scholarly journals Effect of Scour on the Natural Frequency Responses of Bridge Piers: Development of a Scour Depth Sensor

2019 ◽  
Vol 4 (2) ◽  
pp. 21 ◽  
Author(s):  
Nissrine Boujia ◽  
Franziska Schmidt ◽  
Christophe Chevalier ◽  
Dominique Siegert ◽  
Damien Pham van Bang
Keyword(s):  
Laboratory Tests ◽  
Continuous Monitoring ◽  
Clayey Soil ◽  
Element Model ◽  
Bridge Piers ◽  
Scour Depth ◽  
Depth Sensor ◽  
Bridge Foundations ◽  
Frequency Responses ◽  
Second Category

Local scour is the removal of soil around bridge foundations under the erosive action of flowing water. This hydraulic risk has raised awareness of the need for developing continuous monitoring techniques to estimate scour depth around bridge piers and abutments. One of the emerging techniques is based on monitoring the vibration frequency of either bridge piers or a driven sensor in the riverbed. The sensor proposed in this study falls into the second category. Some unresolved issues are investigated: the effect of the geometry and material of the sensor, the effect of the embedded length and the effect of soil type. To this end, extensive laboratory tests are performed using rods of different materials, with various geometries and lengths. These tests are conducted in both dry sand and a soft clayey soil. Since the sensor will be placed in the riverbed, it is crucial to evaluate the effect of immersed conditions on its response. A numerical 3D finite-element model was developed and compared against experimental data. This model was then used to compute the ‘wet’ frequencies of the sensor. Finally, based on both the experimental and numerical results, an equivalent cantilever model is proposed to correlate the variation of the frequency of the sensor to the scour depth.

UAV Based Multi-Hazard Vulnerability Assessment System for Bridges Exposed to Scour

2020 ◽  
Author(s):  
Okan Özcan ◽  
Orkan Özcan
Keyword(s):  
Load Capacity ◽  
Time History ◽  
Element Model ◽  
Lateral Load ◽  
Assessment System ◽  
Bridge Piers ◽  
Scour Depth ◽  
River Bed ◽  
Principal Axes

<p>Evaluating the multi-hazard performance of river crossing bridges under probable earthquake, flood, and scouring scenarios is a cumbersome task in performance-based engineering. The loss of lateral load capacity at bridge foundations may induce bridges to become highly vulnerable to failure when the effects of scour and floods are combined. Besides, the assessment of local scouring mechanism around bridge piers provides information for decision‐making regarding the pile footing design and for predicting the safety of bridges under critical scoured conditions. Thereby, accurate high-resolution Digital Elevation Models (DEMs) are critical for many hydraulic applications such as erosion, hydraulic modelling, sediment transport, and morphodynamics. In the present study, an automated unmanned aerial vehicle (UAV) based multi-hazard performance assessment system was developed to respond to rapid performance evaluation and performance prediction needs for river crossing reinforced concrete (RC) bridges. The Bogacay Bridge constructed over Bogacay in Antalya, Turkey was selected as the case study. In the developed system, firstly the seasonally acquired UAV measurements were used to obtain the DEMs of the river bed from 2016 to 2019. The transverse cross sections of the river bed that were taken close to the inspected bridge were used to measure the depth of the scoured regions along the bridge piles under the present conditions. Separately, in conjunction with the flood simulation and validation with 2003 flood event (corresponds to Q<sub>50</sub>=1940 m<sup>3</sup>/s), the scour depth after maximum probable flood load according to the return period of 500 years (Q<sub>500</sub>=2560 m<sup>3</sup>/s) were predicted by HEC-RAS software. Afterwards, the 3D finite element model (FEM) of the bridge was constituted automatically with the developed code considering the scoured piles. The flood loads were exerted on the modeled bridge with regard to the HEC-RAS flood inundation map and relevant water depth estimations around the bridge piers. For the seismic evaluation, nonlinear time history analyses (THA) were conducted by using scaled eleven scaled earthquake acceleration records that were acting in both principal axes of the bridge simultaneously by considering maximum direction spectra (SaRotD100) as compatible with the region seismicity. In the analyses; as the scour depth increased, the fundamental periods, shear forces and the bending moments were observed to increase while the pile lateral load capacities diminished. Therefore, the applicability of the proposed system was verified using the case study bridge.</p>

