Circular Piers Research Articles

Reduction of scour around circular piers

In this paper new protection methods that allow reducing the local scour around bridge circular piers are proposed. The effect produced by the placing of collars around a circular pier of 7.3 cm diameter on the scour was analyzed. Initially a concentric collar and other eccentric were used. These were placed separately around the pier at the bed level. Experiments, by device, were made, maintaining the flow conditions used in the reference experiments. Then, experiments that consisted in combining two collars, one at the bed level and other to certain distance above the bed were carried out. Moreover, the effect produced by the elevation of the eccentric collar with regard to the bed on the scour depth was studied. Subsequently, it was proposed to diminish the piers local scour using a vertical wall perpendicular to flow, upstream of the pier. For each experiment, the space among the pier and the vertical wall was varied. It was studied the effect produced by the size of the vertical wall, by varying the width. For each experiment, the scoured bed profile was measured. This allowed determining the maximum scour depth. It was found that devices employed reduce reasonably well the local scour depth.

Experimental investigation of local scour around circular bridge piers under steady state flow conditions

Local scour around bridge piers is one of the main causes of bridge failures. In this study, scour depths and scour hole geometries around circular bridge piers were investigated under clear water scour conditions for various flow rates. The experiments were carried out in a rectangular flume 80 cm wide, 18.6 m long and 75 cm high by using uniform sediment with a median diameter of 1.63 mm and geometric standard deviation of 1.3. The flow rates and approach flow depths were measured with an electromagnetic flow meter and ultrasonic level sensors, respectively. A new empirical equation for the determination of scour depth is proposed based on the experimental findings of the present study and on experimental data available in the literature. The experimental results were also compared with those calculated using several empirical equations developed by previous studies. The proposed new equation to predict scour depth around a circular bridge pier was evaluated in terms of determination coefficient (R2) and scatter index (SI). The Fisher (f)test was also applied to test the statistical significance of the proposed equation.

Seismic behavior of deficient reinforced concrete bridge piers confined with FRP – A fractional factorial analysis

Material properties, amount of longitudinal and transverse steel, external confinement, axial load and shear span-depth ratio affect the lateral load capacity, ductility and failure mode of retrofitted bridge piers under seismic load. These parameters are considerably different in old reinforced concrete (RC) bridge piers compared to the seismically designed bridges. This research investigates the effects of these factors and their interactions on the limit states of carbon fiber reinforced polymer (CFRP) confined seismically deficient RC circular bridge piers using fractional factorial design method. CFRP-confined bridge piers are modelled using a fiber modelling approach and nonlinear static pushover analyses of the bridge piers are conducted in order to determine the sequence of different limit states such as yielding, buckling and fracture of reinforcement, and concrete crushing along with ductility capacity of the piers. This study shows that the shear span-depth ratio, yield strength and longitudinal reinforcement ratio, axial load and CFRP confinement significantly affect the lateral load capacity, ductility and the failure mode of retrofitted bridge piers under seismic load.

Enhancing PIV image and fractal descriptor for velocity and shear stresses propagation around a circular pier

In this study, the fractal dimensions of velocity fluctuations and the Reynolds shear stresses propagation for flow around a circular bridge pier are presented. In the study reported herein, the fractal dimension of velocity fluctuations (u′, v′, w′) and the Reynolds shear stresses (u′v′ and u′w′) of flow around a bridge pier were computed using a Fractal Interpolation Function (FIF) algorithm. The velocity fluctuations of flow along a horizontal plane above the bed were measured using Acoustic Doppler Velocity meter (ADV) and Particle Image Velocimetry (PIV). The PIV is a powerful technique which enables us to attain high resolution spatial and temporal information of turbulent flow using instantaneous time snapshots. In this study, PIV was used for detection of high resolution fractal scaling around a bridge pier. The results showed that the fractal dimension of flow fluctuated significantly in the longitudinal and transverse directions in the vicinity of the pier. It was also found that the fractal dimension of velocity fluctuations and shear stresses increased rapidly at vicinity of pier at downstream whereas it remained approximately unchanged far downstream of the pier. The higher value of fractal dimension was found at a distance equal to one times of the pier diameter in the back of the pier. Furthermore, the average fractal dimension for the streamwise and transverse velocity fluctuations decreased from the centreline to the side wall of the flume. Finally, the results from ADV measurement were consistent with the result from PIV, therefore, the ADV enables to detect turbulent characteristics of flow around a circular bridge pier.

