Editor’s Note

The March 2009 issue of the Journal of Bridge Engineering begins with a very timely paper on the failure of the prestressed girders in an existing bridge. Harries in “Structural Testing of Prestressed Concrete Girders from the Lake View Drive Bridge” describes the structural testing and post-test forensic examination of two girders recovered from the partially collapsed Lake View Drive Bridge. On December 27, 2005, the fascia beam supporting the east parapet of the third span of this bridge failed solely under dead load. The paper describes the tests that were conducted and the observations from these tests. It concludes with the conclusions based on the pre- and posttest inspections along with recommendations to reinforce issues that need to be considered in the bridge inspection and rating process of similar structures.

“Numerical Analysis of Continuous Beams Prestressed with External Tendons” by Pisani presents a numerical model that was developed to simulate the behavior up to the point of collapse of continuous concrete beams prestressed with bonded or external tendons. The model has been developed to automatically determine the most suitable extent of each load increment according to the actual stiffness of all the segments that form the discretized beam. The rotational capacity of plastic hinges in nonlinear analysis is a special problem. The author discusses this issue in depth and provides a simple rule that differs from those used in the past and that is used to subdivide the beam into discrete elements. The effectiveness of the numerical model was tested by comparing its output with the results of 14 experimental tests. Good results were obtained.

The next two papers in this issue of the Journal deal with composite materials. The first is by Tanaka, Murakoshi, Nagaya, and Watanabe. In “Static and Fatigue Behavior of Thick Pultruded GFRP Plates with Surface Damage,” the authors describe the issues regarding tests of heavy wheel loads on GFRP bridge decks, the damage to these decks, and their effect on fatigue life. Of significant interest is that although the decks cracked as early as 10% of their total fatigue life, these initial cracks had little effect on the total fatigue life. This result was because of the delamination of the surface layers, which prevented further crack propagation.

The second paper on composites is “Finite-Element Modeling and Development of Equivalent Properties for FRP Bridge Panels” by Cai, Oghumu, and Meggers. Fiber-reinforced polymer (FRP) materials are increasingly being used to reduce the self-weight and provide the necessary stiffness for bridge decks in the form of a sandwich panel. However, because of the geometric complexity of an FRP sandwich deck, convenient analysis and design methods have not been developed. The study described in this paper attempts to develop equivalent properties for a complicated sandwich panel configuration using finite element modeling techniques. The equivalent properties can then be transformed into an equivalent solid orthotropic plate. A procedure for in-plane axial properties and out-of-plane bending properties has been developed.

Itoh and Gu in “Prediction of Aging Characteristics in Natural Rubber Bearings Used in Bridges” describe thermal oxidation tests that were carried out on natural rubber blocks at different elevated temperatures using the modulus profiling method, and, as a consequence, the heterogeneous property profiles of aged rubber bearings were determined. Their work determined that for natural rubber, the properties of the interior portion of the test sample beyond the critical depth do not change. The property variations of the block surface and the interior were quantitatively analyzed, and an appropriate aging model was established for natural rubber bearings.

“Long-Term Response Prediction of Integral Abutment Bridges” by Pugasap, Kim, and Laman present an analytical, long-term response prediction methodology using finite element modeling for integral abutments. Three bridges were instrumented and have been continuously monitored since November 2002, November 2003, and September 2004 to capture bridge responses. An evaluation of the measured responses found that bridge movement progresses over time, significantly affecting static predictions from a long-term perspective. Both 2-D and 3-D FE models were developed to determine an efficient and accurate analysis. The authors found that their predicted soil pressures using FE models were similar to the measured responses. The predicted abutment displacements and corresponding design forces at the end of a simulated $100\text{-}\text{year}$ period indicated that long-term behavior is significant and should be considered in the design of bridges using integrated abutments.

The final paper in this issue of the Journal is a historical paper by Griggs. “Jacob Hays Linville, A Little Known Giant of Civil Engineering” is about a man who was one of the most prolific bridge builders during the period of 1860 to 1880, when railroads began to cross major rivers in the United States. He built several long-span bridges and set the record for railroad truss bridge span length on three occasions with spans of 320, 420, and 520 feet, respectively. He developed the pin-connected Whipple double intersection truss by placing wrought iron links in the lower chord, and built up riveted plate wrought iron upper chords and posts built of two or more wrought iron shapes riveted together.