EFFECT OF DIFFERENT SHAPES OF BRIDGE PIERS TO MINIMIZE LOCAL SCOUR

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 1, January 2018, pp , rticle ID: IJCIET_09_01_061 vailable online at ISSN Print: and ISSN Online: IEME Publication Scopus Indexed EFFECT OF DIFFERENT SHPES OF RIDGE PIERS TO MINIMIZE LOCL SCOUR Kamini hagwat Funde P.G.Student, Civil Engineering Department, harati Vidyapeeth Deemed to be University College of Engineering Pune, Maharashtra, India Dr. Milind Gidde Professor, Civil Engineering Department, harati Vidyapeeth Deemed to be University College of Engineering Pune, Maharashtra, India P. D. Patil ssistant Professor, Civil Engineering Department, harati Vidyapeeth Deemed to be University College of Engineering Pune, Maharashtra, India STRCT around bridge supports (pier or abutment) can result in structural collapse and loss of property and life, for that reason there is a necessity to control and decrease the local scour. The study of local scour around bridge piers is very important for safe design of piers and foundation of bridges. The experiments were conducted in a 10 meter long, 0.30 meter wide and 0.45 meter deep tilting flume in P.G Hydraulic Laboratory of VDU College of Engineering, Pune. The flume was operated under the clear water condition using non uniform sand as a bed material. It has been observed that the reduction of maximum of scouring is highly dependent on shape of pier, sediment sample (uniform and non-uniform) and flow. The experiments were conducted on three different shapes of piers i.e. circular, diamond and elliptical, to investigate the effect of shape on local scour with nonuniform sand bed (Ϭg=1.6, d 50 =1.18 and Ϭg=2.0, d 50 =2.36) and flow of 14 cm and 16 cm. It was observed that elliptical shape pier has least scour than diamond and circular shapes for all operating conditions of experimentation. Keywords: Clear water, Flow, Non-uniform sand bed,, Shape of pier. Cite this rticle: Kamini hagwat Funde, Dr. Milind Gidde and P. D. Patil, Effect of Different Shapes of ridge Piers to Minimize Local, International Journal of Civil Engineering and Technology, 9(1), 2018, pp editor@iaeme.com

2 Kamini hagwat Funde, Dr. Milind Gidde and P. D. Patil 1. INTRODUCTION: is a natural phenomenon caused by erosive action of flowing water on the bed and banks of alluvial channels. In other words, is defined as the erosion of streambed sediment around an obstruction in a flow field. Cheremisinoff et al. (1987) defined scour as the lowering of the level of the river bed by water erosion, a tendency to expose the foundations of structures such as bridges. reusers et al. (1977) defined scour as a natural phenomenon caused by the flow of water in rivers and streams. ing mechanism has the potential to threaten the structural integrity of hydraulic structures and bridges. This may lead to ultimate failure when the foundation of the structures is undermined. series of bridge failures during floods due to pier scour has revived the importance of developing improved ways of protecting bridges against the ravages of scour. The construction of bridges in alluvial channels causes a contraction in the waterway at the bridge site. The contraction in the waterway might cause significant scour at that site. Hoffmans and Verheij (1997) have noted that local scour around bridge piers and foundations, as a result of flood flows, is considered to be the major cause of bridge failure. It occurs due to the intrusion of pier or abutment with the flow, which results in an increase of velocity of flow, creating vortices that take away the sediment material in surroundings of the bridge pier or abutment. Numerous experimental and numerical studies have been carried out by researchers in an attempt to quantify the equilibrium of scour in various types of soil material. Moreover, while a lot of work has been done to develop equations for predicting the of scour researchers have also worked extensively to understand the mechanism of scour. Current research areas include understanding the scour processes, temporal development of scour, predicting scour in cohesive soils, parametric studies of local scour, and prediction of scour at various shapes bridge piers. There are some of the researchers that have worked on pier scour. The current study reported herein is based on experiments carried out in an experimental channel at VUCOE University of Technology. The study was confined to nonuniform cohesion less material and clear-water flow conditions. dnan Ismael 1,Mustafa Gunal 2, Hamid Hussein 3 studied study on Effect of ridge Pier Position on Reduction ccording to Flow Direction[2]. The experiments included the study of new method to reduce scour in front of bridge pier by changing the position of bridge pier (named after here as downstream facing round nosed bridge pier)[5]. bdul-hassan K. l-shukur studied On Experimental Study of ridge Pier Shape to Minimize Local [5]. meer Talib 1, Zaid Hadi Obeid 2, Husam Kareem Hameed 3 stuided the New Imperial Equation for Local around Various ridge Piers Shapes in that experimental statistics for local scour around different shapes of bridge piers are presented [6]. J. S. ntunes do Carmo studied Experimental study on local scour around bridge piers in rivers [11]. Md. Mosabbir Pasha 1, ziz Hasan Mahmood 1, Shahriar Shams 2 studied n nalysis of ing Effects on Various Shaped ridge Piers [8]. The researcher P.T. Nimbalkar and Mr.Vipin Chandra studied on Estimation of ridge Pier for Clear Water & Live bed Condition [10]. 2. METHODOLOGY: Following methodology was used: 1. Determine scour around different shaped bridge piers experimentally using flume and find out pier shape which gives minimum scour and compare with other researches. 2. Take non uniform Sediment sample with different standard deviation. 3. To compare experimental results with different formulas. 4. To find out accuracy of result for that statistical analysis should be done editor@iaeme.com

