طراحي و ساخت تراورس هاي دولنگه و مقايسه تحليل آنها با تراورس هاي متعارف

Design and Fabrication of Dowel-Laminated Cross-ties Compared with Standard Ties Analitically

With goal on reducing demand for large diameter logs to cut standard ties out of them and also improving life expectancy of ties through improved treatment, dowel-laminated cross-ties were designed and for practicality evaluation were fabricated. Required half-ties for this study were cut from residues of beech & oak logs which were being cut to produce conventional ties in a saw-mill that manufactures ties only. Each half-tie had a cross-section of 12.5.15 centimeters and a length of 2.6 meters. Totally, 48 half-ties were cut and stickered to dry in a shelter. Standard ties, cut simultaneously with half-ties, were also stickered in the vicinity to estimate their drying time and to evaluate degrading rate as well. After a 95-day period, moisture content (MC) of beech half-ties lowered down to 24% and that of oak to 35% while MC of standard ties was about 31% on average. Twenty dowel-laminated cross-ties were fabricated (by bolting together), weighed and impregnated under conventional treating process in a cylender simultaneous with conventional ties. 15 beech and 5 oak standard ties were also weighed prior to treatment. After impregnation, both dowel-laminated and standard ones were reweighed to calculate retention of preservative in them and an increament core taker samples were taken for penetration comparisons. In beech dowel-laminated ties retention was calculated to be 266.5, in oak 100 and combined beech oak 177.5 kg/m3. The increament core samples showed that half-ties were impregnated thoroughly, but in standard ties this was not deeper than 5 mm. This would indicate that dowel-laminated cross-ties should last in service longer than conventional wooden ties if their mechanical connections do not fail. This is because they are less susceptible to end split checks and split; thus, they-will not decay as fast as those containing untreated wood in their core part.