بررسي تاثير زبري هاي موضعي در كنترل و كاهش آب شكستگي موضعي تك پل ها

چكيده انگليسي :

100 Investion of roughness effect on reduction of local scour bridge piers Amir Bahrami Amir ba hra mi 67@ ya hoo co m June 21 2015 Departement of Water Engineering College of Agriculture Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Manouchehr Heidarpour heidar@cc iut irAbstractBridges are structures in danger of destruction due to being subjected to flood river bed Local scour around piersacross the flood flow is one of the threatening factors of their stability Water stream cause digging hole aroundpier and leaching river bed that consequently may result in hollowing under the foundation and finally destroyingthe bridge Many studies have been done presenting methods for controlling scour around piers Generally there aretwo base methods for protection of bridges against scour phenomenon that first one is increasing resistance of bedmaterials and second is decreasing erosion factors In direct methods riprap and cement blocks are used toincrease bed resistance Riprap collar pile are the tools that use for decreasing downward scour and horse shoevortex in indirect methods Using piers with concrete roughness is one of the economical methods easy to implement Considering the results of cable method the lower the twisting angle of cable the higher efficiency of pier in reducingscour can be obtained Ability of reducing concrete roughness angle to zero degree is counting as an advantageof this method compared to cable method Another advantage of concrete roughness than cable is their inabilityof displacement by human factors In this study effect of concrete roughness in decreasing scour factors isinvestigated For achieving this goal 17 piers with different roughnesses in two base states with presence ofangular and rounded roughnesses are used Experiments of angular roughnesses are done by 11 piers with constantroughness width of 0 06 of diameter Increasing in protrusions leads to increasing in their performance However in particular conditions that distance between roughnesses is less than optimum value increas e in width of pier is afactor to decrease the efficiency of roughnesses Performance of pier has a direct relation with protrusions ofroughnesses and effective area across the downward stream path with respect to increase in width of pier restriction Performance of pier in reducing scour is increased and length and width of final digged hole are decreased asprotrusion of roughnesses is increased Designed diagram and equations that are presented in this study can beused for selecting optimum distance between roughnesses In con stant C D 0 06 and protrusions of 0 06 and 0 07of pier diameter optimum distance of roughnesses is estimated to be 0 51 of pier diameter Best performance inpresence of angular pier and protrusion 0 07of pier diameter is about 34 Finally it seems that for every roughnesswith particular protrusion there is an optimum value for distance between roughnesses Experiments of pier withpresence of rounded roughnesses are done with this consideration that in long periods angular roughnesses areturned to rounded roughnesses These experiments in addition to representing another form of roughnesses areproofs to performance of angular roughnesses in long periods For this goal large diameter of semi ellipse and smallradius of semi ellipse is considered to be less than 0 11 and 0 06 respectively Thus with considering distancesbetween roughnesses 22 improvement in performance for increasing scour can be achieved With reducingnumber of roughnesses it could be seen that presence of roughnesses in all of piers is not necessary Consequentlyconsidering effectiveness of roughnesses in scour factors their location has a particular range Keywords scour pier scour control concrete roughness

بهرامي، امير

بررسي تاثير زبري هاي موضعي در كنترل و كاهش آب شكستگي موضعي تك پل ها

پايه پل , زبري بتني