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<br />I <br />I <br /> <br />, <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I' <br />I <br /> <br />o <br /> <br />Technical Advisory <br /> <br />us. Oa,...w Ill.. If <br />a la....... lClIiCn <br />'ldaraltlghway <br />Adn....II...I~ <br /> <br />Subject <br /> <br />!;COUll. AT BRIDGES <br /> <br />C1aasitiClllton Code <br />T 5140.20 CHG.l <br /> <br />Dale <br />November 7, 1988 <br /> <br />1. <br /> <br />PURPOSE. To modify the equation for sizing riprap at piers in the <br />Attachment to Technical Advisory T 5140.20 entitled, "Interim <br />Procedures for Evaluating Scour at Bridges." <br /> <br />2. <br /> <br />CANCELLATION. Page 61 of the Attachment to Technical Mvisory <br />T 5140.20 is cancelled. <br /> <br />EXPLANATION OF CHANGE. Modification of the equation for sizing <br />riprap at piers (page 61 of the Attachment) is necessary since the <br />equation overestimates the required riprap size. This change <br />reduces the coefficient in the equation from 1.384 to 0.692. <br /> <br />3. <br /> <br />d.dJ~ <br /> <br />Thomas O. Willett, Director <br />Office of Engineering <br /> <br />FILING INSTRUCTIONS <br /> <br />Pa<:\e Changes <br />Remove <br /> <br />Insert <br /> <br />61 and 62 of FHWA <br />Technical Advisory <br />T 5140.20 dated 09/16/88 <br /> <br />61 and 62 of FHWA <br />Technical Advisory T 5140.20 <br /> <br />DISTRIBUTION: Level 2: Headquarters (NR,RT ,HI ,DF ,HO,HS) <br />Regions (S!) <br />Divisions (BR) <br />All Direct Federal Div. <br />Level 3: SHA's(Through Divisions) <br /> <br />OPt HNG-3l <br />