effects due to geometric nonlinearity and deformation-dependent aerostatic loads are taken into consideration. The geometric parameters, the material parameters, and the aerostatic coefficients of the bridge girder are regarded as random variables in the proposed method. RSMCM has higher accuracy in comparison with the traditional response surface method and requires much less computational cost than the conventional Monte Carlo method. The proposed method is applied to reliability analysis of aerostatic response and aerostatic stability of the Hong Kong Ting Kau Bridge, and reasonable results illustrating effectiveness of the method are obtained.

A numerical model has been developed to investigate the dynamic characteristics of the Maglev system. Modeling of the guideway with the surface irregularity and modeling of the Maglev vehicle are described. Numerical simulations are performed in Simulink to solve the coupled problem. Based on this model a study focused on the dynamic characteristics of the guideway and the vehicle/guideway interaction has been made. The effects of various approaches to model the Maglev vehicle at different levels of accuracy are also investigated. The numerical results are compared with the corresponding values given by MSB-AG-Fahrweg. The conclusions derived by the research are presented in the end of this article.

One of the key assumptions in inelastic design is that members have adequate ductility to allow moments to redistribute. However, while AASHTO specifications contain moment redistribution provisions for steel I-girders, the amount of ductility that is adequate for this specific design situation has not been studied in detail. As a result, the scope of these specifications is limited to beam types known to have significant ductility, which restricts the use of these procedures and causes negative economic consequences. The goal of this work is to determine ductility requirements specifically applicable to AASHTO moment redistribution procedures that are valid for all I-girders. This is accomplished through an analytical procedure, detailed herein. The results of this work are empirical equations predicting the amount of rotation required as a function of the intended level of moment redistribution as well as the material properties and span configuration of the girder. With these requirements known, there is a basis for reducing the overly conservative nature of the existing AASHTO moment redistribution specifications.

The use of glass fiber-reinforced polymer (GFRP) bridge decks is appealing for applications where minimizing dead load is critical. This paper describes fatigue and strength testing of two types of GFRP decks being considered for use in the retrofit of an aging steel arch bridge in Snohomish County, Washington, where a roadway expansion is necessary and it is desirable to minimize the improvements to the arch superstructure. Each test used a setup designed to be as close as practicable to what will be the in situ conditions for the deck, which included a 2% cross slope for drainage. The fatigue testing consisted of a single 116 kN (26 kip) load applied for 2 million cycles, which corresponds to an AASHTO HS-25 truck with a 30% impact factor, and the strength testing consisted of multiple runs of a monotonically applied minimum load of 347 kN (78 kips). Results from the fatigue testing indicated a degradation of the stiffness of both deck types; however, the degradation was limited to less than 12% over the duration of loading. Further, the results showed both deck types accumulated permanent deck displacement during fatigue loading and one deck type used a detail with poor fatigue performance. That detail detrimentally impacted the overall deck performance and caused large permanent deck deformations. It was also found that degradation of composite behavior between the deck and girders occurs during fatigue loading and should be included in design.

Abutment-backfill soil interaction can significantly influence the seismic response of bridges. In the present study, we provide numerical simulation models that are validated using data from recent experiments on the lateral response of typical abutment systems. Those tests involve well-compacted clayey silt and silty sand backfill materials. The simulation methods considered include a method of slices approach for the backfill materials with an assumed log-spiral failure surface coupled with hyperbolic soil stress-strain relationships [referred to as “log-spiral hyperbolic (LSH) model”] as well as detailed finite-element models, both of which were found to compare well with test data. Through parametric studies on the validated LSH model, we develop equations for the lateral load-displacement backbone curves for abutments of varying height for the two aforementioned backfill types. The equations describe a hyperbolic relationship between lateral load per unit width of the abutment wall and the wall deflection and are amendable to practical application in seismic response simulations of bridge systems.

Due to limited resources, structural health monitoring (SHM) of highway bridges has to be integrated in structural performance assessment in a cost-effective manner. The instrumentation and the long-term SHM procedures are generally chosen with emphasis on most critical bridge components for a particular failure mode. However, global structural analysis is necessary to obtain useful structural performance information. It is then a major challenge to use monitoring data at some locations to perform a structural reliability analysis at other locations. In this paper, a methodology for lifetime serviceability analysis of existing steel girder bridges including crawl tests and long-term monitoring information is presented. The case where the initial goal of monitoring is to provide data for a fatigue analysis of some bridge components is considered. The monitoring results are used to perform a structural reliability analysis of different sections that are critical considering serviceability of the bridge. Limit state equations are used firstly by adhering to the load and strength formulas and requirements set forth in AASHTO specifications, and secondly by integrating monitoring information. Serviceability with respect to permanent deformation under overload is estimated for the girders with these two different methods and a time-dependent performance analysis is conducted by considering corrosion penetration. The proposed approach is applied to the I-39 Northbound Bridge over the Wisconsin River in Wisconsin. A monitoring program of that bridge was performed by the Advanced Technology for Large Structural Systems Center at Lehigh University.

This paper focuses on an investigation of improved continuous longitudinal joint details for decked precast prestressed concrete girder bridge systems. Precast concrete girders with an integral deck that is cast and prestressed with the girder provide benefits of rapid construction along with improved structural performance and durability. Despite these advantages, use of this type of construction has been limited to isolated regions of the United States. One of the issues limiting more widespread use is a perceived problem with durability of longitudinal joints used to connect adjacent girders. This paper presents the results of a study to assess potential alternate joint details based on constructability, followed by testing of selected details. Seven reinforced concrete beam specimens connected with either lapped headed reinforcement or lapped welded wire reinforcement were tested along with a specimen reinforced by continuous bars for comparison. Test results were evaluated based on flexural capacity, curvature at failure, cracking, deflection, and steel strain. Based on the survey and the experimental program, a headed bar detail with a 152 mm (6 in.) lap length was recommended for replacing the current welded steel connector detail.

The bridge rating used in bridge management systems commonly uses only a structural condition. Factors such as seismic risk, hydraulic vulnerability, and strategic importance are commonly used in an isolated fashion. However, these factors are relevant when there is no possibility to calibrate deterioration models. This research uses the needs-based framework for developing an integrated bridge index (IBI) as an aid for prioritization and decisions made on maintenance and rehabilitation of bridges. The index weighs the structure distresses, hydraulic vulnerability, seismic risk, and strategic importance of the bridge. The index was calibrated using visual inspection, survey to experts, and regression analysis. After, the index was applied on six bridges placed on a primary road of Chile. To organize visual inspection, bridge inventory, and compute IBI and rank bridges, a software was developed. The calibration of the IBI index shows a correlation of 98% and all the parameters obtained were significant. Further research is needed to integrate cost with the proposed index and allocate maintenance activities.