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Academic literature on the topic 'LOCAL SCAUR'
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Dissertations / Theses on the topic "LOCAL SCAUR"
1
Hong, SeungHo. "Interaction of Bridge Contraction Scour and Pier Scour in a Laboratory River Model." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7533.
Full textAbstract:
The engineering design of a hydraulic structure such as a river bridge requires consideration of the factors that affect the safety of the structure. Among them, one of the most important variables is bridge foundation scour. However, engineering experience seems to indicate that computation of scour depth using current scour formulas tends to overpredict scour in comparison to field measurements. The result can be an overdesigned bridge foundation that increases the cost of the bridge. One possible reason for the overprediction is the current practice of adding separate estimates of contraction scour and pier scour when in fact these processes occur simultaneously and interact.
During the occurrence of a flood, velocities and depths increase but they are affected by changes in the distribution of discharge between the main channel and floodplain. In addition, the time history or time development of contraction scour and local pier scour is not the same. As a result, the influence of contraction scour on pier scour, for example, is time dependent.
Laboratory experiments are proposed using a 1:45 scale hydraulic model of the Ocmulgee River bridge at Macon, Georgia. Initially, the contraction scour will be measured without the bridge piers in place. In this experiment, the time history of the scour and the velocity distributions at the equilibrium state will be measured. Then the piers will be placed at the bridge cross-section in the flume, and the same measurements will be made. The sensitivity of the measurements to small changes in depth at the same discharge will also be determined, and comparisons will be made with field measurements of scour depth. The results will be used to assess the relative contribution of contraction scour and local pier scour to the final design of the bridge foundation depth.
2
Lavictoire, Alexandra. "Bore-Induced Local Scour around a Circular Structure." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/31950.
Full textAbstract:
Recent natural disasters, such as major tsunamis, have prompted researchers and practicing engineers to improve their understanding of the impacts of bore-like waves on structures and their foundations. The high velocity and the relatively short duration of hydraulic bores causes local scouring which is different from that generated by river flows and waves. The present study uses an experimental model to simulate the propagation of a hydraulic bore over a movable sediment bed placed around a circular pier-like structure. Measurements of water surface elevation, bore propagation velocity and scour distribution were taken. The linear relationship between reservoir depth and bore depth led to an increase in flow acceleration, and thus to an increase in flow velocity. Final scour bed elevations indicated that scour depth was highly dependent on the bore velocity. The scour depth ratios suggested in current design guidelines were significantly lower than those obtained in this study.
3
Li, Junhong Li. "Pier Streamlining as a Bridge Local Scour Countermeasure and the Underlying Scour Mechanism." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1518565785864439.
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Kabir, Alamgir. "Modelling local scour around bridge piers using TELEMAC." Thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/6683.
Full textAbstract:
Scour at bridge crossings is a major cause of bridge failure. There are several different types of scour such as general scour, constriction scour and local scour. One of the most serious types is local scour which occurs as a result of vortex formation around bridge piers and abutments (Hoffmans & Verheij, 1997; Raudkivi, 1998; Melville & Coleman, 2000; Richardson & Davis, 2001; Armitage & McGahey, 2003). Local scour is also one of the most difficult to predict accurately. If not adequately designed for, local scour of a riverbed at a bridge pier may become deep enough to undermine the pier foundation and eventually cause the bridge to collapse. Complete protection against scour is expensive and therefore not a favourable design option. It is generally cheaper to ensure that the foundation lies below the maximum expected scour depth. Traditionally, the maximum scour depth is predicted from empirical equations derived from simple laboratory tests without much regard for local conditions. Alternatively, smaIlscale hydraulic models, which are laborious and time intensive, are widely used. In view of the above, increasing attention is being paid to the use of Computational Fluid Dynamics (CFD) based modelling for the prediction of local scour and its opposite, local deposition. The ever-improving capabilities of computers and the increasing availability of powerful and flexible CFD codes have further assisted in this process. This study is a contribution in this direction.
5
Ozalp, Murat Can. "Experimental Investigation Of Local Scour Around Bridge Pier Groups." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615594/index.pdf.
Full textAbstract:
It is an important task that design engineers in practice predict the local scour around bridge piers as accurately as possible because excessive local scour around bridge piers unbalance and demolish the bridges. Many equations have been proposed previously by various researchers, based on their experimental findings, but no general method has been developed so far due to the complexity of the topic. In the present study two new bridge pier groups were employed to investigate the inclination effect of the most upstream and downstream piers on the local scours around all piers. Total of 72 experiments have been conducted with 3 inclination angles, one of which representing the vertical case, each experiment lasting 6 hours, under uniform flow and clear-water conditions for a range of water depths and flow velocities on the uniform bed material. It is clearly observed and measured that the amount of local scour reduces substantially by the effect of inclination in the group piers, especially the reduction in the scour around the most upstream pier is found notable. Based on the experimental data, regression analyses are made and an empirical scour depth equation is developed for each individual pier in the pier groups studied. Comparisons with the similar studies performed by other researchers have been made and the results discussed.