Reducing local scour at bridge piers using an upstream subsidiary triangular pillar

The objective of this experimental study was to examine the effect of an upstream subsidiary triangular pillar on the development of local scour at a single circular bridge pier. The triangular pillar was placed such that its apex faced the approach flow and its base length was equal to the pier diameter (D) in all experiments. The experiments were conducted to investigate the effect of the spacing between the base of the subsidiary pillar and the bridge pier (S) and the apex angle (α) of the triangular pillar on the dimensions of the scour hole and its temporal development at different Froude numbers. The experiments were conducted in a rectangular flume under clear-water scour conditions at Froude number ranging between 0.1 and 0.3. Relative spacing (S/D) of 0, 0.5, 1, 1.5, 2, and 3, as well as apex angle (α) of 60°, 90° and 120° were tested. The results show that the maximum scour depth at the pier could be minimized using three different combinations of spacing and apex angle. The highest reduction in the maximum scour depth (dsm) of approximately 28 % was possible using S/D of 3 and α of 90° compared to the pier-alone case. Overall the performance of the 90° apex angle pillar surpassed the other two angles.

Dynamic responses of concrete piers under close-in blast loading

Piers are essential components for bridge structures while exposed directly to car-bombed detonation. Numerical simulation and failure-mode investigation are conducted for concrete piers under close-in blast loading to better understand their dynamic responses. The effects of pier geometry, reinforcement arrangement, and location of detonation are particularly studied on the horizontal velocity and displacement of the pier base. The results demonstrate that circular piers provide more effective blast resistance than square piers under the same blast circumstance. Failure modes for concrete piers are determined by the longitudinal rebar arrangement, which contributes to the major part of shear capacity of the pier base when subjected to close-in blast loading. While the hoop effect is limited for blast resistance of piers, the restraining influence of the ground is significant with respect to the pier base, and performance-based seismic design concept such as plastic-hinges can be employed at the base of concrete piers for anti-blast design.

Scaling Analysis of Pier-Scouring Processes

AbstractThis study presents a scaling analysis of the time development of clear-water scour depth at bridge piers. It shows that the widely-used exponential formula can be theoretically derived with scaling arguments. The derivation provides connections between the physical pier-scouring process and two empirical constants used in the formula. The dependence of the two constants on sediment coarseness is calibrated using published laboratory data with scour duration ranging from 49 to 1094 h. The analysis presented is restricted to conditions, including steady flow, clear-water scour, narrow circular cylindrical pier, and uniform sediment with low coarseness.

The effect of circular bridge piers with different inclination angles toward downstream on scour

A fundamental principle in the safe design of bridge piers is to estimate maximum scour depth. As such, many researchers devoted their efforts to study the phenomenon of scour around bridge piers and to present relationships to estimate maximum scour depth. In the current research, scour around circular bridge piers with two different diameters and different inclination angles toward downstream has been investigated experimentally under clear water and different discharges. The obtained results revealed that increase in the inclination angle leads to a significant decrease in the scour depth, dimensions of sediment ridge and scour hole. Moreover, by comparing the data obtained from vertical bridge pier and well-known relationships, a relationship having the most agreement with the results was selected and modified to estimate equilibrium scour depth around inclined piers.

