Improved Live Load Deflection Criteria for Steel Bridges Final rept

摘要

A literature review was completed to establish the origin and justification for this deflection limit. This review examined numerous papers and reports, and a comprehensive reference list is provided. The work shows that the existing AASHTO deflection limit was initially instituted to control bridge vibration, but deflection limits are not a good method for controlling bridge vibration. Alternate design methods are presented. A survey of state bridge engineers was simultaneously completed to examine how these deflection limits are actually applied in bridge design. The survey also identified bridges that were candidates for further study on this research issue. Candidate bridges either: failed to meet the existing deflection limits; exhibit structural damage that was attributable to excessive bridge deflection; were designed with HPS 70W steel; or had pedestrian or vehicle occupant comfort concerns due to bridge vibration. The survey identified a number of bridges which were experiencing structural damage and reduced service life associated with bridge deflections. Design drawings, inspection reports, photographs, and other information was collected on these bridges. They were grouped and analyzed to: determine whether the damage was truly caused by bridge deflections; determine whether the AASHTO live-load deflection limit played a role in controlling or preventing this damage; and examine alternate methods of controlling or preventing this damage.