M.Ing. / The purpose of this investigation was to develop a double concrete pole which could be used as an angle- or terminal structure for overhead power lines. To act as a double pole, shear flow must be transferred effectively between the two single poles to create the new stronger section. The method to transfer the shear flow must also be practical and economical...

Submitted as the dissertation component in partial fulfillment of the requirements for the Masters Diploma in Technology (Electrical engineering - heavy current), Electrical Engineering, ML Sultan Technikon, 1998. / The use of pre-stressed concrete poles for the Inwabi Plateau rural distribution line has presented unforseen problems for the Durban Electricity Service Unit, such as poor line performance and structural damage to the poles. The effects are thought to be due to lightning. This dissertation deals with an investigation into the cause of the damage as well as recommendations regarding the repair and prevention of future damage. To achieve this, an evaluation of the line Basic Insulation Level (B.I.L.) together with a review of the existing literature on the effects of lightning to overhead lines was used in order to establish what the specific damage mechanisms are. Field and laboratory tests were also undertaken as part of the investigation. Based on the results obtained, the overhead line was modified in terms of it's B.I.L. A preliminary evaluation of the modifications was done, with recommendations regarding further work to be done in the future. / M

Reinforced concrete poles are commonly used as street lighting and electrical transmission poles. Typical concrete lighting poles experience very little load due to torsion. The governing design loads are typically bending moments as a result of wind on the arms, fixtures, and the pole itself. The Canadian pole standard, CSA A14-07 relates the helical reinforcing to the torsion capacity of concrete poles. This issue and the spacing of the helical reinforcing elements are investigated. Based on the ultimate transverse loading classification system in the Canadian standard, the code provides a table with empirically derived minimum helical reinforcing amounts that vary depending on: 1) the pole class and 2) distance from the tip of the pole. Research into the minimum helical reinforcing requirements in the Canadian code has determined that the values were chosen empirically based on manufacturer’s testing. The CSA standard recommends two methods for the placement of the helical reinforcing: either all the required helical reinforcing is wound in one direction or an overlapping system is used where half of the required reinforcing is wound in each direction. From a production standpoint, the process of placing and tying this helical steel is time consuming and an improved method of reinforcement is desirable. Whether the double helix method of placement produces stronger poles in torsion than the single helix method is unknown. The objectives of the research are to analyze the Canadian code (CSA A14-07) requirements for minimum helical reinforcement and determine if the Canadian requirements are adequate. The helical reinforcement spacing requirements and the effect of spacing and direction of the helical reinforcing on the torsional capacity of a pole is also analyzed. Double helix and single helix reinforcement methods are compared to determine if there is a difference between the two methods of reinforcement. The Canadian pole standard (CSA A14-07) is analyzed and compared to the American and German standards. It was determined that the complex Canadian code provides more conservative spacing requirements than the American and German codes however the spacing requirements are based on empirical results alone. The rationale behind the Canadian code requirements is unknown. A testing program was developed to analyze the spacing requirements in the CSA A14-07 code. Fourteen specimens were produced with different helical reinforcing amounts: no reinforcement, single and double helical spaced CSA A14-07 designed reinforcement, and single helical specimens with twice the designed spacing values. Two specimens were produced based on the single helical reinforcement spacing. One specimen was produced with helical reinforcement wound in the clockwise direction and another with helical reinforcement in the counter clockwise direction. All specimens were tested under a counter clockwise torsional load. The clockwise specimens demonstrated the response of prestressed concrete poles with effective helical reinforcement whereas the counter clockwise reinforced specimens represented theoretically ineffective reinforcement. Two tip sizes were produced and tested: 165 mm and 210 mm. A sudden, brittle failure was noted for all specimens tested. The helical reinforcement provided no post-cracking ductility. It was determined that the spacing and direction of the helical reinforcement had little effect on the torsional capacity of the pole. Variable and scattered test results were observed. Predictions of the cracking torque based on the ACI 318-05, CSA A23.3-04 and Eurocode 2 all proved to be unconservative. Strut and tie modelling of the prestressing transfer zone suggested that the spacing of the helical steel be 40 mm for the 165 mm specimens and 53 mm for the 210 mm specimens. Based on the results of the strut and tie modelling, it is likely that the variability and scatter in the test results is due to pre-cracking of the specimens. All the 165 mm specimens and the large spaced 210 mm specimens were inadequately reinforced in the transfer zone. The degree of pre-cracking in the specimen likely causes the torsional capacity of the pole to vary. The strut and tie model results suggest that the requirements of the Canadian code can be simplified and rationalized. Similar to the American spacing requirements of 25 mm in the prestressing transfer zone, a spacing of 30 mm to 50 mm is recommended dependent on the pole tip size. Proper concrete mixes, adequate concrete strengths, prestressing levels, and wall thickness should be emphasized in the torsional CSA A14-07 design requirements since all have a large impact on the torsional capacity of prestressed concrete poles. Recommendations and future work are suggested to conclusively determine if direction and spacing have an effect on torsional capacity or to determine the factors causing the scatter in the results. The performance of prestressed concrete poles reinforced using the suggestions presented should also be further investigated. Improving the ability to predict the cracking torque based on the codes or reducing the scatter in the test results should also be studied.