Scour Formation Due to Laterally Inclined Circular Pier

The purpose of this paper was to study the local scour formation due to an inclined circular bridge pier. The experiments for two cases of inclined and vertical piers under clear-water condition with four different flow conditions have been performed. The experiments were conducted in the hydraulic laboratory of Tarbiat Modares University in a rectangular channel. Also, for better interpretation of the observed changes, the longitudinal component values of the velocity in a vertical plain with definite distance located downstream of the vertical and inclined piers were recorded using a velocimeter. The results show that although the scour hole shape and its ridge is changed with the inclination angle of pier, the maximum scour depth in a laterally inclined pier is almost equal to that of a vertical pier and the location of the maximum scour depth in vertical pier has transferred from the 0° area to the approximately 30° area in inclined pier state.

Hybrid simulation of bridge pier uplifting

Substructured Pseudodynamic testing is used to study the transverse seismic response of a bridge with box-girder deck monolithically connected to circular piers, but free to move laterally at the abutments. The tests are of two types, each one with two variants: with the pier footing rocking on elastic soil and uplifting from it, or fixed to rigid ground. The first type concerns a two-span deck connected monolithically to a central pier and supported at each end on the abutment through a pair of elastomeric bearings, which are stiff and strong in compression but very soft and weak in tension. The second one concerns the interior piers of multi-span bridges having all spans equal and all piers similar. The pier was physically tested at 1:2 scale; everything else was numerically simulated online with Opensees. The deck, the soil and the bearings were modeled as elastic, but not allowing tension to develop at the soil-footing interface, and the bearings two orders of magnitude more flexible in tension than in compression. In the first type of tests, at a peak ground acceleration (PGA) of 0.15 g, the footing uplifted, the bearings developed tension, but the pier stayed elastic. In the second type of tests, with a PGA of 0.4 g, uplifting of the footing did not prevent plastic hinging at the pier base, but reduced significantly the pier damage. A cyclic quasi-static test in the end shows the deformation capacity margins of the pier.

Scour control at bridge piers using macro-roughness elements

A new approach involving macro-roughness elements is proposed as a scour countermeasure at circular bridge piers subject to debris accumulation. Experiments were carried out under clear water conditions with the approaching flow velocity set at the threshold of sediment motion. The efficiency of the method was investigated in terms of scour morphology reduction and temporal scour evolution. The results show the effectiveness of the method in reducing maximum scour depth. In some cases, the elements did not reduce the maximum scour depth but were effective in reducing the volume of the scour hole. Based on the experimental data, empirical equations were derived to estimate the temporal local scour depth in the presence of debris accumulation and macro-roughness elements.

Seismic Performance of Natural Fibre Reinforced Polymer-Concrete Bridge Piers

This paper addresses the usage of new construction materials made of natural fibre reinforced polymer and concrete composite for future earthquake-resistant structures. The structure considered is a simple circular bridge pier. To evaluate the seismic performance of the structure shake table experiments were performed. To reveal the consequence of the magnitude of the ground excitation for the structure the effect of a gradual increase of the peak ground displacement is investigated. The results show that although external damage to the structure cannot be observed the bond between polymer and concrete is a significant factor that determines the performance of the structure.

Effects of Oval and Circular Piers on Velocity and Shear Stress Changes by Using Open FOAM Software

Effects of Oval and Circular Piers on Velocity and Shear Stress Changes by Using Open FOAM Software

Experimental and finite element investigation of strengthened LSC bridge piers under Quasi-Static Cyclic Load Test

Mostly bridges failures due to earthquake are the result of inadequate seismic design of piers. Another reason includes the use of Low Strength Concrete (LSC) in developing countries. One of the emerging and popular techniques of rehabilitating structure includes retrofitting with Fiber Reinforced Polymers (FRP’s). In order to investigate the effectiveness of jacketing with Carbon Fiber Reinforced Polymers (CFRP) towards improvement in strength, ductility and other dynamic properties, four scaled down (1:4) LSC circular bridge pier models were first strengthened with CFRP wraps and then subjected to Quasi-Static Cyclic Load Tests (QSCLT) and Free Vibration Tests (FVT). The bridge pier models were later analyzed using finite element software i.e. Seismostruct and the results were compared with the experimentally tested results in terms of energy dissipation capacity of retrofitted bridge piers. The external confinement by CFRP’s enhanced their energy dissipation capabilities and hence strength and ductility of the reinforced concrete piers.

