Editor’s Note

The July 2009 issue of the ASCE Journal of Bridge Engineering begins with a paper on the variable-amplitude fatigue strength of structural steel details. “Variable-Amplitude Fatigue Strength of Structural Steel Bridge Details: Review and Simplified Model” by Albrecht and Lenwari reviews eight previous studies on the variable-amplitude fatigue strength structural steel details. The review found that the variable-amplitude data correlated well with the constant-amplitude data when the variable-amplitude data are plotted in terms of an equivalent root-mean-cube stress range. Based on the results, the authors suggest that the current AASHTO equations be replaced with a single equation similar to the equation used to predict the fatigue crack growth rate in metals, as the simplified model more accurately predicts the fatigue life near the variable amplitude fatigue limit.

Barth and Roberts in “Flexural Capacity of Compact Composite I-Girders in Positive Bending” present an assessment of the behavior of composite positive bending specimens. Recent experimental tests coupled with finite-element analysis and mechanistic evaluations of the cross-section flexural capacity suggest that larger capacities could be achieved from AASHTO’s equations. A less conservative design moment capacity expression developed from this assessment is provided.

The third paper in this issue of the Journal is “Load Rating and Reliability Analysis of an Aerial Guideway Structure for Condition Assessment” by Shmerling and Catbas. The purpose of the paper is to present a study of the structural behavior and capacity used up in an existing guideway structural system that has been in service for about $35\text{years}$ . The critical parameters were material properties, prestress losses, boundary condition, and continuity conditions. The information from their work can be used for improved inspection and for the development of long-term structural monitoring.

Liu, Frangopol, and Kim in “Bridge Safety Evaluation Based on Monitored Live Load Effects” present a new approach to evaluating the safety of existing bridges based on monitored structural responses and component conditions. A limit state equation is developed for the measured strain data from the monitoring system. With the addition of new concepts—the condition function and the performance function—the monitoring information is integrated into the structural safety evaluation. The result is a life-cycle cost-oriented and reliability-based infrastructure management system using structural monitoring.

Yan and Chang propose a two-step assessment methodology for cable-stayed bridges in “Vulnerability Assessment of Cable-Stayed Bridges in Probabilistic Domain.” Based on a hypothetical single-tower cable-stayed bridge the authors show that the proposed method provides a quantitative tool for analyzing the vulnerability performance of this type of bridge as a result of a terrorist event.

In “3D Coordinating Relations between Steel Cables and Concrete of Prestressed Concrete Beam Bridges,” He et al. present a method to address the interaction between steel cables and concrete in curved prestressed concrete bridges. Their method utilizes the grillage structure finite-element method.

The final paper in this issue is another historical paper by Griggs, “Thomas C. Clarke, Bridge Builder.” The paper highlights one of the leading engineers in North America who worked on railroads, waterways, buildings, and bridges. Clarke was a leader in the formation and running of several major bridge design and construction companies, served ASCE for many years beginning as a director in 1870, and was elected president of the Society for 1896–1897.