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Effects of Out-of-Plane Patterns on Thin Steel Webs : = Fabrication Imperfections and Low-Frequency Sinusoids.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Effects of Out-of-Plane Patterns on Thin Steel Webs :/
Reminder of title:	Fabrication Imperfections and Low-Frequency Sinusoids.
Author:	Masungi, Parfait Mangwaka.
Description:	1 online resource (297 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-12, Section: B.
Contained By:	Dissertations Abstracts International85-12B.
Subject:	Engineering. -
Online resource:	click for full text (PQDT)
ISBN:	9798382809939

Effects of Out-of-Plane Patterns on Thin Steel Webs : = Fabrication Imperfections and Low-Frequency Sinusoids.
Masungi, Parfait Mangwaka.

Effects of Out-of-Plane Patterns on Thin Steel Webs :Fabrication Imperfections and Low-Frequency Sinusoids. - 1 online resource (297 pages)

Source: Dissertations Abstracts International, Volume: 85-12, Section: B.

Thesis (Ph.D.)--Princeton University, 2024.

Includes bibliographical references

Thin steel plates can resist large shear forces in rolled beams, built-up deep beams (plate girders), and shear walls. When designing large-scale structures, structural engineers can efficiently maximize the shear and flexural resistance of steel plate girders by increasing the depth while minimizing the thickness, which consequently produces more slender webs. However, slender webs are susceptible to a failure phenomenon known as "shear buckling." The objective of this dissertation was to discover and quantify the relationship between out-of-plane patterns on webs of plate girders and the structural strength of plate girders via two specific studies: (1) web out-of-flatness imperfections developed during fabrication, and (2) a type of corrugation in the web plate called "low-frequency sinusoids" (LFS) were examined for both the shear and flexural strength of plate girders. Field measurements, experimental tests, and finite element analyses were the methods employed to meet this objective.During the fabrication stage of welded built-up sections designed with deep webs, not all flat webs remain perfectly straight due to the inevitable effects of rolling, forming, welding, handling, and assembling. The fabrication-induced out-of-flatness patterns on webs are random in size and shape and will impact the shear strength. Various design code specifications in the U.S. and worldwide have provided tolerance limits for fabrication imperfections without any engineering or scientific basis. This dissertation provides qualitative and quantitative data to demonstrate the effects of out-of-flatness imperfections on the shear strength of thin steel webs.The findings of this pioneering research reveal the following:(1) The field measured (as-fabricated) out-of-flatness imperfections do not follow the patterns of the first or second numerical eigenmode and possess larger shear capacity than similar webs examined with eigenmode imperfections. This conclusion is important since all numerical studies to-date use eigenmodes as the initial imperfection, thus leading to appropriately conservative results.(2) Regardless of the initial shape and magnitude of web imperfections, shear buckling in thin webs is a plastic yield mechanism failure penetrating through the web thickness in three stages: elastic stage 1, web mechanism stage 2, and panel mechanism stage 3.(3) The fabrication procedure of LFS plate girders using the roll forming and bump and press forming techniques will increase the shear strength of plate girders by a maximum of 46% above that of flat webs.(4) The elastic lateral-torsional buckling (LTB) strength of LFS plate girders with slender webs as compared to flat webs can increase by up to 9%.Overall, this research leads to important conclusions on the effects of initial imperfections and appropriate methods of their consideration in numerical and experimental studies. The research also enables the development of appropriate fabrication and design specifications for constructing large-scale structures.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798382809939Subjects--Topical Terms:

561152
Engineering.
Subjects--Index Terms:

ImperfectionsIndex Terms--Genre/Form:

554714
Electronic books.

Effects of Out-of-Plane Patterns on Thin Steel Webs : = Fabrication Imperfections and Low-Frequency Sinusoids.
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504 $a Includes bibliographical references
520 $a Thin steel plates can resist large shear forces in rolled beams, built-up deep beams (plate girders), and shear walls. When designing large-scale structures, structural engineers can efficiently maximize the shear and flexural resistance of steel plate girders by increasing the depth while minimizing the thickness, which consequently produces more slender webs. However, slender webs are susceptible to a failure phenomenon known as "shear buckling." The objective of this dissertation was to discover and quantify the relationship between out-of-plane patterns on webs of plate girders and the structural strength of plate girders via two specific studies: (1) web out-of-flatness imperfections developed during fabrication, and (2) a type of corrugation in the web plate called "low-frequency sinusoids" (LFS) were examined for both the shear and flexural strength of plate girders. Field measurements, experimental tests, and finite element analyses were the methods employed to meet this objective.During the fabrication stage of welded built-up sections designed with deep webs, not all flat webs remain perfectly straight due to the inevitable effects of rolling, forming, welding, handling, and assembling. The fabrication-induced out-of-flatness patterns on webs are random in size and shape and will impact the shear strength. Various design code specifications in the U.S. and worldwide have provided tolerance limits for fabrication imperfections without any engineering or scientific basis. This dissertation provides qualitative and quantitative data to demonstrate the effects of out-of-flatness imperfections on the shear strength of thin steel webs.The findings of this pioneering research reveal the following:(1) The field measured (as-fabricated) out-of-flatness imperfections do not follow the patterns of the first or second numerical eigenmode and possess larger shear capacity than similar webs examined with eigenmode imperfections. This conclusion is important since all numerical studies to-date use eigenmodes as the initial imperfection, thus leading to appropriately conservative results.(2) Regardless of the initial shape and magnitude of web imperfections, shear buckling in thin webs is a plastic yield mechanism failure penetrating through the web thickness in three stages: elastic stage 1, web mechanism stage 2, and panel mechanism stage 3.(3) The fabrication procedure of LFS plate girders using the roll forming and bump and press forming techniques will increase the shear strength of plate girders by a maximum of 46% above that of flat webs.(4) The elastic lateral-torsional buckling (LTB) strength of LFS plate girders with slender webs as compared to flat webs can increase by up to 9%.Overall, this research leads to important conclusions on the effects of initial imperfections and appropriate methods of their consideration in numerical and experimental studies. The research also enables the development of appropriate fabrication and design specifications for constructing large-scale structures.
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653 $a Shear mechanism
653 $a Steel web plates
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