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<br /> -- <br /> Local Pier Scour Depths Based on Mode" <br /> Angle of Vel Adjusted <br />Run Test Prototype <br />No. Condition Attack Modeled Scour <br /> (degrees) (ftIs) (ft) <br /> - <br />10 No web wall 15 4.81 6.42 <br /> - <br /> Multiple columns 15 <br /> - <br />11 No web wall 26 4.82 6.23 <br /> Multiple columns 26 <br />3 Web wall at bed 15 4.97 7.08 <br />2 Web wall at bed 26 4.63 8.93 <br /> - <br />9 Web wall above bed 15 4.86 6,67 <br /> - <br />1 Web wall above bed 26 4,73 6,75 <br /> - <br />~EC~18 recommends multiplying single column dep~h by 1.2 when multiple (:~I <br /> <br />B. Conclusions from model study. <br /> <br />and HEC-18 Re <br /> <br /> Pier <br /> rdth, a L <br /> (ft) <br />- <br /> 1.5 <br />- <br /> 1.5 <br /> 1.5 <br /> 1.5 <br />- <br />- <br />- <br />- <br /> <br />Pier <br />Wi ength, <br />(ft) <br /> <br />umns are spaced 5 dia <br /> <br />1,5 <br />9.0 <br /> <br />suits. <br /> HEc-18 <br />L K, Predicted <br />Scour <br /> (ft) <br /> 1.2* 6.3 <br /> 1.8 9.5 <br /> 1.2* 6.4 <br /> 2.3 12.2 <br />-. <br /> NA <br /> NA <br /> NA <br /> NA <br />meters or greater apart. <br /> <br />1.5 <br /> <br />9,0 <br /> <br />1. Local scour on piers was about 2.04 m (6.'7 feet) (Runs 1 and 9) <br />because web wall would have been above the bed as a result of <br />contraction scour. <br /> <br />2. HEC-18 pier scour equation gives good results except for the case <br />of the web wall E~xtending into the bed. <br /> <br />Long term degradation -. 3.0 m <br />Contraction scour -- 2.6 m <br />Pier scour _. 2.0 m <br />Total -. 7.6 m <br /> <br />C. Conclusions from 1-5 bridge failure <br /> <br />1. Total scour depth. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />2. Column embedment remaining. <br /> <br />12.5 - 7,Ei = 4,9 m <br /> <br />(10.0 feet) <br />( 8.5 feet) <br />L 6.7 feetl <br />(25,2 feet) <br /> <br />(4'10 - 25,2 = 15.8 feet) <br /> <br />5.13 <br />