Editor’s Note

The May 2009 issue of the Journal of Bridge Engineering begins with a paper on the distribution factors for bearing forces in the load and resistance factor design (LRFD) and load factor design (LFD) bridge specifications. Cross, Vaughn, Panahshahi, Petermeier, Siow, and Domagalski in “Analytical and Experimental Investigation of Bridge Girder Shear Distribution Factors” present the results of investigations performed on 12 typical Illinois bridges. These bridges were instrumented as well as analyzed using the LRFD and LFD specifications with respect to the shear forces caused by live loads. The authors’ work found that the LRFD specification procedures yielded results that closely approximated the results from both analysis and experimental testing.

In “Service Life Prediction of RC Bridge Structures Exposed to Chloride Environments,” Cheung, Zhao, and Chan propose environmental condition profiles for use with coastal bridges based on exposure conditions and material properties. These profiles were developed through research that included regional climate characteristics, local climate conditions, and the microclimate variations on concrete surfaces. Using two typical locations, numerical examples are provided to show how the proposed corrosion performance assessment model would be implemented. The paper concludes with the construction of an integral empirical equation along with the general critical material and geometrical parameters.

The third paper in this issue of the Journal of Bridge Engineering is on bridge management systems. Elbehairy, Hegazy, and Soudki in “Integrated Multiple-Element Bridge Management System” present the development of a comprehensive bridge management system that optimizes repair decisions considering multiple bridge elements and large networks of bridges. The principal advantage of their approach is the integration of project-level decisions of the best repair strategies to use on elements of each bridge and the network-level decisions of the most beneficial repair year for each bridge. Their paper describes the multiple-element system, its life-cycle formulation, and its related models for deterioration analysis and repair-cost estimation. System implementation and an example application are presented to show the practicality of the system and its performance on different sizes of bridge networks.

“Global Monitoring of Large Concrete Structures Using Acoustic Emission and Ultrasonic Techniques: Case Study” by Shiotani, Aggelis, and Makishima describes the application of the acoustic emission technique to characterize the structural condition of a concrete bridge. The authors show that the evaluation of acoustic emission activity can provide information about any specific part of a structure that requires attention, and consequently a more detailed examination can then be performed. For this paper, wave propagation velocity was used as a means to evaluate in more detail the condition of the area of the bridge indicated by the acoustic emission analysis.

The final three papers in this issue of the Journal of Bridge Engineering are on seismic-related issues for bridges. Marin-Artieda, Whittaker, and Constaninou in “Experimental Study of the XY-Friction Pendulum Bearing for Bridge Applications” present the results of their experimental studies of an XY-friction pendulum seismically isolated truss-bridge model. The work was performed to study the response under tridirectional excitations and to evaluate the use of XY-friction pendulum bearings for bridges. A truss bridge model was tested on a pair of earthquake simulators using acceleration orbits and near-field earthquake histories. The experimental results showed the effectiveness of this type of bearing as an uplift-prevention isolation system. The bidirectional horizontal response of the small-scale XY-friction pendulum isolation system was coupled due to the internal construction of the small-scale connectors joining the two rails of each bearing and the limited free-to-rotate capacity of the bearings due to misalignment of the isolators during installation.

Both of the final two papers are by Goel and Chopra. In “Linear Analysis of Ordinary Bridges Crossing Fault-Rupture Zones,” the authors present the use of two simplified procedures to provide estimates of peak response that are sufficiently close to the results of an “exact” response history analysis. In their other paper, “Nonlinear Analysis of Ordinary Bridges Crossing Fault-Rupture Zones,” they offer three approximate procedures to provide estimates of seismic demands. The authors believe that the estimates provided by these methods are sufficiently accurate for “ordinary” bridges.