3 Effect of Different Shapes of ridge Piers to Minimize Local 5. Plot the different graphs which shows scour variation around different shaped bridge piers and also they illustrate that variation between theoretical and experimental values. 3. EXPERIMENTL SETUP ND PROCEDURE: The experiments were carried out in Post Graduate Hydraulic Laboratory of harati Vidyapeeth Deemed to be University College of Engineering, Pune. Experiments were conducted in 10 m long, 0.30 m wide and 0.45 m deep flume. The re-circulating flow system was served by a 50hp. Pump are variable in speed and centrifugal which is locate at the downstream end of the flume. The flume slope will be adjusted as Test section of size 1 m long, 0.30 m wide and 0.11 m deep will be provided in the flume for laying the sediment sample. Two pointer gauges with Vernier, having precision of 0.1 mm were used at upstream as well as downstream of the test section to measure the water levels. Calibrated pigmy type of current meter was used to measure the point velocity. The V-notch will be used at downstream end of the tilting flume for measuring discharge. Piers were placed vertically at center of sediment zone. The sediment zone is leveled before starting tests. The control valve was adjusted in such a manner that clear water condition would get developed without causing any disturbance to the bed material. For each pier, experiments were conducted by keeping all experimental parameters same i.e. flow, bed slope and sediment. The experiments were run for six-hour duration during which scour s at the nose of the pier were measured at regular interval of time to study the temporal variation of scour. Details of experiments are summarized in Table 1.Sediment sample was prepared with noncohesive non-uniform sand having standard deviation σg = 1.6 & σ g = 2.Natural sand was sieved into different sizes and mixed according to the required proportions to achieve nonuniformity. Figure 1 Sketch for experimental setup editor@iaeme.com

4 Kamini hagwat Funde, Dr. Milind Gidde and P. D. Patil 4. SEDIMENT SMPLING: Non-cohesive river bed sand is used as sediment in the experimental work. Two samples of sediments are prepared as given below. Sample No: - 1 d 50 = 1.18 mm and Geometric standard deviation σ g = 1.6 Sample No: - 2 d 50 = 2.36 mm and Geometric standard deviation σ g = 2 σ g = Where, d 84 = Sediment size for which 84% by weight of sediment is finer. d 16 = Sediment size for which 16% by weight of sediment is finer Sediment nalysis: Geometric standard deviation used for classifying sediment as uniform or non-uniform. The standard deviations were calculated for two sediments in this thesis. The Geometric standard deviation value of 1.6 and 2 were used to classify sediment used in this thesis as non-uniform. 100% 90% 80% 70% % Finer 60% 50% 40% 30% 20% 10% 0% Grain 0.1 size (mm) log scale % Finer 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Grain Size (mm) log scale Chart 1 Illustration of sediment sample Chart 2 Illustration of sediment sample d 50 =1.18 mm. Ϭ g =1.6 d 50 =2.36 mm. Ϭ g =2 5. OSERVTIONS ND RESULTS efore the start of each experimental run, the model piers were set vertically at the desired locations in the flume sediment bed. The sediment bed around the model piers was fairly leveled and the water was then allowed to flow slowly over the sediment bed in the flume and the steady uniform flow conditions were achieved by operating the inlet supply valve and the tailgate. The experiments were run for Six-hour duration during which scour s at the nose of the pier were measured at regular interval of time to study the temporal variation of scour editor@iaeme.com

