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No description available.

Large diameter concrete pipes have been used in many areas of central Florida to carry pressured sewage flow. These pipes have been typically located at six feet below finished roadway elevation, and ranges in diameter from thirty six to sixty inches. The water table is typically located at shallow depth below finished roadway elevation, and generally fluctuates between five to ten feet depending on the relative roadway elevation to mean sea level. These pipes are under pressure when carrying the sewage flow, but return to normal atmospheric pressures when the flow stops. Since the water table encases most of the pipe circumference, no leaks is developed from the water table to the pipe when the pipe is under pressure. Once the pressure in the pipes returns to zero, the water starts seeping into the pipe while washing the subgrade with it into the pipe's interior. The subgrade washes into the pipe at the joint inverts between adjacent pieces of the pipe, since the invert is where the most tension exists in the joint under the weight of the soil and traffic loading above the pipe, making it the most probable location where a gap in the joint would form. This would cause the origination of a small void under the pipe, which creates pressure redistribution in the subgrade reaction under the pipe. As the void develops in the middle third of the bedding under the invert, pressure redistribution occurs to the outer two thirds of the bedding. As the stress increases in the outer portions of the bedding, more subgrade material is washed into the pipe when it is not under pressure, making the void larger. As the void becomes large, the moment in the pipe is greatly increased, and therefore the gap in the joint is increased due to the tension increase at the bottom of the pipe. More material is allowed into the pipe, and the void becomes deeper as fewer restrictions are encountered between the water table and the empty pipe. As the pipe becomes pressurized, more subgrade material is disturbed by the leak from the inside of the pipe to the outside, and void is constantly generated. The void then leads to the continuous settlement of the roadway. It is intended by this study to model the stresses in the subgrade around the pipe using a finite element software to determine the effects of void in the pipe's bedding on the stress around the pipe's outer perimeter. The stresses calculated as a result of the void will then be used in determining the increase in internal moment created in the pipe as the void is generated and became larger and deeper. Average stresses on the top and bottom of the pipe were calculated due to the soil profile dead load and live load caused by loading the soil profile with one and two HS-20 trucks. The average stresses were recalculated after the addition of void in the pipe bedding. The void width and depth were varied to come up with the case that would generate the highest unbalanced load on the pipe. The average bottom stress was subtracted from the average top stress to determine the unbalanced load on the pipe that would cause an internal moment in the pipe. At the most critical case, a forty kilo pounds per foot moment was caused by the existence of the void under the sixty inch diameter pipe used in the model. Such a moment is large to be resisted by either the pipe alone or the pipe reinforced by an additional structural support, unless such support is accompanied by void decrease and a mean to stop the subgrade from eroding into the pipe.

As vast networks of high pressure buried energy pipelines traverse North America and other continents, the stability of such essential buried infrastructure must be maintained under a variety of earth loading conditions. The pipe-soil interaction and the longitudinal behaviour of buried pipes due to relative ground movements is poorly understood. This thesis presents full scale testing and numerical modeling of steel and Glass Fibre Reinforced Polymer (GFRP) pipelines to better understand the flexural performance of buried pipes subjected to lateral earth movement. For the experimental phase of the study, a series of pipe bending experiments have been conducted on 102 mm nominal diameter and 1830 mm long steel and GFRP pipes buried in dense sand. Pipe loading was carried out by pulling pipe ends using two parallel cables attached to a spreader beam outside the test region, using a hydraulic actuator. The different tests covered burial depth-to-diameter (H/D) ratios of 3, 5 and 7. During the steel pipe testing phase, special consideration was given to assess the effect of boundary limits, friction within the pulling mechanism, and consistency of results using repeated tests. For the GFRP pipes, the experimental work investigated the effect of the laminate structure of the pipes, including both cross-ply and angle-ply laminates. Test results showed that burial depth significantly influenced the ultimate pulling forces, longitudinal strains, and pipe net deflection at mid-span. The results were also compared between the two types of pipes. The failure mechanism for all tests was consistently governed by soil failure, except for the angle-ply GFRP pipe that failed at a burial depth of H/D=7. For the numerical analysis, the study presents the development and verification of two and three-dimensional numerical models including material constitutive models for both the pipe and for the soil using a stress-dependent modulus. Calculations are presented for different burial depths and are compared to experimental data. It was shown that the numerical model can successfully capture the pipe-soil interaction behaviour for both pipe types in terms of load-displacement responses and net bending deflection. Also, the effect of material variation and laminate structure were in agreement with test data. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2013-04-18 22:21:53.025

