Galvanizing Insights Volume 7, Issue 2

Volume 7, Issue 3

  


An Answer to Bridge Corrosion Concerns

Galvanized Rebar Keeps Bridges Structurally Sound Longer

Though interested parties will have to wait for an official report on the cause of August's Minnesota bridge collapse, no one should wait to specify and construct bridges in a way that is safe, stable, and will last long into the future without fear of structural failure.  Galvanized rebar can strengthen and protect the structural integrity of the bridges that more than four billion vehicles cross each and every day.

Seeping through the porous concrete, corrosive elements can reach the black rebar within a bridge structure and begin the rusting process, creating a corrosive product with a greater volume than the metal consumed in the corrosion reaction. This will cause the internal concrete pressure to build until, eventually, the concrete begins to crack and spall around the corroded rebar, weakening the structure.  According to Constructor magazine, 26 percent of the nation's bridges are structurally deficient; of these, 15 percent are considered deficient because of corroded steel and steel reinforcement issues such as spalling.   > MORE

 



Q: Can I use hot-dip galvanized steel in slip critical connections?

In slip critical connections, all weight bearing surfaces are required to have a slip coefficient greater than 0.30.  Although as-received galvanized bolts and surfaces have a slip factor lower than 0.30, with post-treatment, the slip coefficient of galvanized surfaces increases to meet the requirement.

Some time after the connection is made, galvanized joints develop a characteristic known as "lock-up."  Initially, galvanized surfaces will slip more than black joints.  However, after the first few cycles of applied stress, any slippage will cease and the surfaces will lock-up.  The lock-up is a result of friction between the two galvanized surfaces during dynamic movements.  Therefore, if initial slip is not detrimental to the joint, galvanized steel can be used in the slip critical connection with the same number of bolts as black designs, because over time the galvanized surface will lock-up and provide a slip coefficient equal to black surfaces.  

 

 


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This official publication of the American Galvanizers Association, Inc. (AGA) does not necessarily reflect the view of the board of directors or AGA members. Every effort is made to ensure accuracy. Any errors are strictly accidental and may be corrected in a subsequent issue. This material provides general information only and is not intended as a substitute for competent, professional examination and verification as to suitability and applicability. The publication of the material herein is not intended as a representation or warranty on the part of the AGA. Anyone making use of this information assumes all liability arising from such use. Questions or comments about this publication should be directed to the AGA. Comments and suggestions are encouraged.

Copyright © 2007 American Galvanizers Association. The material provided herein has been developed to provide accurate and authoritative information about after-fabrication hot-dip galvanized steel. This material provides general information only and is not intended as a substitute for competent professional examination and verification as to suitability and applicability. The information provided herein is not intended as a representation or warranty on the part of the AGA. Anyone making use of this information assumes all liability arising from such use.