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Finite element modeling of non-linear structural response of transmission towers including bolted joint slippage Ahmed, Khaled I. E
Abstract
Slippage of bolted joints plays an important role in the behavior of transmission tower structures under various loading. Two main types of bolted joints are commonly used in towers; column-to-column and beam-to-column joints. The effect of slippage of the bolted joints on the behavior of transmission towers was previously analyzed using two approximate models; instantaneous and continuous joint slippage models. The previously proposed models of joint slippage implied that joint slippage has little effect on a transmission tower load carrying capacity. These models have also shown that deflections of towers due to slippage are very small compared to the overall deformation. These studies have considered on)y beam-to-column joints, ignoring column-to-column joints. The previous models based on the above assumptions and models based on rigid joint behavior were not able to capture the response of transmission towers under considerable differential settlements caused by frost heave. In this thesis, two common bolted joint types used in transmission tower structure are analyzed and discussed based on a series of full-size tower joint experiments conducted at the University of Manitoba. It is observed that joints stiffness properties such as equivalent modulus of elasticity, yield strength and fracture strength are much lower than that of the connected members. The experimental results also show that previously reported instantaneous and continuous joint slippage models do not accurately simulate the behavior of bolted joints. Two finite element models are proposed in this thesis to simulate the slippage of the two main joint types; column-to-column (type-A joints) and beam-to-column (type-C joints). Stiffness matrices of the new joint finite elements are established with the aid of the experimental data. An elastic geometrically nonlinear finite element code is developed using Fortran 90 to analyze the 3-D response of transmission tower structures taking into account the effect of joint slippage. A graphical user interface based on Visual Basic is attached to the finite element code to allow practicing engineers to input all data, build the tower finite element model and display the tower response in an efficient and convenient manner. The response of a 2-D tower substructure and a 3-D full-scale tower used by Manitoba Hydro is analyzed by using the finite element code. The numerical study shows that slippage of beam-to-column and column-to-column joints have significant effects on the tower load carrying capacity. Column-to-column joint slippage shows the most significant impact on the transmission tower behavior by either reducing the tower load carrying capacity or significantly increasing the tower deflection under working loads. On the other hand, joint slippage has a positive effect on the tower response under frost heave induced displacements as substantial redistribution of tower member forces takes place due to joint slippage and actual member forces are much lower than those predicted by standard structural analysis software based on the rigid joint assumption or simplified slippage models.
Item Metadata
Title |
Finite element modeling of non-linear structural response of transmission towers including bolted joint slippage
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2007
|
Description |
Slippage of bolted joints plays an important role in the behavior of transmission tower
structures under various loading. Two main types of bolted joints are commonly used in
towers; column-to-column and beam-to-column joints. The effect of slippage of the bolted
joints on the behavior of transmission towers was previously analyzed using two approximate
models; instantaneous and continuous joint slippage models. The previously proposed models
of joint slippage implied that joint slippage has little effect on a transmission tower load
carrying capacity. These models have also shown that deflections of towers due to slippage
are very small compared to the overall deformation. These studies have considered on)y
beam-to-column joints, ignoring column-to-column joints. The previous models based on the
above assumptions and models based on rigid joint behavior were not able to capture the
response of transmission towers under considerable differential settlements caused by frost
heave.
In this thesis, two common bolted joint types used in transmission tower structure are
analyzed and discussed based on a series of full-size tower joint experiments conducted at the
University of Manitoba. It is observed that joints stiffness properties such as equivalent
modulus of elasticity, yield strength and fracture strength are much lower than that of the
connected members. The experimental results also show that previously reported
instantaneous and continuous joint slippage models do not accurately simulate the behavior of
bolted joints. Two finite element models are proposed in this thesis to simulate the slippage of the two
main joint types; column-to-column (type-A joints) and beam-to-column (type-C joints).
Stiffness matrices of the new joint finite elements are established with the aid of the
experimental data. An elastic geometrically nonlinear finite element code is developed using
Fortran 90 to analyze the 3-D response of transmission tower structures taking into account the
effect of joint slippage. A graphical user interface based on Visual Basic is attached to the
finite element code to allow practicing engineers to input all data, build the tower finite
element model and display the tower response in an efficient and convenient manner.
The response of a 2-D tower substructure and a 3-D full-scale tower used by Manitoba
Hydro is analyzed by using the finite element code. The numerical study shows that slippage
of beam-to-column and column-to-column joints have significant effects on the tower load
carrying capacity. Column-to-column joint slippage shows the most significant impact on the
transmission tower behavior by either reducing the tower load carrying capacity or
significantly increasing the tower deflection under working loads. On the other hand, joint
slippage has a positive effect on the tower response under frost heave induced displacements
as substantial redistribution of tower member forces takes place due to joint slippage and
actual member forces are much lower than those predicted by standard structural analysis
software based on the rigid joint assumption or simplified slippage models.
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Genre | |
Type | |
Language |
eng
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Date Available |
2011-02-18
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0080778
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.