scholarly journals Steady and unsteady pressure scour under bridges at clear-water conditions

2016 ◽  
Vol 43 (4) ◽  
pp. 334-342 ◽  
Author(s):  
Serife Yurdagul Kumcu
Keyword(s):  
Bridge Deck ◽  
Transportation Network ◽  
Water Pressure ◽  
Clear Water ◽  
Flow Conditions ◽  
Experimental Conditions ◽  
Pressure Flow ◽  
Equilibrium Pressure ◽  
Sediment Size ◽  
Pressure Scour

Bridges are vital components of the transportation network and if they are damaged or destroyed during a flood, they isolate communities and limit movement of supplies and emergency services. Evaluating their constructional stability and structural response after a flood event is critical for bridge safety. Bridge studies are usually designed with an assumption of an open channel flow condition, but the flow regime can switch to pressure flow if the downstream edge of a bridge deck is partially or totally submerged during a large flood. The main goal of this paper is to study the pressurized flow scour under a bridge deck and downstream deposition that results from eroded sediment material governed by both steady and unsteady clear-water flow conditions. Experimental conditions used in this study involve clear-water scour of a sand bed of given median sediment size d50 = 0.90 mm and sediment uniformity σg = 1.29, an approach flow characterized by a flow depth and velocity, a rectangular-shaped bridge deck, and a stepwise flood hydrograph defined by its time to peak and peak discharge. Different flow conditions were considered in confined flow under the bridge deck. Relationship between pressure-flow scour and flow conditions is presented and discussed under the obtained experimental data. Additionally, effects of single-peaked stepwise flow hydrographs (unsteady flow conditions) on bridge pier scour depth are investigated under clear-water pressure-flow conditions, whereas previous researches mainly focused on the equilibrium pressure scour under steady flow conditions.

Pressure flow and weir scour beneath a bridge deck

2019 ◽  
Vol 46 (6) ◽  
pp. 534-543
Author(s):  
Musteyde Baduna Kocyigit ◽  
Onur Karakurt
Keyword(s):  
Bridge Deck ◽  
Flow Depth ◽  
Clear Water ◽  
Hole Depth ◽  
Sediment Size ◽  
Bridge Model ◽  
Weir Flow ◽  
Water Conditions ◽  
Scour Hole ◽  
Series Of Experiments

In this study, a series of experiments in a flume was conducted to investigate the maximum scour hole depth that occurred due to the vertical contraction of the flow underneath a bridge deck model without a pier. The bridge model was tested under pressurized and weir type of flows governed by clear water conditions. Various parameters of flow, sediment, and geometric features of the bridge, such as approach flow depth, discharge, sediment size, girder depth and degree of submergence were varied to investigate their effects on the maximum depth of scour hole. A total of 102 experiments were conducted and two empirical equations were developed separately for pressure and weir flow types with the use of experimental data. Effects of the aforementioned parameters on the scour hole were also analyzed and discussed.

Experimental investigation of the effect of skew angle on partially or fully submerged deck scour

2020 ◽  
Vol 47 (9) ◽  
pp. 1027-1036
Author(s):  
Müsteyde Baduna Koçyiğit ◽  
Önder Koçyiğit ◽  
Hüseyin Akay ◽  
Gülay Demir
Keyword(s):  
Experimental Data ◽  
Bridge Deck ◽  
The Other ◽  
Flow Depth ◽  
Clear Water ◽  
Flow Conditions ◽  
Skew Angle ◽  
Hole Depth ◽  
Scour Hole ◽  
Contraction Scour

This paper presents the results of an experimental study investigating the effect of skew angle on clear-water contraction scour under a bridge deck at partially and fully submerged flow conditions. Two bridge deck models without a pier, one of which was located perpendicular to the flow while the other one was located with skewness of 15°, were used in the study. Forty experiments were performed for each deck model, 24 of which were under partially submerged and 16 were under fully submerged flow conditions. Analysis of the experimental data showed that as the discharge and approach flow depth increased, the maximum scour hole depth under the skewed deck model increased up to 25%–66% for fully submerged flow and 17%–57% for partially submerged flow conditions. Furthermore, the effect of skew angle significantly enlarged the width of the scour hole as you move along the skewed deck.

scholarly journals Effect of various flow, sediment and geometrical parameters on partially or fully submerged deck scour

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Müsteyde Baduna Koçyiğit ◽  
Onur Karakurt ◽  
Hüseyin Akay
Keyword(s):  
Maximum Depth ◽  
Geometrical Parameters ◽  
Flow Depth ◽  
Clear Water ◽  
Flow Conditions ◽  
Flow Area ◽  
Sediment Size ◽  
Scour Hole ◽  
Series Of Experiments ◽  
Hole Effect

