Title:	Lehigh Khan Lecture Series - “Overcoming Barriers to Durable Steel Bridge Systems"
Date:	Apr. 18, 2008
Locations:	Bethelehem, PA, USA
Details:	Experience with steel bridges has demonstrated that one of the primary barriers to durability was inadequacies in the fatigue design criteria and practice prior to 1974. The development of a rational fatigue resistance knowledge base and the introduction of stress range as the appropriate fatigue design criteria minimized this limitation. Small web gaps and arbitrary rules to avoid welding to tension flanges resulted in extensive web gap fatigue cracking from out-of-plane distortion. Small web gaps can also result in tri-axiality resulting in brittle fracture. Improvements of existing details by end weld treatment using peening and gas tungsten arc remelting are examined as procedures to enhance the fatigue resistance of existing structures. Experience with these procedures since the 1970’s is reviewed. More recent work on Ultrasonic Impact Treatment (UIT) together with the need for end weld design changes are shown to effectively eliminate fatigue as controlling design. For the future, High Performance Steels (HPS) are providing enhanced weathering resistance for uncoated members along with more reliable fracture resistance and weldability. Control of water and debris by minimizing joints in bridge decks offers enhanced protection for both coated and uncoated bridge members. The orthotropic steel deck is shown to be a system providing modularity for prefabrication and easy erection. This system is capable of providing a 100 year life when thicker deck plates are used with thin epoxy concrete wearing surfaces. These have been shown to permit immediate use and are not pot hole sensitive even if local surface deterioration develops. Location: Sinclair Lab Auditorium, Lehigh University, 7 Asa Drive, Bethlehem, PA, USA. For more information go to: http://www.lehigh.edu/frkseries Please contact Leslie Ladick at 610.758.6123 or ljl2@lehigh.edu