PSI - Issue 64

Pat Rajeev et al. / Procedia Structural Integrity 64 (2024) 523–530 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

524

2

1. Introduction A cable stay is an essential component of a utility pole system which serves the purpose of providing lateral stability. Utility poles are widely used in power distribution and telecommunication sectors around the world. Australia is estimated to have around 5 million timber utility poles in use, whereas North America features over 100 million timber utility poles (Francis and Norton, 2006). Most of these utility poles are designed to be supported by cable stays. Utility poles act as cantilever structures partly embedded in ground. A cable stay consists of a steel cable and rod system that ties the pole to the ground. Fig.1 (a) shows a photo of a pole system with a cable stay. It can be observed that the cable stay provides rigid support to the pole to ensure stability while preventing overturning. The lateral wind forces exerted directly on the pole, along with the corresponding alternating uplift and drag forces on the overhead cables caused by the wind, tend to create unfavourable loads that can impact the stability (Darestani, 2016). The primary purpose of the cable stay is to mitigate and address these critical loads, specifically addressing the challenges posed by lateral wind forces. Steel anchor rod of the cable stay is anchored to the ground using different anchor mechanisms and a drawing of the cable stay arrangement is illustrated in Fig.1(b). This drawing shows that the steel rod of the cable stay sytem is an chored to a bed log. The burrial depth of the bed log and its’ dimensions need to be determined at the design stage as per appropriate standards and specifications. Alternatively to bedlog anchoring, screx anchors are also used to provide ground support to the steel rod of the cable stay as illustrated in Fig.2(b). Typically, the inclination of the cable stay is used as 45 0 or 60 0 depending on the design.

(a)

(b)

Fig. 1. (a) Photo of a pole system with a cable stay (b) drawing of the cable stay arrangement

As a steel structure, corrosion is inevitable in cable stays. Therefore, cable stays deteriorate over service life affecting the structural integrity. The thimble and the flexible cable segment of the stay are positioned above ground level, while the steel rod and the anchoring segment of the stay are situated below ground level. When examining corrosion levels above and below ground, there is a notable increase in corrosion rates in the below-ground segment of the cable stay. This is primarily attributed to favourable conditions that promote corrosion. In contrast to the atmospheric moisture content in the above-ground area, the below-ground sections trap and retain moisture for longer durations, thereby intensifying the corrosion process (Zamanzadeh et al., 2007). Corrosion reduces the effective cross-