AbstractThe effect of various parameters of flow, sediment and geometric features of the bridge on the depth and shape of the scour hole occurred underneath a bridge deck model without a pier was investigated by a series of experiments conducted in a flume under partially and fully submerged flow and clear water conditions. The experiments were performed with factors such as approach flow depth, discharge, sediment size, degree of submergence, girder location and depth. A total of 112 experiments were conducted for both partially and fully submerged flow conditions. The experimental data showed that the partially submerged flow increased the maximum depth of scour hole and affected the shape of the scour hole more when compared to the fully submerged flow. It was also noted that parameters that directly affected flow structure in the bridge opening such as girder height might significantly increase the maximum depth of scour hole. Effect of the distance between a single girder and the bridge edge was also tested by using three different girder location and it was found that as the distance increased, the depth of the scour hole decreased and the location of the maximum scour depth moved with the girder to where the contraction in the flow area occurred.

scholarly journals Durability of Road and Bridge Concrete and Spray-Coating Waterproof Material

2021 ◽  
Vol 31 (4) ◽  
pp. 227-235
Author(s):  
Liang Wei
Keyword(s):  
Bridge Deck ◽  
Water Pressure ◽  
Spray Coating ◽  
Internal Force ◽  
Drain Pipe ◽  
The Road ◽  
Before And After ◽  
High Elongation ◽  
Research Gap ◽  
The Impact

Different from traditional waterproof methods for road and bridge concrete, the spray-coating waterproof material can effectively prevent rainwater and other corrosive liquids from entering the concrete structure, and it has a few functional advantages such as anti-carbonization, resistance to sulfate attack, and high elongation. Existing studies have discussed the impact of the microstructure of waterproof material on the structure of waterproof coating, the optimization of the mix ratios of waterproof material, and the influencing factors of the waterproof performance of waterproof material, etc., however, few researches have concerned about the mechanical properties of concrete after coated with the spray-coating waterproof material. Therefore, to fill in this research gap, this paper researched the durability of road and bridge concrete and the spray-coating waterproof material. At first, it analyzed the bridge deck water pressure and the internal force of the drain pipe structure under multiple drainage methods, and calculated the water pressure at the gutter inlet, the stress, and the permeability coefficient of the waterproof coating. Then, this paper elaborated on the experimental methods for measuring the durability of the road and bridge before and after coated with the spray-coating waterproof material, and introduced the methods for testing the waterproof material and the concrete. At last, this paper gave the corresponding experimental results, the analysis, and the conclusion.

Clear-water local scour at wide piers in shallow-water flow

2014 ◽  
Vol 9 (3) ◽  
pp. 331-343 ◽  
Author(s):  
N. Ahmad ◽  
T. Mohamed ◽  
F. H. Ali ◽  
B. Yusuf
Keyword(s):  
Laboratory Data ◽  
Local Scour ◽  
The Other ◽  
Scour Depth ◽  
Temporal Development ◽  
Clear Water ◽  
Shallow Water Flow ◽  
Equilibrium Time ◽  
Sediment Size ◽  
Flow Intensity

Laboratory data for local scour depth regarding the size of wide piers are presented. Clear water scour tests were performed for various pier widths (0.06, 0.076, 0.102, 0.14 and 0.165 m), two types of pier shapes (circular and rectangular) and two types of uniform cohesionless bed sediment (d50 = 0.23 and d50 = 0.80 mm). New data are presented and used to demonstrate the effects of pier width, pier shape and sediment size on scour depth. The influence of equilibrium time (te) on scouring processes is also discussed. Equilibrium scour depths were found to decrease with increasing values of b/d50. The temporal development of equilibrium local scour depth with new laboratory data is demonstrated for flow intensity V/Vc = 0.95. On the other hand, the results of scour mechanism have shown a significant relationship between normalized volume of scoured and deposited with pier width, b. The experimental data obtained in this study and data available from the literature for wide piers are used to evaluate predictions of existing methods.

Abutment scour in clear-water and live-bed conditions by GMDH network

2013 ◽  
Vol 67 (5) ◽  
pp. 1121-1128 ◽  
Author(s):  
Mohammad Najafzadeh ◽  
Gholam-Abbas Barani ◽  
Masoud Reza Hessami Kermani
Keyword(s):  
Back Propagation ◽  
Support Vector ◽  
Group Method ◽  
Scour Depth ◽  
Back Propagation Algorithm ◽  
Clear Water ◽  
Sediment Size ◽  
Svm Model ◽  
Vector Machines ◽  
Abutment Scour

In the present study, the Group Method of Data Handling (GMDH) network has been utilized to predict abutments scour depth for both clear-water and live-bed conditions. The GMDH network was developed using a Back Propagation algorithm (BP). Input parameters that were considered as effective variables on abutment scour depth included properties of sediment size, geometry of bridge abutments, and properties of approaching flow. Training and testing performances of the GMDH network were carried out using dimensionless parameters that were collected from the literature. The testing results were compared with those obtained using the Support Vector Machines (SVM) model and the traditional equations. The GMDH network predicted the abutment scour depth with lower error (RMSE (root mean square error) = 0.29 and MAPE (mean absolute percentage of error) = 0.99) and higher (R = 0.98) accuracy than those performed using the SVM model and the traditional equations.

