Lokal oyulmayı azaltmak amacıyla iki köprü ayağı tipi için geometrik iyileştirme

Abstract

Köprü ayakları çevresinde oluşan lokal oyulma, köprü çökmelerinde ve köprülerde meydana gelen ağır hasarlarda kritik bir rol oynamaktadır. Birçok araştırmacı lokal oyulma sorununu incelemiştir. Ancak, çalışmaların çoğunluğu sadece karmaşık akım davranışının incelenmesine odaklanmış, herhangi bir yapısal kısıta bağlı olmayan ve inşa zorluklarını göz ardı eden yeni köprü ayağı tasarımları önerilmiştir. Bu çalışmada, sıklıkla kullanılan konvansiyonel köprü ayağı tiplerine uygulanan geometrik iyileştirmelerin, nehir yatağında oyulmaya neden olan akım parametreleri üzerindeki etkilerinin incelenmesi amaçlanmıştır. Referans geometrilerin etrafını dolaşan, herhangi bir taşıyıcı özelliği olmayan dik üçgen biçimindeki eklentiler uygulanmıştır. Söz konusu dik üçgen biçimindeki eklentiler uzunlukları cinsinden parametrize edilmiş ve uygulanan farklı modifikasyonlar arasından en iyi seçeneğin ortaya çıkarılması için ardışık nümerik çözümler gerçekleştirilmiştir.
Değişiklik yapılan geometrilerin performansı, oyulmayı tetikleyen ve gelişiminden sorumlu olan iki önemli akım parametresi olan nehir yatağına etkiyen basınç ve kayma gerilmesi değerleri üzerinden değerlendirilmiştir. Sonuçlar, küçük yükseklik ve büyük genişlik değerine sahip konik eklentilerin, nehir yatağına etkiyen maksimum basınç ve kayma gerilmelerini düşürmesi bakımından daha etkili olduğunu göstermiştir

Keywords

• HAD
• köprü ayağı
• oyulma
• modelleme

Geometric improvement for two bridge pier types to reduce local scour

Abstract

Local scour around the bridge piers play a critical role in collapse and heavy damages on bridges. Many researchers have studied local scour problem. However, majority of the studies only focused on examination of the complex flow structure and offering new pier geometry designs without any structural restrictions, which ignore construction difficulties. This study attempts to investigate the effect of geometric enhancements on commonly used conventional pier types to reduce scour related flow parameters acting on riverbed. A right triangular implementation that wraps the reference shapes were accordingly applied as non-load bearing curtain walls. Triangular implementation has been parametrized by its leg lengths and successive numerical analyses were conducted to reveal the better option among different modifications.
Performance of the modified piers were compared in terms of pressure and the bed shear stresses acting on riverbed representing the two important flow forces that are responsible for triggering and developing scour. The results show that low height values with high width values of conical implementations perform better in terms of reducing maximum pressure and shear stress acting on riverbed.

Keywords

• CFD
• bridge pier
• scour
• modeling

References

1. Shirole, A.M. and Holt, R.C., Planning for a comprehensive bridge safety assurance program, Transportation Research Record, 1290, 39-50, (1991)
2. Briaud, J.L., Ting, F.C., Chen, H.C., Gudavalli, R., Perugu, S. and Wei, G., SRICOS: Prediction of scour rate in cohesive soils at bridge piers, Journal of Geotechnical and Geoenvironmental Engineering, 125, 4, 237-246, (1999).
3. Wardhana, K. and Hadipriono, F.C., Analysis of recent bridge failures in the United States, Journal of Performance of Constructed Facilities, 17, 3, 144-150, (2003).
4. Melville, B.W. and Sutherland, A.J., Design Method for Local Scour at Bridge Piers, Journal of Hydraulic Engineering, 114, 10, 1210–1226, (1988).
5. Melville, B.W. and Chiew, Y., Time Scale for Local Scour at Bridge Piers, Journal of Hydraulic Engineering, 125, 1, 59–65, (1999).
6. Yanmaz, A.M. and Altinbilek, H.D., Study of Time‐Depenbent Local Scour around Bridge Piers, Journal of Hydraulic Engineering, 117, 10, 1247–1268, (1991).
7. Yanmaz M.A., Uncertainty of Local Scouring Parameters Around Bridge Piers, Turkish Journal of Engineering and Environmental Science. 25, 127-137, (2001).
8. Kothyari U.C., Garde R.J. and Ranga R.K.G., Temporal variation of scour around cylindrical bridge piers, Journal of Hydraulic Engineering, 118, 8, 1091−1106, (1992).