Experimental Investigation of Local Scour Around Conical Pier

2011 ◽  
Author(s):  
Masoumeh Pourahmadi ◽  
Habib Hakimzadeh
Keyword(s):  
Reduction Rate ◽  
Bridge Piers ◽  
Geometric Standard Deviation ◽  
Scour Depth ◽  
Indirect Methods ◽  
Indirect Control ◽  
Scour Protection ◽  
Second Category ◽  
Direct And Indirect Methods ◽  
Key Parameter

There are many reports about failure of bridges around the world due to scouring. This shows the importance of research on scouring and any possibility on scour protection. The method used of control of scouring around the bridge piers can be divided in two categories, namely: Direct and Indirect methods. The first method may be done by increasing the streambed resistance. This is usually done by riprap around piers. Indirect control, however, can be achieved by changing the flow pattern around a pier. The second method can be done for instance by using a collar around the pier or using a slot within the pier. Another method of the second category is to use variable section in depth. For this purpose, various slopes of conical piers are investigated in this research study. Experiments were carried out in a channel with 10 meters long, 0.3 meter wide and 0.5 meter depth, having a horizontal slope. Median size of sediment was 0.78 mm with geometric standard deviation of 1.24. The experimental results have been shown that the scour depth at conical piers decrease in compare with cylindrical ones. These observations, may partly be due to decrease in bed shear stress, which is a key parameter for the sediment transport. Therefore, from experimental data it was found that with a very mild slope on conical pier, the scour depth decreased about 15.8% when compared with the cylindrical one. For the other piers with larger slope and larger diameter on the bed, the wall side effects were appeared, however the reduction rate of scour depth was not as much as expected, compared with the first conical pier.

Evaluation of Selected Pier-Scour Equations Using Field Data

1996 ◽  
Vol 1523 (1) ◽  
pp. 186-195 ◽  
Author(s):  
Mark N. Landers ◽  
David S. Mueller
Keyword(s):  
Field Measurements ◽  
Bridge Piers ◽  
Critical Ratio ◽  
Scour Depth ◽  
Flow Depth ◽  
Clear Water ◽  
Pier Scour ◽  
Logarithmic Space ◽  
State Highway ◽  
Federal Highway

Field measurements of channel scour at bridges are needed to improve the understanding of scour processes and the ability to accurately predict scour depths. An extensive data base of pier-scour measurements has been developed over the last several years in cooperative studies between state highway departments, the Federal Highway Administration, and the U.S. Geological Survey. Selected scour processes and scour design equations are evaluated using 139 measurements of local scour in live-bed and clear-water conditions. Pier-scour measurements were made at 44 bridges around 90 bridge piers in 12 states. The influence of pier width on scour depth is linear in logarithmic space. The maximum observed ratio of pier width to scour depth is 2.1 for piers aligned to the flow. Flow depth and scour depth were found to have a relation that is linear in logarithmic space and that is not bounded by some critical ratio of flow depth to pier width. Comparisons of computed and observed scour depths indicate that none of the selected equations accurately estimate the depth of scour for all of the measured conditions. Some of the equations performed well as conservative design equations; however, they overpredict many observed scour depths by large amounts. Some equations fit the data well for observed scour depths less than about 3 m (9.8 ft), but significantly underpredict larger observed scour depths.

scholarly journals Analysis of Scour Depth Around Bridge Piers With Round Nose Shape by HEC-RAS 5.0.7 Software

2021 ◽  
Vol 1764 (1) ◽  
pp. 012151
Author(s):  
C S Silvia ◽  
M Ikhsan ◽  
A Wirayuda ◽  
Mastiar
Keyword(s):  
Bridge Piers ◽  
Scour Depth ◽  
Nose Shape

scholarly journals Hybrid Scour Depth Prediction Equations for Reliable Design of Bridge Piers

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2019
Author(s):  
Hossein Hamidifar ◽  
Faezeh Zanganeh-Inaloo ◽  
Iacopo Carnacina
Keyword(s):  
Flow Velocity ◽  
Critical Velocity ◽  
Depth Estimation ◽  
Hybrid Models ◽  
Velocity Estimation ◽  
Bridge Piers ◽  
Critical Flow ◽  
Scour Depth ◽  
Critical Flow Velocity ◽  
Estimation Equations

