Circular Piers Research Articles

Effect of Soil Non-Uniformity on Scour for Circular Compound Bridge Piers

Bridge piers having a varying foundation diameter are known as compound bridge piers. In India for the construction of road and railway bridges circular compound bridge piers are mostly adopted. In past studies it has been concluded that 60-70% of bridge failure occurs because of scour around bridge pier across a river due to flowing water. Most of the past studies were done on the uniform bridge pier and a very few studies has been carried out so far on scour around compound bridge piers. For economical design of bridge pier foundation there is a need to determine the scour depth. In the present study, an experimental investigation has been carried out for computation of time variant change of scour depth for two different models of circular compound bridge piers over non-uniform soil for all possible cases of position of footing with respect to level of the bed, i.e., I. Footing at the level of bed, and II. Footing below the level of bed (1cm, 2cm, 3cm and 4cm) for non-uniform sediments

Turbulent Flow Structures and Scour Hole Characteristics around Circular Bridge Piers over Non-Uniform Sand Bed Channels with Downward Seepage

In alluvial rivers bridge piers often cause local scour, a complex phenomenon as a result of the interaction between turbulent flow and bed material. In this paper, the results of an experimental study on the scour hole characteristics around single vertical pier sets on a non-uniform sand bed, under no seepage, and with downward seepage conditions, are described. In case of downward seepage, turbulent statistics, such as Reynolds stress, higher order moments, TKE-flux, and consequently sediment transport, decrease upstream of the pier, while increasing on both sides of it, where the enhanced erosive capacity of the flow results in an increase in the scour hole width. Moreover, the scour hole length shifts downstream. Empirical equations for the evaluation of scour hole characteristics, such as the length, width, area, and volume, including the downward seepage parameter, are proposed and experimentally tested. Model predictions give reasonably good agreement with the experimental data.

ANN optimized by PSO and Firefly algorithms for predicting scour depths around bridge piers

The estimation of scour depths is extremely important in designing the foundation of piers which ensure the integrity of bridges and other hydraulic structures. Complicated hydrodynamic processes around piers are the main challenge to formulate explicitly empirical equations in providing scour depth estimation. Consequently, the proposed empirical formulae only yield good prediction results for specific conditions. In this study, the particle swarm optimization and Firefly algorithms are proposed to optimize artificial neural network (ANN) models to improve predicting the scour depths around circular piers at the equilibrium stage. The results of the proposed modelling frameworks are compared with an ANN network trained by the Levenberg–Marquardt (LM) algorithm which was widely adopted in the literature for prediction purposes. The predicted results exhibit that the equilibrium maximum scouring depths derived from our proposed models are better compared to the values from empirical models and the single ANN model trained by LM. Our study implicates that the new model frameworks could successfully replace the traditional methods, and more applications of these frameworks on computational fluid mechanics and hydraulic structure designs should be considered.

Local Scour of Armor Layer Processes around the Circular Pier in Non-Uniform Gravel Bed

Flume experiments have been carried out under clear water scour conditions to analyze the maximum equilibrium scour depth and scour processes in armored streambeds. A total of 85 experiments have been carried out using different diameters of circular piers and non-uniform gravels. A graphical approach for dimensionless scour depth in equilibrium condition around the circular pier in armored streambeds has been developed. As per this curve, the maximum dimensionless scour depth variation with dimensionless armor particle size depends on the densimetric particle Froude number (Frd50), and the decreasing rate of dimensionless scour depth decreases with the value of Frd50.

Blast Load Mitigation of Concrete Bridge Circular Piers by External Strengthening of Pier

Blast Load Mitigation of Concrete Bridge Circular Piers by External Strengthening of Pier

Downward seepage effects on dynamics of scour depth and migrating dune-like bedforms at tandem piers

The present study focuses on multi-scale statistical characterization of scour depth at tandem piers and migrating dune-like bedforms forming behind the piers in downward seepage affected alluvial channel, using an experimental approach. Experiments were conducted using two circular piers arranged in a tandem manner for no seepage, 10% seepage, and 15% seepage condition. The erosive capacity of reversal flow is hindered with downward seepage, which results in reducing velocity and Reynolds stress near the bed at upstream of piers in case of seepage runs. The bed elevation of the scoured region is decreasing with the increasing seepage percentage and the growth in scour depth is diminishing with time. The celerity of scour depth is decreasing with time as well as decreasing with increasing downward seepage. Probability density function of bedform elevation has positive tail slightly thicker than the Gaussian.