9. Kandasamy J.K. and Melville B.W., Maximum local scour depth at bridge piers and abutments, Journal of Hydraulic Research, 36, 183−197, (1998).
10. Richardson, J.E. and Panchang, V.G., Three-Dimensional Simulation of Scour-Inducing Flow at Bridge Piers, Journal of Hydraulic Engineering, 124, 5, 530–540, (1998).
11. Salaheldin, T.M., Jasim, I. and Mohammad, H.C., Numerical Modeling of Three-Dimensional Flow Field Around Circular Piers, Journal of Hydraulic Engineering, 130:91-100, (2004).
12. Zhu Z.and Liu, Z., CFD prediction of local scour hole around bridge piers, Journal of Central South University, 19, 273−281, (2012).
13. Xiong, W., Cai, C.S., Kong, B. and Kong, X., CFD simulations and analyses for bridge-scour development using a dynamic-mesh updating technique, Journal of Computing in Civil Engineering, 30, 1, 04014121, (2016).
14. Nasr-Allah, T.H., Moussa, Y.A.M, Abdel-Aal, G.M. and Awad, A.S., Experimental and numerical simulation of scour at bridge abutment provided with different arrangements of collars, Alexandria Engineering Journal, 55, 1455–1463, (2016).
15. Li, J. and Tao, J., CFD-DEM Two-Way Coupled Numerical Simulation of Bridge Local Scour Behavior under Clear-Water Conditions, Transportation Research Record, 2672, 39, 107-117, (2018).
16. Chiew, Y., Scour Protection at Bridge Piers, Journal of Hydraulic Engineering, 118, 9, 1260–1269, (1992).
17. Kumar, V., Kittur, G.R.R. and Nandana, V., Reduction of local scour around bridge piers using slots and collars, Journal of Hydraulic Engineering, 125, 1302-1305, (1999).
18. Zarrati, A.R., Gholami, H. and Mashahir, M.B., Application of collar to control scouring around rectangular bridge piers, Journal of Hydraulic Research, 42, 1, 97-103, (2004).
19. Fotherby, L.M., Alternatives to riprap for protection against local scour at bridge piers, Transportation Research Record, 1420: 32-39, (1993).
20. Pasha, M., Mahmood, A.H. and Shams, S., An Analysis of Scouring Effects on Various Shaped Bridge Piers, Brunei Darussalam Journal of Technology and Commerce, 7, 29-42, (2013).
21. Vijayasree, B.A., Eldho, T.I., Mazumder, B.S.and Ahmad, N., Influence of bridge pier shape on flow field and scour geometry, International Journal of River Basin Management, 17, 1, 109-129, (2019).
22. Yagci, O., Yildirim, I., Celik, M.F., Kitsikoudis, V., Duran, Z. and Kirca, V.S.O., Clear water scour around a finite array of cylinders, Applied Ocean Research., 68, 114–129, (2017).
23. Li, J. and Tao, J., Streamlining of bridge piers as scour countermeasures: optimization of cross sections, Transportation Research Record, 2521, 1, 162-171, (2015).
24. Li, J., Tao, J. and Yu, X., Streamlining of Bridge Pier as a Scour Countermeasure: A Feasibility Study, Proc. International Foundations Congress and Equipment Exposition, 319–329, (2015).
25. Koken, M. and Constantinescu, G., Flow and Turbulence Structure Around Abutments with Sloped Sidewalls, Journal of Hydraulic Engineering, 140, 7, 04014031, (2014).
26. Roulund, A., Sumer, B. M., Fredsoe, J., and Michelson, J., Numerical and experimental investigation of flow and scour around a circular pile, Journal of Fluid Mechanics, 534, 351–401, (2005).
27. Simpson, R.L., Junction flows, Annual Review of Fluid Mechanics, 33, 1, 415-443, (2001).
28. Chang, W.Y., Constantinescu, G., Lien, H.C., Tsai, W.F., Lai, J.S. and Loh, C.H., Flow structure around bridge piers of varying geometrical complexity, Journal of Hydraulic Engineering, 139, 8, 812-826, (2013).