5 Effect of Different Shapes of ridge Piers to Minimize Local Figure 2 Schematic illustration of pier shapes (,, ) The summary of laboratory results that have been obtained from series tests conducted on the three pier shapes are shown in Table 1.The experiment study showed that scour drastically changed with changing the pier shape and flow velocity or flow. The results showed that the elliptical pier gives the lowest scour, while the diamond shape gives the largest scour. For Standard Deviation 6g=1.6, d50=1.18 and 6g=2, d50=2.36. Sr. No. Type of pier Table 1 Observations for Ϭg=1.6, 2. Discharge (Q) m 3 /s Depth of flow Velocity (V) m/s The above observation table 1 showed that, pier has a maximum scour than others shapes while the scour for elliptical has less scour. 6. NLYTICL NLYSIS: This study will evaluate the performance of the equations proposed by CSU equation, Laursen s equation. These two models were chosen because they are based on conventional regression techniques and are widely used by researchers and practicing engineers CSU equation: y b 2k k k k h b. F. Where: y sc =, m. h = Flow, m. b = Pier diameter, m. F = Froude number (F = V/(gh)^0.5). k 1 = Correction for pier shape (K1 = 1 for circular piers). k 2 = Correction for attack angle of approach flow (K2 = 1 for direct approach flow) editor@iaeme.com

6 Kamini hagwat Funde, Dr. Milind Gidde and P. D. Patil k 3 = Correction for bed form (K3 = 1.1 for clear-water scour). k 4 = Correction for armoring (K4 = 1 for sand bed material) Laursen s equation: Where: ys =, m. h = Flow, m. b = Pier diameter, m..!!." #!$ % & '!] Sr.No. Depth of flow Discharge (Q) m 3 /s Velocity (V) m/s Table 2 nalysis Table Type Of Pier Shape Measured Depth Theoretical Value Ϭ g =1.6 Ϭ g =2 CSU Laursen s The above table drawn which showed that comparison of the current study values of scour calculated by experimentally and theoretical values of CSU and Laursen s calculated from above equations Depth of flow=14 cm Deprh of flow =16 cm Measured Depth σg=1.6 Measured Depth σg=2 Therotical Value CSU Therotical Value Laursen s equation Chart 3 Illustration of nalysis. The above chart showed that illustration of current study result with theoretical results given by CSU (Colorado state university and Laursen s and the result showed that the experimental values are in range between these two theoretical values editor@iaeme.com

7 Effect of Different Shapes of ridge Piers to Minimize Local 7. VRITION OF LOCL SCOUR DEPTH WITH FLOW DEPTH ds/b y/b 5.50 present study CSU Laursen's present study CSU Laursen's present study CSU Laursen's Linear (present study ) Linear (CSU ) Linear (CSU ) ds/b y/b 5.50 present study CSU Laursen's present study CSU Laursen's present study CSU Chart 9 Comparative Variation of local scour (Ϭg=1.6) Chart 13 Comparative Variation of flow with flow with local scour (Ϭg=2) 8. STTISTICL NLYSIS: To find out accuracy of result for that statistical analysis should be done with nova statistical analysis software. The results comes from the statistical analysis for of flow 14cm, discharge and velocity shown in table 3,4,5 respectively and illustrate in charts 4.nd for of flow 16cm, discharge and velocity shown in table 6,7,8 respectively and illustrate in chart 5. 1). nalysis for of flow 14cm, discharge and velocity Table 3 Observation of Statistical analysis for flow =14 cm Sr No. Type of pier Depth of flow Discharge (Q) m3/s Velocity (V) m/s in Ϭg- 1.6 in Ϭg-2 µ 1 µ Hypothesis: Using level of significance α=0.05 H o : µ 1 = µ 2 H a : Not all the means are equal Where: µ 1 =mean number of scour using Ϭg-1.6 µ 2 = mean number of scour using Ϭg-2 nalysis Two-Factor without Replication: editor@iaeme.com