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A new method of connecting cross-frames to bridge girders had been proposed to alleviate concerns with current design practices. This new, half-pipe detail needs to be examined for fatigue issues that may exist which would make it infeasible as a replacement candidate for the current bent-plate design. A program of laboratory testing was carried out to determine the comparative performance between the half-pipe and the bent-plate designs. These tests were then translated into a finite element model which was examined to determine behavior over a wide range of designs scenarios. Finite element results, along with the laboratory testing data, were used to determine the appropriate use of the half-pipe stiffener. / text

One of the requirements of a safe nuclear power plant design is the postulation of the dynamic effects of a steam pipe rupture. The dynamic effects are the discharging fluid and pipe whip on structures, systems or components. A pipe rupture can be caused in the steam pipe system where a defect such as a crack exists. Multiple factors contribute to the initiation of pipe cracks during the plant’s life. Cracks may start microscopically small and over time, with the assistance of cyclic operation, fatigue may elongate the crack. When a steam pipe is cooled by water during an accident, steam condensate may accumulate and form slugs of water. This water will have an effect on the system termed condensation induced water hammer. The cause of the pipe rupture is not addressed in this dissertation. Pipe rupture can be considered to be either a circumferential or longitudinal break. For the purpose of this dissertation only a circumferential break will be considered. This research is based on the development of a pipe whip restraint structure to protect the plant environment during a steam pipe rupture event in a nuclear power plant. It focuses on a structural component required to restrain the dynamic energy to an acceptable level. Whip restraints used in the nuclear industry are typically honeycomb, U-bar and crush pipe types. In this dissertation only the U-bar and crush pipe whip restraints will be considered. The plant environment, with regards to pipe layout, plays a large role in determining the type of restraint to be used, whether it is U-bar or crush pipe. A whip towards the wall/structure will favor a crush pipe; a whip away from the wall/structure will favor a U-bar restraint. In this project the crush pipe is selected where the whip is towards a wall/structure. The crush pipe also represents a simpler design. First-order analysis is performed using the energy method to determine the conceptual geometry of the whipping component and the restraint geometry. Second-order analysis includes finite element analysis to verify the first-order results. In this dissertation the concept validation is done using LS-PrePost. for the pre- and post-processing while the analysis is performed using LS-DYNA ®. During the second-order analysis it was demonstrated that the energy is successfully absorbed by the crush pipe and thus the first-order analysis is considered adequate. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

One of the requirements of a safe nuclear power plant design is the postulation of the dynamic effects of a steam pipe rupture. The dynamic effects are the discharging fluid and pipe whip on structures, systems or components. A pipe rupture can be caused in the steam pipe system where a defect such as a crack exists. Multiple factors contribute to the initiation of pipe cracks during the plant’s life. Cracks may start microscopically small and over time, with the assistance of cyclic operation, fatigue may elongate the crack. When a steam pipe is cooled by water during an accident, steam condensate may accumulate and form slugs of water. This water will have an effect on the system termed condensation induced water hammer. The cause of the pipe rupture is not addressed in this dissertation. Pipe rupture can be considered to be either a circumferential or longitudinal break. For the purpose of this dissertation only a circumferential break will be considered. This research is based on the development of a pipe whip restraint structure to protect the plant environment during a steam pipe rupture event in a nuclear power plant. It focuses on a structural component required to restrain the dynamic energy to an acceptable level. Whip restraints used in the nuclear industry are typically honeycomb, U-bar and crush pipe types. In this dissertation only the U-bar and crush pipe whip restraints will be considered. The plant environment, with regards to pipe layout, plays a large role in determining the type of restraint to be used, whether it is U-bar or crush pipe. A whip towards the wall/structure will favor a crush pipe; a whip away from the wall/structure will favor a U-bar restraint. In this project the crush pipe is selected where the whip is towards a wall/structure. The crush pipe also represents a simpler design. First-order analysis is performed using the energy method to determine the conceptual geometry of the whipping component and the restraint geometry. Second-order analysis includes finite element analysis to verify the first-order results. In this dissertation the concept validation is done using LS-PrePost. for the pre- and post-processing while the analysis is performed using LS-DYNA ®. During the second-order analysis it was demonstrated that the energy is successfully absorbed by the crush pipe and thus the first-order analysis is considered adequate. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

Thesis (Doctoral Engineering)--Norwegian Institute of Technology, 1992. / Includes bibliographical references (p. 8.1-8.9).

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains x, 122 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 116-122).