Numerous models have been proposed in the past to predict the maximum scour depth around bridge piers. These studies have all focused on the different parameters that could affect the maximum scour depth and the model accuracy. One of the main parameters individuated is the critical velocity of the approaching flow. The present study aimed at investigating the effect of different equations to determine the critical flow velocity on the accuracy of models for estimating the maximum scour depth around bridge piers. Here, 10 scour depth estimation equations, which include the critical flow velocity as one of the influencing parameters, and 8 critical velocity estimation equations were examined, for a total combination of 80 hybrid models. In addition, a sensitivity analysis of the selected scour depth equations to the critical velocity was investigated. The results of the selected models were compared with experimental data, and the best hybrid models were identified using statistical indicators. The accuracy of the best models, including YJAF-VRAD, YJAF-VARN, and YJAI-VRAD models, was also evaluated using field data available in the literature. Finally, correction factors were implied to the selected models to increase their accuracy in predicting the maximum scour depth.

scholarly journals Comparison between the circular and square collar in reduction of local scouring around bridge piers

2018 ◽  
Vol 40 ◽  
pp. 03002 ◽  
Author(s):  
Saeed Reza Khodashenas ◽  
Hossain Shariati ◽  
Kazem Esmaeeli
Keyword(s):  
Bridge Piers ◽  
Scour Depth ◽  
Circular Shape ◽  
Level Elevation

In this study operation of two types of circular and square collars has been investigated on a single cylindrical pier. The results showed that using of these two types of collars cause to reduction of scour depth especially under the bed level (elevation). This research showed that the square collar is more effective than circular shape in decreasing of the scour depth). The square and circular collars showed 70% and 50% decrease in rate of scour depth, respectively in compared with simple pier without collar.

scholarly journals Nose-Angle Bridge Piers as Alternative Countermeasures for Local Scour Reduction

2018 ◽  
Vol 13 (2) ◽  
pp. 110-120 ◽  
Author(s):  
Ibtesam Abudallah Habib ◽  
Wan Hanna Melini Wan Mohtar ◽  
Atef Elsaiad ◽  
Ahmed El-Shafie
Keyword(s):  
Froude Number ◽  
Local Scour ◽  
Bridge Piers ◽  
Scour Depth ◽  
Skew Angle ◽  
Flow Angle ◽  
Sediment Size ◽  
Low Froude Number ◽  
Skew Angles ◽  
Depth Reduction

This study investigates the performance nose-angle piers as countermeasures for local scour reduction around piers. Four nose angles were studied, i.e., 90°, 70°, 60° and 45° and tested in a laboratory. The sediment size was fixed at 0.39 mm whereas the flow angle of attack (or skew angle) was varied at four angles, i.e., skew angles, i.e., 0°, 10°, 20° and 30°. Scour reduction was clear when decreasing nose angles and reached maximum when the nose angle is 45°. Increasing the flow velocity and skew angle was subsequently increasing the scour profile, both in vertical and transversal directions. However, the efficiency of nose angle piers was only high at low Froude number less than 0.40 where higher Froude number gives minimal changes in the maximum scour depth reduction. At a higher skew angle, although showed promising maximum scour depth reduction, the increasing pier projected width resulted in the increase of transversal lengths.

scholarly journals Analysis of Water Flow Pressure on Bridge Piers considering the Impact Effect

2015 ◽  
Vol 2015 ◽  
pp. 1-8
Author(s):  
Yin-hui Wang ◽  
Yi-song Zou ◽  
Lue-qin Xu ◽  
Zheng Luo
Keyword(s):  
Water Flow ◽  
Coupling Effect ◽  
Highway Bridges ◽  
Element Model ◽  
Bridge Pier ◽  
Bridge Piers ◽  
Water Current ◽  
Fluid Structure ◽  
Impact Effect ◽  
The Impact

In order to investigate the effects of water current impact and fluid-structure interaction on the bridge piers, the mechanism of water flow impact on the bridge pier is firstly studied. Then a finite element model of a bridge pier is established including the effects of water flow impact as well as the water circumferential motion around the pier. Comparative study is conducted between the results of water impact effect, fluid-structure coupling effect, theoretical analysis, and also the results derived using the formulas specified in the design codes home and abroad. The results show that the water flow force calculated using the formulas provided by the codes should be multiplied by an impact amplifier to account for the effect of flood impact on the bridge pier. When the flood flows around the pier, the fluid-structure coupling effect on the bridge pier can be neglected. The method specified in the China guidelines ofGeneral Code for Design of Highway Bridges and Culvertstends to provide a larger result of the water flow force.

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