Editor's Note

This issue of the Journal begins with three papers on traffic-induced vibrations. The first two papers are companion papers by Calcada, Cunha, and Delgado. “Analysis of Traffic Induced Vibrations in a Cable-Stayed Bridge. I: Experimental Assessment” discusses the experimental approach that was used to evaluate traffic induced dynamic effects in the Salgueiro Maia cable-stayed bridge. The tests evaluated the dynamic amplification factors under the passage of individual heavy trucks as well as groups of heavy trucks in various lanes and at different speeds. In “Analysis of Traffic Induced Vibrations in a Cable-Stayed Bridge. II: Numerical Modeling and Stochastic Simulation” the authors continue with their work on the Salgueiro Maia cable-stayed bridge by developing a numerical model to simulate the dynamic response of the bridge. Further, stochastic Monte Carlo simulations of the dynamic responses were used to evaluate dynamic amplification factors, taking into account the randomness of different factors associated with characteristics of the pavement, the vehicles, and the traffic flow.

The final traffic induced vibration paper is “Train-Induced Vibration Control of High-Speed Railway Bridges Equipped with Multiple Tuned Mass Dampers” by Lin, Wang, and Chen. This paper investigates the use of multiple tuned mass dampers to suppress train-induced vibration on railway bridges. The authors found that according to the train load frequency analysis, resonant effects will occur as the modal frequencies of a bridge are close to the multiple of impact frequency of the train load. Numerical results from simply supported bridges under real trains showed that the proposed multiple tuned mass dampers were more effective and reliable than a single tuned mass damper.

This issue continues with three seismic papers. The first, “Modal Property Changes of a Seismically Damaged Concrete Bridge,” by Bolton, Sikorsky, Park, Choi, and Stubbs describes the modal changes that occurred on the Lavic Road Bridge after an earthquake. Prior to the seismic event, periodic modal field tests were conducted on the structure to evaluate the impact of on-going reactive-aggregate induced structural deterioration. One of these tests was performed $2\text{weeks}$ before the earthquake. A test was conducted $3\text{days}$ after the event in order to capture any changes in the structure’s modal properties that might have resulted from damage incurred as a result of the event.

The second seismic paper is by Dicleli, Mansour, and Constantinou. In “Efficiency of Seismic Isolation for Seismic Retrofitting of Heavy Substructured Bridges” the efficiency of seismic isolation for the seismic retrofitting of bridges with light superstructures and heavy substructures is studied. The results found that the bearings and substructures of these types of bridges need to be retrofitted. Retrofitting the bearings versus replacing the bearings with seismic isolation bearings was investigated, and it was found that the use of seismic isolation bearings was significantly less costly than retrofitting the existing bearings.

The third and final seismic paper, “Seismic Modeling of Skewed Bridges with Elastomeric Bearings and Side Retainers,” by Maleki compares the seismic response of straight and skewed slab-girder, single-span bridges with varying gap distances between the elastomeric bearing and side retainers. The behavior is nonlinear, and the study shows that ignoring this nonlinear behavior can lead to erroneous results.

Engineers managing existing bridges and transportation systems will find the next three papers of potential interest. Sirca and Adeli in “Case-Based Reasoning for Converting WSD-Based Bridge Ratings to LFD-Based Ratings” present a methodology and an intelligent decision support system to aid in the conversion of working stress design-based bridge ratings to a load factor design-based rating system. The system uses an artificial intelligence approach to case-base reasoning to aid the work.

“Overview of a Modal-Based Condition Assessment Procedure” by Wang et al. summarizes a condition assessment procedure based on a complete system of field testing, finite-element modeling, and load rating. Modal testing and truck load testing are used to collect measurements of constructed systems. Varying physical parameters of finite-element models are adjusted during calibration to achieve convergence between the experimental measurements and the analytical results in order to develop a bridge load rating from the calibrated model.

The final paper in this group is authored by Liu and Frangopol. In “Balancing Connectivity of Deteriorating Bridge Networks and Long-Term Maintenance Cost Through Optimization” the authors present a network-level bridge maintenance planning problem as a combinatorial optimization that is automated by a genetic algorithm to select and allocate maintenance interventions of different types among networked bridges over a specified period of time. The paper shows that the proposed maintenance planning procedure satisfactorily prioritizes scarce maintenance needs to the deteriorating bridges that are most critical, as well as cost effectively distributing maintenance interventions over the specified time horizon.

The tenth paper of this issue provides the results of an investigation of bridge approach slabs and their supporting soils. Cai, Shi, Voyiadjis, and Zhang in “Structural Performance of Bridge Approach Slabs under Given Embankment Settlement” show the development and present a means to correctly design an approach slab that considers the interaction between the approach slab and the supporting embankment soil underneath.

The final paper of this issue of the Journal is titled “Experimental Study on Moment-Plastic Rotation Capacity of Hybrid Beams” by Ito, Nozaka, Shirosaki, and Yamasaki. In this paper the moment-inelastic rotation behavior of hybrid steel girder bridges is experimentally investigated. Inelastic rotation capacities are experimentally obtained and then are compared with predicted moment-inelastic rotation curves by White and Barth. It was concluded that hybrid girders have a greater deformation capacity then homogeneous ones and that the prediction curve is more conservative for girders with a higher web slenderness ratio.

The discussion and closure in this issue is in regards to “Dynamic Behavior of Deck Slabs of Concrete Road Bridges” by Broquet, Bailey, Fafard, and Brühwiler. In his discussion, Gilbert H. Béguin asks several questions about the analysis and testing and concludes that the extensive modeling that was performed by the authors should be experimentally evaluated. In the closure for “Dynamic Behavior of Deck Slabs of Concrete Road Bridges” the authors address Mr. Béguin’s questions.