Abstract
As the ability to obtain high-grade material becomes more difficult, assessing the value of under-strength timber for use in maintaining timber railroad bridges has become increasingly important. The objective of this study was to examine, experimentally, the fatigue behavior of under-strength timber railroad bridge stringers. The sample group that was tested included nineteen southern pine solid-sawn stringers that were 178 mm (7 in.) wide by 356 mm (14 in.) deep by 4.8 m (16 ft) long. The commercial grade of the members ranged from below No. 3 to No. 2. All of the members had been pressure treated "to refusal" with creosote. Results from the fatigue tests indicate a substantial variation in the fatigue strength of the members; the slope of the normalized S-N diagram was nearly zero. A natural fatigue limit appeared to be approximately 50-60 percent of estimated fiber bending strength. The failure modes observed were predominantly horizontal shear and tension.
Borchers, Christopher Ryan (2002). Fatigue tests of under-strenghth timber railroad bridge stringers. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2002 -THESIS -B663.