Live-Bed Scour at Wide and Long-Skewed Bridge Piers in Comparatively Shallow Water

An investigation of the characteristics of live-bed scour at circular and skewed rectangular (slab) piers in comparatively shallow flows is presented. The 110 experiments were undertaken in a 2.4-m flume using two circular piers and a slab (long) pier. Based on flow shallowness, that is, the ratio of approaching flow depth (y0) to pier diameter (D), the new data span the wide-pier (y0/D<0.2) and transition-pier (0.2≤y0/D<1.4) scour ranges. The Sheppard-Melville (S-M) method shows better performance than the other existing predictors and is more readily modified. Modification to the equation for the flow shallowness factor in the S-M method is proposed, based on both the data from the present study and those from literature. The results show the considerable influence of flow shallowness ratio on scour depth at piers in comparatively shallow water, and that, even for non–ripple-forming sediment, the scour depth at the live-bed peak may still exceed that at the clear-water threshold. The modified predictor provides better accuracy than the original Sheppard-Melville method for piers with y0/D<1, and no significant underestimation of the maximum scour depth is observed.

Developing empirical formulas for assessing the scour of vertical and inclined piers

Because scour is one of the main reasons for bridge failure, this study focuses on accurately predicting the maximum scour depth around different vertical and inclined piers. Scouring is an issue of concern in the bridge design process, as most existing equations for predicting local scour near bridge piers suffer from over- or underprediction issues, resulting in higher foundation costs or bridge failure and inaccurate predictions of the scour around piers. The dimensionless maximum scour depths (ys/D) of vertical and inclined piers were investigated for seven pier shapes with different L/D ratios and four inclination angles (θ) under shallow flow conditions. The inclined pier configuration reduced the ys/D of the piers. The maximum ys/D was observed for a rectangular pier with an L/D of 4.5 in both vertical and inclined configurations (θ of 10, 15 and 21°, respectively). The ys/D was significantly decreased by increasing the angle of the pier from 10 to 30°. The ys/D of the inclined rectangular piers decreased as θ decreased from 30 to 10° and the L/D ratio increased from 1 to 4.5. The best ys/D results were obtained for inclined rectangular piers at a θ value of 30° and an L/D ratio of 7.5 compared to other shapes and inclination angles. New equations were developed to predict the local scour depth for circular, square and rectangular bridge piers. The equations yielded excellent results for predicting the maximum clear water scour depth around vertical and inclined piers with inclination angles of 10, 15, 21 and 30°, respectively.

On the Local Scour Around Group Piers in Series by Experimental Tests

In this article a physical model is presented. A trapezoidal shape of channel with 1.45 m width, 1 meter depth and banks slope of 1H: 1.5V was applied. Circular piers (6, 8 and 10cm diameter) were examined under three dissimilar flow discharges of 50, 65 and 80 lit/s and three different median bed material sizes equal to 0.94, 1.31 and 2.12 mm. Seven different longitude distance to pier diameter ratios (1, 1.5, 2, 2.5, 3, 4 and 5) were examined. Measurement of scour depth (upstream, around and downstream of pier) was accomplished in 10, 15, 20, 30, 60, 120, 240 and 360 minutes from the beginning of each examination. The results indicated that 30%-40%, up to 65% and more than 90% of local scour occurs at first two, 10, 120 and 200 minutes from the beginning of test respectively. The effect of dissimilar parameter especially the distance between piers on scour depth at group piers in series was evaluated and the results were compared to other researchers. It was found that our results is best fitted with the general form of well known Sheppard et al. (2004)’s equation.

Numerical modeling of flow around a pier mounted in a flat and fixed bed

Local scour around bridge piers is one of the main causes of bridge failures. Study of local scour is very significant for the safe design of piers and other civil and marine structures. Despite the subject has been explored for many decades, the numerical developments have been very limited due to the complicated interaction of three-dimensional flow, sediment transport and fluid-particle interaction. In this work, a numerical model based upon the Reynolds Average Navier Stokes Equation (k-ε) approach has been used for predicting the three dimensional flow (3D) around a bridge piers (square and cylinder piers), mounted on a flat and fixed bed. The main aim of this paper is the validation of the numerical model, based upon the previous experimental data. The CFD-numerical tool is proficient to qualitatively reproduce the flow characteristic for different pier shape and features around the pier, such as the upstream vortex (horseshoe vortex) and downstream vortex (vortex shedding in the wake). The outcome of this study can be used developing adequate numerical model to simulate the 2D and 3D turbulent flow past the square and circular piers, which are relevant case-studies for the marine and civil structures supported by pillars. The corresponding numerical results are in good agreement with those extracted from available experimental data.