6
Lee, Seung Oh. "Physical modeling of local scour around complex bridge piers." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/29398.
Full textAbstract:
Thesis (Ph.D)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006.<br>Committe Chair: Terry W. Sturm; Committe Members: Dr. Fotis Sotiropoulos; Committee Members: Dr. Philip J. Roberts; Committee Members: Dr. Donald R. Webster; Committee Members: Dr. Anthony Hayter. Part of the SMARTech Electronic Thesis and Dissertation Collection.
7
Daskin, Sueyla. "Effects Of Collars On Local Scour Around Semi-circularend Bridge Abutments." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613310/index.pdf.
Full textAbstract:
During severe floods, bed material around bridge piers and abutments are scoured by the flow and as a result, bridges are subject to damages. These damages are mostly unrepairable and can result in loss of lives and property. In this thesis study,
abutment scour under clear-water condition was investigated and collars were tested as scour countermeasures around the abutments. The experimental study was carried out in a rectangular channel with an almost uniform cohesionless bed material of d50=1.50 mm for a test period of 3-hours. The channel was 28.5 m long and 1.5 m wide. The erodible bed material was placed into the test section that was 5.8 m long
and 0.48 m deep.
For this thesis study, 60 experiments were carried out with and without various collars placed at different elevations around the abutments. The scour formation around the abutments with collars was observed and scour reduction efficiencies of the collars were studied. Experiment results were compared with the previous studies of Dogan (2008) and Kayatü<br>rk (2005) in terms of sediment size, abutment shape and flow depth, and the effects of these factors on collar'<br>s scour reduction efficiency were studied. Based on the results of the experimental studies, it was observed that scour
depths decreased as the collar width increased and the collar placed deeper into the sediment bed for a given abutment length. When the present study and the previous studies were compared, it was observed that sediment size and flow depth had no significant effect on the scour reduction performances of the collars.
8
Cesme, Murat. "Experimental Investigation Of Local Scour Around Inclined Dual Bridge Piers." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12606597/index.pdf.
Full textAbstract:
For a bridge engineer, it is very important to estimate the maximum scour depth around the piers as accurately as possible, in order to design the footing safely. Many experimental studies have been performed by several investigators until now, in order to obtain information about scouring mechanism. The aim of this experimental study is to examine the effect of inclination of the dual bridge piers on scour depth. The experiments have been conducted with dual pier models under clear-water conditions, for various uniform flow depths. Scour depths had been measured at four different points around the piers<br>namely upstream and downstream faces of both piers. Dimensional and non-dimensional scour curves have been developed and presented to show the temporal variation of scour depth. The depths of local scour around inclined piers have been observed to be smaller than the scour depths around vertical piers.
9
Ghoma, Mohamed Ibrahem. "The effect of wall jet flow on local scour hole." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5501.
Full textAbstract:
This thesis reports on investigations carried out to study of the effect of horizontal wall jets on rough, fixed and mobile beds in open channel flow. Experimental tests were carried out, using fixed and mobile sediment beds. Computer simulation models for the flow within the jet and resulting sediment transport were developed and their results analysed in this study. In the experimental phase, tests were carried out with both fixed and mobile sediment beds. The shape of the water surface, numerous point velocity measurements and measurements of the evolving scour hole shape were made. Detailed descriptions of the turbulent flow field over a fixed rough bed and for scour holes at equilibrium were obtained for a range of initial jet conditions. Fully turbulent, multiphase flow was modelled using the Fluent Computational Fluid Dynamics software. This was used to analyze the flow caused by a jet in a rectangle open-channel with a rough bed, and also the flow pattern in a channel with a local scour hole. The volume of fluid (VOF) multiphase method and K- model was used to model the fluid flow in both cases. The model predictions of velocity and shear stress were compared against experimental observations. The experimental data was used to develop new empirical relationships to describe the pattern of boundary shear stress caused by a wall jet over fixed beds and in equilibrium scour holes. These relationships were linked with existing bed-load transport rate models in order to predict the temporal evolution of scour holes. An analytical model describing the relationship between the wall jet flow and the development of a local scour hole shape was reported and its predictions compared with experimental data.
10
Cunninghame, Margaret. "Numerical modelling of local scour in rivers using fluent 6.2." Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/5057.
Full textAbstract:
Includes bibliographical references.<br>Scour and deposition are natural processes which take place in a river as the stream profile adjusts to changing flow rates, sediment loads and other environmental conditions. Man-made obstacles to the stream flow such as bridge piers and abutments and other hydraulic structures alter flow patterns causing local scouring and deposition. Excessive scour undermines the foundations of bridges and other fluvial structures which may ultimately cause their collapse. Reliable methods are needed to model the complex flow features at bridge piers and abutments and hence predict the associated patterns of local scour. Empirical formulae are notoriously inconsistent in their predictions of local scour depth (Johnson, 1995) while physical modelling is time-consuming and therefore expensive.