The Earthquake Engineering Online Archive

Fatigue life evaluation of changeable message sign structures -- Volume 1: As-built specimens

Gilani, Amir S.; Chavez, Juan W.; Whittaker, Andrew S.

UCB/EERC-97/10, Earthquake Engineering Research Center, University of California, Berkeley, 1997-11, 181 pages (645/G54/1997)

Changeable message sign structures (CMSs) are inverted "L" shape structures, fabricated from steel pipe sections and composed of a vertical (post) section that is connected to a horizontal (mast arm) section by a flanged connection. The sign structures are inherently flexible and have low structural damping. Following the failure of one CMS structure in Southern California, field studies were undertaken that indicated that the groove-welded mast arm (post)-flange plate and post-base plate connections are susceptible to wind-induced fatigue cracking. Caltrans then identified seven topics for urgent study. This report addresses four of these topics: evaluation of the fatigue life of as-built connection details; assessment of the stress increase in CMS components adjacent to the conduit holes; estimation of the dynamic characteristics of CMS structures; and preparation of draft recommendations for improving the fatigue life of as-built CMS structures. To investigate the fatigue life of as-built CMS structures, laboratory tests of three mast arms and one cantilever post were undertaken. A mathematical (finite element) model of the CMS structure was developed, and available field data was analyzed. Recommendations are given.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-97-10.pdf (42 MB)