Lessons in bridge damage learned from the Wenchuan earthquake

A strong earthquake occurred in Wenchuan County,Sichuan Province,China,on May 12,2008.Shortly after the earthquake,the Turner-Fairbank Highway Research Center of the Federal Highway Administration,in partnership with the Research Institute of Highways,the Ministry of Communication of China,led a reconnaissance team to conduct a post-earthquake bridge performance investigation of the transportation system in the earthquake affected areas.The U.S.transportation system reconnaissance team visited the area during July 20-24,2008.This paper presents the fi ndings and lessons learned by the team.

Bridge Pressure Flow Scour at Clear Water Threshold Condition

Bridge pressure flow scour at clear water threshold condition is studied theoretically and experimentally.The flume experiments reveal that the measured scour profiles under a bridge are more or less 2-dimensional;all the measured scour profiles can be described by two similarity equations,where the horizontal distance is scaled by the deck width while the local scour by the maximum scour depth;the maximum scour position is located just under the bridge about 15% deck width from the downstream deck edge;the scour begins at about one deck width upstream the bridge while the deposition occurs at about 2.5 deck widths downstream the bridge;and the maximum scour depth decreases with increas-ing sediment size,but increases with deck inundation.The theoretical analysis shows that:bridge scour can be divided into three cases,i.e.downstream unsubmerged,partially submerged,and totally submerged.For downstream unsubmerged flows,the maximum bridge scour depth is an open-channel problem where the conventional methods in terms of critical velocity or bed shear stress can be applied;for partially and totally submerged flows,the equilibrium maximum scour depth can be described by a scour and an inundation similarity number,which has been confirmed by experiments with two decks and two sediment sizes.For application,a design and field evaluation procedure with examples is presented,including the maximum scour depth and scour profile.

Caltrans use of scrap tires in asphalt rubber products:a comprehensive review

The California Department of Transportation(Caltrans) has been using scrap tire rubber in asphalt pavements since the 1970 s in chip seals and the 1980 s in rubberized hot mix asphalt(RHMA).Both the wet(field blend) and dry processes were used in early trials.Caltrans has also used rubber modified binders containing both crumb rubber modifier and polymer modifier that could be manufactured at a refinery facility,a terminal blend wet process.Since the beginning of this century,Caltrans increased the use of scrap tire rubber in paving projects and invested considerable resources in developing technically sound,cost effective,and environmentally friendly strategies for using scrap tire rubber in roadway applications.By the end of year 2010,approximately 31%of all hot mix asphalt(HMA) placed by Caltrans was rubberized HMA,roughly 1.2 million tons.Caltrans efforts in using asphalt rubber products were also demonstrated in its research and technology development.These included the construction of two full-scale field experiments,five warranty projects,and an accelerated pavement study using a heavy vehicle simulator.Additionally,terminal blend asphalt rubber and rubberized warm mix asphalts began to be experimented on trial basis.This paper provides a comprehensive review of Caltrans experience over four decades with asphalt rubber products.Current practices and future outlook are also discussed.