Experimental Study for Protection of Piers Against Local Scour Using Slots

The most important causes of bridge failure are local scour. In this study, laboratory experiments were conducted to investigate the effectiveness of slot as a protection device in reduction of depth of scour at cylindrical piers under clear water flow conditions. The development time of scour depth at the circular pier with and without a slot as a protection device was conducted. The experiments focused on the effect of using different lengths of slot, calculating efficiency and deriving a suitable equation. It was observed that the scour depth decreases as the size of slot length increases; and also the maximum reduction in scour depth equals to 49%. The technique of dimensional analysis was used, and based on laboratory results an empirical formula was derived by using IBM SPSS statistics v24 software. The coefficient of determination (R²) was determined to be (0.961), There was a good agreement between the predicated and observed data.

Influence of steel jacket thickness on the RC bridges’ seismic vulnerability

Abstract The seismic demands of bridges subjected to strong earthquakes are mostly concentrated on piers. The main objective of this study is to assess the seismic vulnerability of retrofitted bridges with steel jackets. It analyzes the influence of the steel jacket thickness on the seismic capacity and demand of bridges. The bridges in study have two simple supported spans with superstructure composed by AASHTO type girders and a substructure formed with one circular pier over a stiff foundation. They are located on the Pacific coast of Mexico that is a zone of high seismicity. The bridges seismic capacity are evaluated through nonlinear static analyses and the shear force and displacement demands were determined using capacity spectra with a group of 10 real accelerograms from a subduction source. The response spectra were scaled to several peak ground accelerations (PGA) with the aim to estimate four damage scenarios linked each one to a probability of exceedance in a specific period, for return periods in the range of 72–3500 years that represent service level and maximum considered earthquake. Results show that the confining effect provided by the steel jackets substantially improves the seismic performance of the bridges piers. The increase of jacket thickness guides to important increments on columns base shear capacity, and the influence of the steel jacket thickness depends on the limit state and bridge slenderness ratio.

Local scour around closely placed bridge piers

ABSTRACT Bridges situated close to each other show interference effect on scour depth around bridge elements as compared to the scour depth around isolated bridge elements. A number of investigations have been made in case of a single isolated pier having different shapes and flow conditions. But the investigations on bridges likely to interfere are relatively much lesser. Addressing the issue, an experimental study was conducted with circular and oblong piers of size, D = 6.2 cm forming tandem, side by side and staggered patterns. A recirculating flume 12 m long, 0.6 m wide and 0.7 m high with uniform sized sediment of average size, d5 0 = 0.23 mm was used for the experimental work. Experiments were run at a velocity equal to 0.93 times the critical velocity, uc. Piers when spaced from each other by a distance of one pier diameter showed maximum scour depths of 1.06, 1.51 and 1.53, respectively, for the tandem, side by side and staggered arrangements as compared to that of a single pier. However, when the inter- pier spacing was 16 times for tandem, two times for side by side and five times for staggered arrangements, the piers behaved independent of each other’s presence.

Interaction between channel junction and bridge pier on flow characteristics

Considering many bridge piers that destroyed every year due to scouring, flow behavior around these obstructions was one of the interests of engineers in recent years. This phenomenon has usually been studied in straight channels and has rarely studied at channel confluences. To accomplish this, after calibrating SSIIM1 model for a 90° channel junction, the effect of circular bridge pier at two positions after channel confluence (x/w = −1.5 and x/w = −3, x = distance from upstream corner of junction in flow direction, w = main channel width) on flow pattern were conducted. The results indicated that bridge pier caused backwater rise by 4.1% at upstream of channel confluence compared to without bridge pier case. Water surface profile of main channel reduced in two steps. First step was due to reduction of effective width of main channel because of tributary channel inflow and the second one was due to flow contraction near bridge pier while in the absence of bridge pier it only had one step. Also the results showed that longitudinal velocity decreased at upstream sections of bridge pier. At the centerline of the section corresponding to downstream corner of junction for (x/w = −1.5) and (x/w = −3) these reductions were 25.4% and 16.3% respectively.