8 Kamini hagwat Funde, Dr. Milind Gidde and P. D. Patil Table 4 Summary of Statistical analysis for scour =14 cm SUMMRY Count Sum verage Variance (y-14) (y-14) (y-14) g= g nalysis Result Table: Source of Variation Table 5 Source of Variation of Statistical analysis for scour =14 cm Sum of squares degree of freedom means square P-value F crit Rows(Type of piers) (. 6g=1.6,2) Error Total ccuracy in type of pier % ccuracy between sample 6g-1.6, % 2) nalysis for of flow 16cm, discharge and velocity Sr No. Type of pier Table 6 Observations of statistical analysis for flow =16 cm. Depth of flow Discharge (Q) m 3 /s Velocity (V) m/s in Ϭg-1.6 in Ϭg-2 µ 1 µ nalysis Two-Factor without Replication: Table 7 Summary of statistical analysis for scour =16 cm. SUMMRY Count Sum verage Variance (y-16) (y-16) (y-16) g= g nalysis Result table: Source of Variation Table 8 Sources of Variation of statistical analysis for scour =16 cm Sum of squares degree of freedom means square fisherratio fisherratio P-value F crit Row(Type of piers) Column (. 6g=1.6,2) editor@iaeme.com

9 Effect of Different Shapes of ridge Piers to Minimize Local Error Total ccuracy in type of pier % ccuracy between sample 6g-1.6, % 5 6 scour (y-14) (y-14) (y-14) 6g =1.6 6g =2 scour (y-16) (y-16) (y-16) 6g= 1.6 6g= 2 Chart 4 Statistical nalysis for of flow 14 cm Chart 5 Statistical nalysis for of flow 16 cm Two way analysis of variance was conducted to evaluate the null hypothesis that there is no difference in pier shape and sample sour. In summary table elliptical pier average value is minimum it gives minimum scour as compare to circular, diamond pier and also average of sample of Ϭg=2 is minimum it gives sour minimum as compare to sample Ϭg=1.6 and from analysis table P-value give accuracy means null hypothesis. 9. PERCENTGE SCOUR DEPTH REDUCTION: The following table shows comparative percentage scour reduction between two flow conditions (y=14 cm and y=16cm) for sediment sample Ϭg=1.6. Sr.No Depth of flow Discharg e (Q) m 3 /s Table 9 Percentage reduction (6g=1.6) Velocity (V) m/s Type Of Pier Shape Measured Depth maximum scour % scour reduction The above chart showed that illustration of percentage scour reduction between the piers for sediment sample Ϭ=1.6.the showed that, the reduction of about 30% in local scour can be obtained by means of an elliptical shaped pier instead of with a diamond shaped pier and about 10% in local scour can be obtained by using an elliptical shaped pier instead of a circular shaped pier editor@iaeme.com

