LONG-TERM END-SLIP MEASUREMENTS AND CORRESPONDING TRANSFER LENGTHS IN PRETENSIONED CONCRETE RAILROAD TIES FABRICATED WITH 15 DIFFERENT REINFORCEMENTS

摘要

Fifteen different reinforcements that are widely employed in manufacturing of railroad ties worldwide were selected for the study presented in this paper. Selected reinforcements include; 12 number of 5.32 mm diameter wires, two 3/8-inch diameter 7 wire strands, and one 5/16-inch diameter 3 wire strand. Twelve wire reinforcements are differed by surface indent geometries with one wire being smooth surfaced profile. Strand reinforcements consisted one smooth and one indented 7 wire strand, and one smooth 3 wire strand. All reinforcements were stored in low-humidity environment to avoid rust. Later, pre-tensioned concrete railroad ties were fabricated at a tie manufacturing plant with the selected 15 different reinforcements in January 2013. Same concrete mix proportions were used during the fabrication of the ties with these 15 reinforcement types. Reinforcement end-slips were measured for each concrete tie at every reinforcement location during August 2014 (after one and half years). Simultaneously, transfer length measurements were measured on all these ties through surface strain measurements. Detailed analysis of the measured end-slips for the ties fabricated with 15 reinforcements is presented. This analysis includes the variation of end-slip measurements at different locations in the cross-section. Variation in end-slip measurements for different types of reinforcements is also discussed. Transfer lengths are compared with end slip measurements and an equation to predict transfer lengths from long term end-slip values is presented.