Reinforced concrete poles are commonly used as street lighting and electrical transmission poles. Typical concrete lighting poles experience very little load due to torsion. The governing design loads are typically bending moments as a result of wind on the arms, fixtures, and the pole itself. The Canadian pole standard, CSA A14-07 relates the helical reinforcing to the torsion capacity of concrete poles. This issue and the spacing of the helical reinforcing elements are investigated. Based on the ultimate transverse loading classification system in the Canadian standard, the code provides a table with empirically derived minimum helical reinforcing amounts that vary depending on: 1) the pole class and 2) distance from the tip of the pole. Research into the minimum helical reinforcing requirements in the Canadian code has determined that the values were chosen empirically based on manufacturer’s testing. The CSA standard recommends two methods for the placement of the helical reinforcing: either all the required helical reinforcing is wound in one direction or an overlapping system is used where half of the required reinforcing is wound in each direction. From a production standpoint, the process of placing and tying this helical steel is time consuming and an improved method of reinforcement is desirable. Whether the double helix method of placement produces stronger poles in torsion than the single helix method is unknown. The objectives of the research are to analyze the Canadian code (CSA A14-07) requirements for minimum helical reinforcement and determine if the Canadian requirements are adequate. The helical reinforcement spacing requirements and the effect of spacing and direction of the helical reinforcing on the torsional capacity of a pole is also analyzed. Double helix and single helix reinforcement methods are compared to determine if there is a difference between the two methods of reinforcement. The Canadian pole standard (CSA A14-07) is analyzed and compared to the American and German standards. It was determined that the complex Canadian code provides more conservative spacing requirements than the American and German codes however the spacing requirements are based on empirical results alone. The rationale behind the Canadian code requirements is unknown. A testing program was developed to analyze the spacing requirements in the CSA A14-07 code. Fourteen specimens were produced with different helical reinforcing amounts: no reinforcement, single and double helical spaced CSA A14-07 designed reinforcement, and single helical specimens with twice the designed spacing values. Two specimens were produced based on the single helical reinforcement spacing. One specimen was produced with helical reinforcement wound in the clockwise direction and another with helical reinforcement in the counter clockwise direction. All specimens were tested under a counter clockwise torsional load. The clockwise specimens demonstrated the response of prestressed concrete poles with effective helical reinforcement whereas the counter clockwise reinforced specimens represented theoretically ineffective reinforcement. Two tip sizes were produced and tested: 165 mm and 210 mm. A sudden, brittle failure was noted for all specimens tested. The helical reinforcement provided no post-cracking ductility. It was determined that the spacing and direction of the helical reinforcement had little effect on the torsional capacity of the pole. Variable and scattered test results were observed. Predictions of the cracking torque based on the ACI 318-05, CSA A23.3-04 and Eurocode 2 all proved to be unconservative. Strut and tie modelling of the prestressing transfer zone suggested that the spacing of the helical steel be 40 mm for the 165 mm specimens and 53 mm for the 210 mm specimens. Based on the results of the strut and tie modelling, it is likely that the variability and scatter in the test results is due to pre-cracking of the specimens. All the 165 mm specimens and the large spaced 210 mm specimens were inadequately reinforced in the transfer zone. The degree of pre-cracking in the specimen likely causes the torsional capacity of the pole to vary. The strut and tie model results suggest that the requirements of the Canadian code can be simplified and rationalized. Similar to the American spacing requirements of 25 mm in the prestressing transfer zone, a spacing of 30 mm to 50 mm is recommended dependent on the pole tip size. Proper concrete mixes, adequate concrete strengths, prestressing levels, and wall thickness should be emphasized in the torsional CSA A14-07 design requirements since all have a large impact on the torsional capacity of prestressed concrete poles. Recommendations and future work are suggested to conclusively determine if direction and spacing have an effect on torsional capacity or to determine the factors causing the scatter in the results. The performance of prestressed concrete poles reinforced using the suggestions presented should also be further investigated. Improving the ability to predict the cracking torque based on the codes or reducing the scatter in the test results should also be studied.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Title from PDF title page (viewed Feb. 5, 2010). Additional advisors: Ashraf Al Hamdan, Wilbur A. Hitchcock, Jason T. Kirby, Talat Salama. Includes bibliographical references (p. 148-153).

Historic concrete fence posts were created in the early twentieth century. This study examined how they were constructed and who constructed them. A survey of Randolph county, Indiana was conducted in order to determine the possible construction methods. Literature sources indicate that farmers were encouraged to construct concrete posts on their own. The survey also points to the idea that historic concrete fence posts were created by the farmers who used them. While commercially manufactured posts exist in Randolph county, they are from a later date, and thus not the focus of this study. Interviews with members off the farming community also indicate that most farmers built their own concrete fence posts, from molds they also made. While many businesses and colleges promoted the use and construction of concrete fence posts, they were individually made to serve farmers' immediate and long term fencing needs. / Department of Architecture

Poles are used as an important constituent of transmission, distribution and communication structures / highway and street lighting systems and other various structural applications. Concrete is the main production material of the pole industry. Concrete is preferred to steel and wood due not only to environmental and economic reasons but also because of its high durability to environmental effects and relatively less frequent maintenance requirements. Centrifugal casting is the most preferred way of manufacturing concrete poles. However, misapplication of the method may lead to a significant reduction in strength and durability of the poles. Segregation of concrete mixture is a frequent problem of centrifugal casting. The segregated concrete within the pole cross-section possesses different physical properties. In particular, the shrinkage tendency of the inner concrete, where the cement paste is accumulated, becomes significantly larger. Differential shrinkage of hardened concrete across the pole section gives rise to the development of internal tensile stresses, which, in turn, results in longitudinal cracking along the poles. There is a vast literature on experimental studies of parameters affecting differential shrinkage of centrifugally cast poles. This research aims to computationally investigate the differential shrinkage-induced internal stress development and cracking of concrete poles. To this end, two and three-dimensional mathematical models of the poles are constructed and finite element analyses of these models are carried out for different scenarios. The computationally obtained results that favorably agree with the existing experimental data open the possibility to improve the centrifugal manufacturing technique by using computational tools.