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Failure mode analysis of a post-tens...

Corn, Aimee.

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Failure mode analysis of a post-tension anchored dam using linear finite element analysis.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Failure mode analysis of a post-tension anchored dam using linear finite element analysis./
Author:	Corn, Aimee.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2014,
Description:	80 p.
Notes:	Source: Masters Abstracts International, Volume: 76-08.
Contained By:	Masters Abstracts International76-08.
Subject:	Geophysics. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=1573039
ISBN:	9781321490909

Failure mode analysis of a post-tension anchored dam using linear finite element analysis.
Corn, Aimee.

Failure mode analysis of a post-tension anchored dam using linear finite element analysis. - Ann Arbor : ProQuest Dissertations & Theses, 2014 - 80 p.

Source: Masters Abstracts International, Volume: 76-08.

Thesis (M.S.)--Colorado State University, 2014.

There are currently over 84,000 dams in the United States, and the average age of those dams is 52 years. Concrete gravity dams are the second most common dam type, with more than 3,000 in the United States. Current engineering technology and technical understanding of hydrologic and seismic events has resulted in significant increases to the required design loads for most dams; therefore, many older dams do not have adequate safety for extreme loading events. Concrete gravity dams designed and constructed in the early 20th century did not consider uplift pressures beneath the dam, which reduces the effective weight of the structure. One method that has been used to enhance the stability of older concrete gravity dams includes the post-tension anchor (PTA) system. Post-tensioning infers modifying cured concrete and using self-equilibrating elements to increase the weight of the section, which provides added stability. There is a lack of historical evidence regarding the potential failure mechanisms for PTA concrete gravity dams. Of particular interest, is how these systems behave during large seismic events. The objective of this thesis is to develop a method by which the potential failure modes during a seismic event for a PTA dam can be evaluated using the linear elastic finite element method of analysis. The most likely potential failure modes (PFM) for PTA designs are due to tensile failure and shear failure. A numerical model of a hypothetical project was developed to simulate PTAs in the dam. The model was subjected to acceleration time-history motions that simulated the seismic loads. The results were used to evaluate the likelihood of tendon failure due to both tension and shear. The results from the analysis indicated that the PTA load increased during the seismic event; however, the peak load in the tendons was less than the gross ultimate tensile strength (GUTS) and would not be expected to result in tensile failure at the assumed project. The analysis also indicated there was a potential for permanent horizontal displacement along the dam/foundation interface. The horizontal movement was not considered large enough to develop a shear failure of the tendons at the project. The results from this study indicate demand to capacity ratios (DCR) of 0.79 for the anchor head, 0.75 for the tendon, and 0.63 for the foundation cone failure, and a potential displacement of 0.33 inches, which is not large enough to shear the tendon. The methods developed are appropriate for the evaluation of the tensile and shear failure modes for the PTA tendons. Based on the results, it would appear that shear failure of the tendon is a more likely failure mechanism. Thus, shear failure of the tendon should be a focus of seismic evaluations.

ISBN: 9781321490909Subjects--Topical Terms:

535228
Geophysics.
Subjects--Index Terms:

Concrete gravity dam

Failure mode analysis of a post-tension anchored dam using linear finite element analysis.
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245 1 0 $a Failure mode analysis of a post-tension anchored dam using linear finite element analysis.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2014
300 $a 80 p.
500 $a Source: Masters Abstracts International, Volume: 76-08.
500 $a Publisher info.: Dissertation/Thesis.
500 $a Advisor: Heyliger, Paul.
502 $a Thesis (M.S.)--Colorado State University, 2014.
520 $a There are currently over 84,000 dams in the United States, and the average age of those dams is 52 years. Concrete gravity dams are the second most common dam type, with more than 3,000 in the United States. Current engineering technology and technical understanding of hydrologic and seismic events has resulted in significant increases to the required design loads for most dams; therefore, many older dams do not have adequate safety for extreme loading events. Concrete gravity dams designed and constructed in the early 20th century did not consider uplift pressures beneath the dam, which reduces the effective weight of the structure. One method that has been used to enhance the stability of older concrete gravity dams includes the post-tension anchor (PTA) system. Post-tensioning infers modifying cured concrete and using self-equilibrating elements to increase the weight of the section, which provides added stability. There is a lack of historical evidence regarding the potential failure mechanisms for PTA concrete gravity dams. Of particular interest, is how these systems behave during large seismic events. The objective of this thesis is to develop a method by which the potential failure modes during a seismic event for a PTA dam can be evaluated using the linear elastic finite element method of analysis. The most likely potential failure modes (PFM) for PTA designs are due to tensile failure and shear failure. A numerical model of a hypothetical project was developed to simulate PTAs in the dam. The model was subjected to acceleration time-history motions that simulated the seismic loads. The results were used to evaluate the likelihood of tendon failure due to both tension and shear. The results from the analysis indicated that the PTA load increased during the seismic event; however, the peak load in the tendons was less than the gross ultimate tensile strength (GUTS) and would not be expected to result in tensile failure at the assumed project. The analysis also indicated there was a potential for permanent horizontal displacement along the dam/foundation interface. The horizontal movement was not considered large enough to develop a shear failure of the tendons at the project. The results from this study indicate demand to capacity ratios (DCR) of 0.79 for the anchor head, 0.75 for the tendon, and 0.63 for the foundation cone failure, and a potential displacement of 0.33 inches, which is not large enough to shear the tendon. The methods developed are appropriate for the evaluation of the tensile and shear failure modes for the PTA tendons. Based on the results, it would appear that shear failure of the tendon is a more likely failure mechanism. Thus, shear failure of the tendon should be a focus of seismic evaluations.
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650 4 $a Geophysics. $3 535228
650 4 $a Hydrologic sciences. $3 3168407
650 4 $a Civil engineering. $3 860360
653 $a Concrete gravity dam
653 $a Finite element analysis
653 $a Post-tension anchor
653 $a Potential failure mode
653 $a Seismic
690 $a 0373
690 $a 0388
690 $a 0543
690 $a 0467
710 2 $a Colorado State University. $b Civil and Environmental Engineering. $3 2094665
773 0 $t Masters Abstracts International $g 76-08.
790 $a 0053
791 $a M.S.
792 $a 2014
793 $a English
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=1573039