Performance evaluation of fiber-reinforced polymer poles for transmission lines

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Ibrahim, Sherif Mohamed
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The increasing demand for pole-type transmission structures has necessitated the utilization of innovative and environmentally friendly materials for such structures. Traditional materials such as wood, steel, and concrete are commonly used to construct electrical transmission and distribution poles. However, the shortage of wooden poles, their short life expectancy, and various environmental concerns have promoted hydroelectric utility companies to search for a cost-effective alternative. Glass Fiber-Reinforced Polymer (GFRP) poles are lightweight. The use of GFRP poles is not new. A number of companies are already involved in the production of such poles. Research in this area, however, is limited. Therefore, a research program was conducted at the University of Manitoba, Canada, to evaluate the performance of tapered GFRP poles and to develop design guidelines for the use of such poles by electric utilities. The aim of this research program was to develop an analytical model capable of predicting the performance and the strength of GFRP poles. This analytical model had to be verified through extensive experimental work. The first phase of this research program consisted of the experimental investigation. A total of twelve 2.5 m and twelve 6.1 m GFRP poles were tested under lateral loading in accordance with current standards. The specimens were designed to cover a wide range of parameters such as wall thickness, fiber orientation, and fiber arrangement. The experimental results showed that GFRP poles can sustain a transverse load capacity similar to that of wooden, steel or concrete poles with a strength-to-weight ratio considerably higher than these traditional materials. Failure due to local buckling due to flexural was the most dominant failure mode of the specimens tested. The second phase of the research program included an analytical investigation to predict the strength and performance of GFRP poles. The ANSYS finite element program was employed to analyze the tested specimens and to develop a numerical model to analyze GFRP poles. Following the verification of the finite element technique through comparison with the experimental results, a parametric study was conducted to examine the effect of a number of variables including the wall thickness, the fiber orientation and arrangement, and the diameter of GFRP poles. As a result of this parametric study, design charts for various types of poles were developed. Optimum parameter , such as cross section dimensions, wall thickness, and fiber orientation were also developed. In addition to the finite element model and the design charts, a simplified nonlinear analytical model was developed to predict the critical buckling load. This model can also be used to examine the progressive cross-sectional distortion of GFRP poles under steadily increasing loading as well as the occurrence of any local buckling in the section. The laminate stiffness and equivalent moduli used in the analysis were derived from the classical lamination theory. The current study was extended to include the dynamic behavior of GFRP poles by developing a simplified finite element model. Comparison between results from this model and results from the ANSYS finite element program showed an excellent correlation.