Title page for ETD etd-10122011-150234

Type of Document

Master's Thesis

Author

Passarelli, Garrett J

Author's Email Address

passarg@vt.ed

URN

etd-10122011-150234

Title

A Feasiblity Study on the Fatigue Performance of Laser Beam Welds and Hybrid-Laser Arc Welds Used in an Innovative Modular Steel Sandwich Panel Bridge Deck SyStem

Degree

Master of Science

Department

Civil Engineering

Advisory Committee

Advisor Name	Title
Wright, William J.	Committee Chair
Moen, Cristopher D.	Committee Co-Chair
Cousins, Thomas E.	Committee Member

Keywords

Bridge Decks
Fatigue Resistance
Finite Element Analysis
Finite Element
Sandwich Panel
Laser Weld
LBW
HLAW

Date of Defense

2011-09-28

Availability

restricted

Abstract

This research investigation explores the feasibility of implementing a laser welded
sandwich steel panel bridge deck system as a viable alternative to standardized reinforced
concrete bridge decks. Generally used in naval ship building applications, steel sandwich
panels possess attractive characteristics towards the integration with bridge infrastructure such
as service life in excess of 100 plus years, dead load reduction, rapid construction, decreased
closure time, and automated mass production. The lack of fatigue data for the laser “stake”
welds used to create the enclosed sandwich panel geometry raised concerns with respect to
fatigue life. The primary focus of this study was to determine whether or not infinite fatigue life
was possible. Two different laser welding technologies were investigated, Laser Beam
Welding (LBW) and Hybrid-Laser Arc Welding (HLAW). Test specimens were fabricated and
tested in order to examine fatigue resistance based on a localized load effect between adjacent
core stiffeners. Finite element models were used to obtain the stress range for each individual
test due to complex geometry and partially restrained boundary conditions. In order to assess
the fatigue performance of the overall deck system, additional finite element models were
created to study the local and global behavior of different sandwich panel configurations. As a
whole the investigation yielded promising results. Infinite fatigue life is achievable due to
outstanding fatigue performance. The HLAW stake welds demonstrated superior fatigue
resistance in comparison to the LBW process. Localized load effects can be minimized
through the modification of different panel parameters. Pushing forward, full scale testing is
essential to the future employment of this innovative bridge deck system.

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