An initial assessment of bed destabilization risk past vegetation patches using instrumented particles

2021 ◽  
Author(s):  
Yi Xu ◽  
Valyrakis Manousos ◽  
Panagiotis Michalis
Keyword(s):  
Initial Assessment ◽  
Flow Structures ◽  
Clear Water ◽  
Flow Conditions ◽  
Flow Parameters ◽  
Water Conditions ◽  
The Mean ◽  
Acoustic Doppler Velocimetry ◽  
Patch Density ◽  
Vegetation Patches

<p>Instream vegetation may alter the mean and turbukent flow fields leading to destabilizing riverbed surface, under certain flow conditions. In particular, recent research on instream vegetation hydrodynamics and ecohydrogeomorphology has focused on how energetic flow structures and bulk flow parameters downstream a vegetation may result in riverbed destabilization. This study, demonstrated the application of a 20mm novel instrumented particle in recording entrainment rates downstream simulated vegetation patches of distinct densities, at various distances downstream these. A patch of 6mm acrilic cylinders is used to simulate the emergent vegetation having the same diameter (12cm) and different porosities or densities (void volume equal to 1.25%, 3.15%, 6.25%, 11.25%, and 17.25%). The flow velocity near the instrumented particle is recorded using acoustic Doppler velocimetry (ADV) with appropriate seeding, under clear water conditions. Preliminary results are presented with focus on the effect of vegetation patch density on the flow field and subsequent effects on particle entrainment rates and implications for bed surface destabilisation.</p>

scholarly journals Uremic platelets have a functional defect affecting the interaction of von Willebrand factor with glycoprotein IIb-IIIa

Blood ◽  
1990 ◽  
Vol 76 (7) ◽  
pp. 1336-1340 ◽  
Author(s):  
G Escolar ◽  
A Cases ◽  
E Bastida ◽  
M Garrido ◽  
J Lopez ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Platelet Adhesion ◽  
Indirect Evidence ◽  
Flow Conditions ◽  
Experimental Conditions ◽  
Shear Rates ◽  
Functional Defect ◽  
Uremic Patients ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Uremic patients have an impaired platelet function that has been related to membrane glycoprotein (GP) abnormalities. Using a perfusion system, we have studied the interaction of normal and uremic platelets with vessel subendothelium (SE) under flow conditions. Reconstituted blood containing washed platelets, purified von Willebrand factor (vWF) (1 U/mL), and normal washed red blood cells was exposed to de- endothelialized rabbit segments for 10 minutes at two different shear rates (800 and 1,600 seconds-1). In some experiments a monoclonal antibody to the GPIIb-IIIa complex (EDU3) was added to the perfusates. With normal platelets, the percentage of the vessel covered by platelets (%CS) was 23.1% +/- 3.7% at 800 seconds-1 and 30% +/- 4.3% at 1,600 seconds-1. Platelets were observed in contact or forming monolayers on vessel SE. EDU3 inhibited the spreading of normal platelets. The %CS (11.1% +/- 3.3%) was statistically decreased (P less than .01) and most of the platelets were observed in contact with the vessel surface. These data indicate that, under flow conditions, the interaction of vWF with GPIIb-IIIa can support the spreading of normal platelets in the absence of exogenous fibrinogen. Under the same experimental conditions, the interaction of uremic platelets with SE was markedly impaired at both shear rates studied (P less than .01 v normal platelets). The presence of EDU3 did not modify the interaction of uremic platelets. These results confirm the impairment of the platelet adhesion observed in uremic patients. Furthermore, they indicate the presence of a functional defect in the interaction of vWF with GPIIb-IIIa. The fact that perfusions with normal and uremic platelets in the presence of an antibody to the GPIIb-IIIa complex did not show any differences gives indirect evidence on a functionally normal interaction vWF/GPIb in uremic patients.

scholarly journals Boulder Pickup by Tsunami Surge

2019 ◽  
Vol 13 (05n06) ◽  
pp. 1941006
Author(s):  
Samuel Harry ◽  
Margaret Exton ◽  
Harry Yeh
Keyword(s):  
Pore Water Pressure ◽  
Initial Conditions ◽  
Scale Effects ◽  
Traditional Approach ◽  
Water Pressure ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Flow Conditions ◽  
The Difference ◽  
The Impact

Study of boulder transport by tsunamis is challenging because boulder size, shape, and composition vary greatly; furthermore, flow conditions, topography, and initial conditions are generally unknown. To investigate the mechanism of boulder pickup, experiments of tsunami-like flow past spherical boulders partially buried in a sediment bed are conducted. The experiments are performed in a large centrifuge facility to reduce scale effects and the corresponding dynamic similitude is discussed. The traditional approach to determine boulder pickup is adapted for the case of a half-buried spherical boulder. The adapted model predicts that the boulders are transported, but does not accurately predict the timing of pick up. To investigate the difference in pickup timing, two physical phenomena are discussed: pore-water-pressure dissipation in the soil, and the impact of the free-surface flow on hydrodynamic forces. For a spherical shaped boulder, vertical forces (i.e. buoyant and lift forces) are critical for the initiation of boulder pickup. It was found that spherical boulders that are three-quarter buried in the soil are not transported, even when exposed to flow conditions that would otherwise predict transport.

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