Proposed Input Energy-Based Damage Index for RC Bridge Piers

In this paper, a new damage index is proposed for RC bridge piers using the concept of earthquake input energy distribution in a structural system. The damage index was defined as the ratio of the hysteretic energy to the earthquake input energy to take into account the cumulative effects of stiffness degradation, inelastic deformation, and material nonlinearities throughout the loading history. A damage-assessment method was also developed in accordance with material strain. For this purpose, a set of circular RC bridge piers tested under cyclic/seismic loadings was simulated to calibrate the reliability of the proposed damage index and strain-based damage limit states. The results confirmed the ability of the damage index to predict the damage levels of piers under cyclic and seismic loading. The damage index was also compared to some existing damage indices. The comparison showed that the proposed damage index is a relatively simple and practical approach that can provide a reasonably gradual progression of damage throughout the loading history more convincingly than other damage models.

Experimental Study on Scour at a Sharp-Nose Bridge Pier with Debris Blockage

AbstractPrevious experimental research on the effects of debris on pier scour has focused primarily on circular and rectangular piers with debris present just under flow free surface. Debris-induce...

Characterization of horseshoe vortex in a developing scour hole at a cylindrical bridge pier

Since local scour at bridge piers in rivers and estuaries is a major cause of bridge failure, estimation of the maximum local scour depth is of great importance to hydraulic and coastal engineers. Although numerous studies that focus on scour-depth prediction have been done and published, understanding of the flow and turbulence characteristics of the horseshoe vortex that drives the scour mechanism in a developing scour hole still is immature. This study aims to quantify the detailed turbulent flow field in a developing clear-water scour hole at a circular pier using Particle Image Velocimetry (PIV). The distributions of velocity fields, turbulence intensities, and Reynolds shear stresses of the horseshoe vortex that form in front of the pier at different scour stages (t = 0, 0.5, 1, 12, 24, and 48 h) are presented in this paper. During scour development, the horseshoe vortex system was found to evolve from one initially small vortex to three vortices. The strength and size of the main vortex are found to increase with increasing scour depth. The regions of both the maximum turbulence intensity and Reynolds shear stress are found to form at a location upstream of the main vortex, where the large turbulent eddies have the highest possibility of occurrence. Results from this study not only provide new insight into the complex flow-sediment interaction at bridge piers, but also provide valuable experimental databases for advanced numerical simulations.

Scour around Bridge Piers: Numerical Investigations of the Longitudinal Biconcave Pier Shape

The flow pattern around a bridge pier and the scouring phenomenon are very complicated. The basic mechanism causing local scour is the down-flow at the upstream face of the pier. It is understood that the horseshoe vortex is the key mechanism that leads to the local scour around pier; existing literature revealed that the strength of the down-flow, horseshoe vortex and the wake vortex are greater in the case of square piers compared to circular piers. In this paper we have investigated a new longitudinal biconcave bridge pier shape that reduces better the bed shear stress. For that purpose, a number of numerical simulations have been carried out using a Finite Volume Method (FVM) and for the turbulence model we have chosen the Detached Eddy Simulation (DES) for its capability to capture the rich dynamics of the horseshoe vortex at the upstream junction between the pier and the bed.The present study shows that the new longitudinal biconcave bridge pier shape reduces 10 % to 12 % the bed shear stress at the junction between the pier and the bed in other hand this shape increases the bed shear stress about 20 % but at a distance of D downstream the bridge pier in the flow direction.

Numerical Study of Damage Modes and Assessment of Circular RC Pier under Noncontact Explosions

Numerical Study of Damage Modes and Assessment of Circular RC Pier under Noncontact Explosions

Hydromorphological Numerical Model of the Local Scour Process Around Bridge Piers

The aim of this study was to assess the simulation and prediction of scour processes, both hydrodynamically and morphologically, around vertical and inclined piers. A new version of FLOW-3D v. 11.2, including three sediment transport equations, was extensively used for estimating the scour around the pier. The results of the model in terms of water surface, flow velocity, bed shear stress and scour depth were effectively compared with several sets of the experimental and numerical data in the literature. The model provided an accurate estimation of water surface, flow velocity and bed shear stress. However, the results for the vertical velocity upstream of the pier were underestimated. The predictive capabilities of the model were mainly dependent on the pier shape and inclined direction. The downflow, stream-wise velocity, shear stress and local scour depth were significantly reduced at the inclination angle of the circular pier downstream. However, they were nearly equal to those of an inclined perpendicular circular pier. This study strongly demonstrates that a 3D hydromorphological model can be effectively used to predict the scour depth around piers.