10 Kamini hagwat Funde, Dr. Milind Gidde and P. D. Patil The following table shows comparative percentage scour reduction between two flow conditions (y=14 cm and y=16cm) for sediment sample Ϭg=2. Table 10 Percentage reduction (6g=2) Sr. No. Depth of flow Discharge (Q) m 3 /s Velocity (V) m/s Type Of Pier Shape Measured Depth maximum scour % scour reduction % scour reduction % scour reduction % scour reduction % scour reductio n Chart 6 Illustration of Percentage reduction (6g=1.6) Chart 7 Illustration of Percentage reduction (6g=2) The above chart showed that illustration of percentage scour reduction between the piers for sediment sample Ϭ=2.the showed that, the reduction of about 32% in local scour can be obtained by means of an elliptical shaped pier instead of with a diamond shaped pier and about 20% in local scour can be obtained by using an elliptical shaped pier instead of a circular shaped pier. 10. CONCLUSIONS The analysis is performed to get the variables affecting the local scour around bridge piers. The flow in channel, flow velocity, and pier shape has a direct effect on local scour as mentioned in literature review. There are several investigators studied on local scour around bridge pier but most of the studies are restricted to uniform sediments. In this study, the local scour round the different bridge piers in non-uniform sediments has been studied experimentally. Main intention of study was to investigate effect of pier's shape as protecting measure against local scour, through a series of experiment on different shapes like circular, elliptical and diamond. The experimental result concluded that, 1) For scour y=14cm the minimum of scour occurs while for y=16cm the maximum of scour occurs. Hence the of scour increases with the increasing the down-flow (as the velocity increasing) and vice versa editor@iaeme.com

11 Effect of Different Shapes of ridge Piers to Minimize Local 2) The effect of size dimension of the bed material on the scour is more significant. For given flow conditions the sediment sample Ϭg=1.6 the maximum scour occurs while for Ϭg=2 occurs minimum scour. Hence we concluded that, when standard deviation of bed material is large, scour will be smaller means that, scour should be decrease with increase in sediment size. 3) In comparison of the scour results in two flow conditions(y=14cm & y=16cm) and two sample conditions (Ϭg=2 & Ϭg=1.6) the reduction of about 30% in local scour can be obtained by means of an elliptical shaped pier instead of with a diamond shaped pier and about 15% in local scour can be obtained by using an elliptical shaped pier instead of a circular shaped pier. 4) The measured scour of pier models in this study agreed well with the calculated scour from theoretical equations (Colorado state university) CSU and Laursen. 5) Finally the experimental analysis concluded that, the elliptical pier has lower scour as compare to other shapes. Since elliptical pier is best protecting measure against local scour instead of other conventional shapes like circular and diamond. REFERENCES [1] bdul Karim arbhuiya nd Subhasish Dey (5 July 2003); Revised 13 ugust 2004 Local t butments: Review Sadhana Vol. 29, Part 5, October 2004, Pp Printed In India. [2] dnan Ismael, Mustafa Gunal, Hamid Hussein Influence of ridge Pier Position ccording To Flow Direction on Reduction Isbn: Doi: / _24. [3] dnan Ismael, Mustafa Gunal, Hamid Hussein (2015) Effect of ridge Pier Position on Reduction ccording to Flow Direction rab J Sci Eng 40: DOI /s x. [4] li Tafarojnoruz, Roberto Gaudio (Iahr Member), Subhasish Dey (Iahr Member) (2010) Flow-ltering Countermeasures against at ridge Piers: Review Journal of Hydraulic Research Vol.48, No.4, Pp Doi: / # International ssociation for Hydro-Environment Engineering nd Research. [5] l-shukur, bdul-hassan K. and Obeid, Z.H. (2016) Experimental Study of ridge Pier Shape to Minimize Local, International Journal of Civil Engineering and Technology, 7(1), pp [6] meer Talib, Zaid Hadi Obeid, Husam Kareem Hameed (2013) New Imperial Equation for Local around Various ridge Piers Shapes International Journal of Science and Research (IJSR) ISSN (Online): [7] Md. Mosabbir Pasha, ziz Hasan Mahmood, Shahriar Shams (December 2013) n nalysis Of ing Effects On Various Shaped ridge Piers runei Darussalam Journal Of Technology nd Commerce. Volume 7 Number 1. [8] Mubeen eg, Salman eg (May 2013) Reduction around ridge Piers: Review International Journal of Engineering Inventions E-Issn: , P-Issn: Volume 2, Issue 7 Pp: [9] P.T. Nimbalkar and Mr.Vipin Chandra, (2013) Estimation of ridge Pier for Clear Water & Live bed Condition, International Journal of Civil Engineering and Technology, 4(3), pp [10] J. S. ntunes Do Carmo (2005) Experimental Study On Local round ridge Piers In Rivers Wit Transactions On Ecology nd The Environment, Vol 83, Wit Press Issn editor@iaeme.com