Saddle systems have been used on recent projects to support the cables in cable-stayed and extradosed bridge structures. A major design consideration for these anchorage systems is the in-service fretting fatigue behaviour of the cables within the pylon saddle. In order to better understand the fatigue behaviour of these anchorage systems, a research project was undertaken, wherein fatigue tests were performed on saddle test specimens, analytical models for calculating displacements and contact forces were developed, and a multiaxial stress-based fretting fatigue model was developed for calculating fatigue life. In the current paper, it is shown how the developed models can be used to perform probabilistic analysis of fretting fatigue life for the purpose of assessing the fatigue reliability of saddle systems, using two approaches -fretting maps, in conjunction with Monte Carlo simulation (MCS) or the multiplicative dimensional reduction method (MDRM).

Saddle systems are a popular method for supporting the cables at the pylons of cable‐stayed bridges. Fretting fatigue failure of bridge stay cables is a major design consideration for saddle systems. Current design provisions require large‐scale tests of these anchoring systems. However, such tests are costly and time‐consuming. With this in mind, the current paper presents a small‐scale fretting fatigue setup to evaluate the fretting fatigue behavior of bridge stay cable wires at saddle supports. In this paper, fretting tests are conducted on bare and galvanized wires. Hourglass samples are then used to evaluate the material properties and plain fatigue performance of the studied wires. Finally, the microstructure of the wires is evaluated, and the influence of defects on the fretting fatigue life of the wires is discussed.

No abstract

In many design codes for roadway bridges, it is required that a design truck be passed over influence lines for stress at various locations on the bridge to obtain nominal stress ranges for design. For the fatigue design of Canadian bridges in the infinite or very long-life domain, the nominal stress range is compared with a fatigue limit, after modification by an appropriate correction factor to account for the difference between the nominal stress range and some measure of the extreme stress range in the expected real traffic histogram, which governs infinite life design. The extent to which the influence of simultaneous truck crossings was considered in the establishment of the correction factors is believed to be limited. With this in mind, a simulation-based study, conducted to investigate the effects of simultaneous vehicle crossings on the fatigue limits for steel bridges under Ontario highway traffic loading, is presented in this paper.

No abstract