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Collision on a Pole Found in Soil
Published in Arnold C.Y. Yong, Nelson T.K. Lam, Scott J. Menegon, Collision Actions on Structures, 2023
Arnold C.Y. Yong, Nelson T.K. Lam, Scott J. Menegon
A pole can be secured to the ground by having it embedded into soil, or by casting the pole into a concrete base slab forming a pole-slab assemblage that is then placed in a shallow pit. The mechanism of the two types of poles in withstanding a collision is very different. With a soil-embedded pole, the design approach is to treat the pole as a flexible element that responds to a collision action mainly by flexure. A compact section can be chosen in order to safeguard against premature failure by local buckling, or by shear. Guidelines in relation to the required depth of embedment of the pole into the subgrade have been provided. With a free-standing pole-slab assemblage, the stability to resist overturning is by virtue of the self-weight of the concrete slab. With both design approaches, algebraic expressions for predicting the maximum displacement and slope of deflection of the pole for a given collision scenario have been presented. Both design methodologies are illustrated with worked examples.
Stand-Alone Photovoltaic Systems
Published in Roger Messenger, Homayoon “Amir” Abtahi, Photovoltaic Systems Engineering, 2017
Roger Messenger, Homayoon “Amir” Abtahi
Figure 7.5 shows a parking lot for which it is desired to provide an average illumination of 2 FC. The figure also shows suitable locations for fixtures and an approximate lighting pattern that would be obtained with a well-designed sharp cut-off fixture. The fixture has a CU of 0.8 and a MF of 0.9. The sharp cut-off feature of the fixture helps to prevent spillage of light onto adjacent property, so it will be assumed that any loss of light to adjacent property will be accounted for by the CU. The lot measures 160 ft (48.8 m) × 160 ft, so the total area of the lot is 25,600 ft2 (2378 m2). With the spacing of the fixtures as shown, the distance between fixtures is 113 ft (34.4 m). For parking lots, the spacing of lighting poles is typically set at 4 pole heights. Thus, in this case, the pole height should be approximately 28 ft (8.5 m).
Poles, Cross Arms, Pins, Racks, and Insulators
Published in Anthony J. Pansini, Electrical Distribution Engineering, 2020
Much of the difficulty experienced with wood poles is due to decay, particularly at the ground line. Decay is caused by fungi attacking the wood fibers, and the conditions most favorable to the growth of decay fungi are air, moisture, and heat, with the wood acting as their food supply. In the part of the pole below ground, moisture is usually present but air is in short supply; in the part above ground, the reverse is generally true. At and near the ground line, both of these elements exist in relatively substantial quantities and, hence, this particular area is more subject to decay.
Investigating the Effects of Climate Change on Material Properties and Structural Performance
Published in Structural Engineering International, 2022
Andre Orcesi, Alan O'Connor, Emilio Bastidas-Arteaga, Mark G. Stewart, Boulent Imam, Katerina Kreislova, Franck Schoefs, Olga Markogiannaki, Teng Wu, Yue Li, Abdullahi Salman, Lara Hawchar, Paraic C. Ryan
Deterioration over time for timber structures has been incorporated into previous studies. Decay models are based on in-field or in-lab measures and report results for specific wood species and climatic conditions.55 Decay models developed for above-ground conditions include those of Leicester et al.,56 Isaksson et al.57 and Viitanen et al.58 Decay models for timber in ground contact are relatively rare. Reference [59] developed a decay model based on field data from 13,940 poles ranging from age 1 to 79 years. About 8% of the poles showed various degrees of decay. Reference [60] developed a decay model for wood in ground contact using in-field data from 77 commonly used commercial timber species buried at five test sites in eastern and southern Australia over a 35-year period. The developed model is a function of the type of timber, mean annual rainfall (including the number of dry months in a year), and the mean annual temperature. Reference [61] used this model to assess the effects of decay on the structural capacity of both treated and untreated timber power poles, with the effects of deterioration and network maintenance incorporated in the analysis. Reference [62] also used this model to study the impact of climate change on the decay rate of timber utility poles. Timber has been the material of choice for supporting power distribution lines around the world. For example, there are between 160 and 180 million timber poles in the USA worth billions of dollars.63 Timber poles are preferred over other materials because they are relatively cheap to purchase, lighter and easier to transport, easy to climb and non-conductive, making them safer for utility workers.63 However, timber poles are susceptible to decay, which usually occurs at or just below ground level. The decay rate of timber poles is expected to be affected by climate change, which can increase the decay rate. Such an increase will require utility companies to invest more in periodic inspection and replacement of poles.