Douglas L Wood

Evaluation and Field Load Testing of Timber Railroad Bridge

Several spans of a 60-year-old open-deck timber railroad bridge on the Southern Pacific Railroad Line (now the Union Pacific) in Southwest Texas were field tested. The tests were conducted with the sponsorship and cooperation of the Association of American Railroads to determine the vertical live load distribution characteristics of the superstructure. The bridge was originally constructed with Douglas-fir larch solid sawn stringers but was rehabilitated on several occasions to allow comparisons to be made with respect to different rehabilitation options, including the use of a helper stringer and the use of glued laminated timber (glulam) stringers. The test spans measured approximately 4.1 m (13.5 ft) center-to-center of supports and included two closely “packed” chords, each consisting of four timber stringers (one test span included an additional helper stringer added to one chord). One chord was made up of glulam timber and the other was made up of solid sawn timber. The bridge superstructure was generally in satisfactory condition, with some stringer horizontal splitting noted over the bents. The bents were in reasonably good condition, but chord bearing was uneven on bent caps. Static and dynamic deflection load test data were obtained using a special test train. The test results indicate that the glulam chord performed better than the older sawn stringer chord, even when a helper stringer was added. Individual stringers within a chord did not always share the load equally.

Field and Laboratory Testing of Precast Concrete Channel Bridges

The precast channel bridge (PCB) was commonly constructed on Iowas secondary roads approximately 40 years ago. Each PCB span consists of eight to 10 simply supported precast panels ranging in length from 19 to 36 ft. The panels resemble a steel channel in cross section; the web is orientated horizontally to form the roadway deck, and the vertical legs act as shallow beams. Bundled bars in each leg are used for flexural reinforcement. Many of the approximately 600 PCBs in Iowa show signs of significant deterioration. Typical deterioration consists of spalled concrete cover and corrosion of the bundled primary reinforcement. The objective of this research was to assess the structural sufficiency of the deteriorated PCBs through field and laboratory testing. Four deteriorated PCBs were instrumented with strain gauges to measure strains in both the concrete and the reinforcing steel and with transducers to measure vertical deflections. Responses from loaded trucks were recorded and analyzed. Test results rev...