Live-Load Response of Eyebars on a 110-Year-Old Steel Truss Railroad Bridge

Abstract

Eyebars commonly were used as tension members in steel truss railroad bridges, frequently installed in sets of two or more. Eyebars were favored by engineers because they (1) were easy to fabricate, (2) were faster to erect than other shapes, and (3) minimized secondary stresses by allowing freer rotation at joints. Research was conducted to gain a better understanding of the effects of excessive wear on the eyebars and connecting pins of a 110-year-old truss railroad bridges. Eyebar responses to live load were field tested. Strain and accelerometer readings were taken from four different types of passenger trains and at various speeds. Results indicate that different eyebars between the same two panel points frequently were loaded neither simultaneously nor equally. Adverse results of this phenomenon include development of excessive bending and shear stresses in pins, higher axial stress in some bars, and often extreme vibration of bars.