Circulation characteristics of horseshoe vortex in scour region around circular piers

This paper presents an experimental investigation of the circulation of the horseshoe vortex system within the equilibrium scour hole at a circular pier, with the data measured by an acoustic Doppler velocimeter (ADV). Velocity vector plots and vorticity contours of the flow field on the upstream plane of symmetry (y = 0 cm) and on the planes ±3 cm away from the plane of symmetry (y = ±3 cm) are presented. The vorticity and circulation of the horseshoe vortices were determined using the forward difference technique and Stokes theorem, respectively. The results show that the magnitudes of circulations are similar on the planes y = 3 cm and y = −3 cm, which are less than those on the plane y = 0 cm. The circulation decreases with the increase of flow shallowness, and increases with the densimetric Froude number. It also increases with the pier Reynolds number at a constant densimetric Froude number, or at a constant flow shallowness. The relative vortex strength (dimensionless circulation) decreases with the increase of the pier Reynolds number. Some empirical equations are proposed based on the results. The predicted circulation values with these equations match the measured data, which indicates that these equations can be used to estimate the circulation in future studies.

Effect of Bridge Pier Position on Scour Reduction According to Flow Direction

An experimental approach was conducted to study the effect of the change in the position of bridge pier on scour reduction with respect to flow direction. The experiments included the study of new method to reduce scour depth in front of bridge pier by changing the position of bridge pier (named after here as downstream facing round-nosed bridge pier). The down flow deflected away from the front of the opposite pier, and the vortex becomes small and does not affect the pier. In this study, three piers—circular 10 cm, upstream facing round-nosed (10–4) cm and downstream facing round-nosed (4–10) cm bridge piers—were tested under live-bed condition with flow intensity of 58 l/s for duration of 3 h. The velocity field measurements were obtained using an Acoustic Doppler Velocimeter. The results showed that the downstream facing round-nosed pier reduces local scour. The reduction in maximum scour depth was 54 % when compared to the circular pier and 40 % compared with upstream facing round-nosed pier. The downstream facing round-nosed pier reduces local scour by a volume of 83 % when compared to the circular pier. Changing the position of bridge pier (as is located downstream facing to the flow) is an effective countermeasure for reducing local scour depth. Empirical relationship was developed on the basis of obtained results. The present experimental study shows that there is no need of any alteration or modification to countermeasure scour like riprap, collar and slot. The present method also reduces costs and improves the hydraulic performance of bridge pier.

Experimental study for determination of collar dimensions around bridge pier

The shape and size of a collar is important to maximize its effect as a scour countermeasure. Current research shows that the depth of the scour hole is decreased by using rectangular collars around circular piers. This study determined the approximate optimum dimensions for rectangular collars to minimize the temporal trend of scouring around a pier model. Effects of different sizes of rectangular collars on a model pier were investigated both at the upstream and downstream of the flume. It was observed that irrespective of the rectangular collar dimensions the upstream and the downstream were estimated to be 0.86 and 1.42, respectively. The optimum collar width was estimated to be 2.8 times the diameter of the pier. By using this optimized collar dimension, the non-dimensional depth of scour reached a min value of 0.034 at 72 h. The reduction percentage of the scour depth reached 98% at 72 h.

Turbulence flow field around two eccentric circular piers in scour hole

ABSTRACTFlow pattern at single pier has been extensively studied by several investigators, but scanty work is available on turbulent flow pattern around piers placed in close proximity. The work explained in this research is concerned with an experimental study of the horseshoe vortex flow pattern and characteristics in a local equilibrium scour hole around two identical circular piers placed in the longitudinal direction to the flow with an eccentricity (transverse distance). Instantaneous three-dimensional velocities were measured by using an acoustic Doppler Velocimeter (ADV). The contours and distributions of the time-averaged velocity components, turbulence intensities and turbulence kinetic energy are presented at different azimuthal planes: 0°, 45°, −45°, 90° and −90°. Velocity vectors obtained from time-averaged velocity fields are used to show further flow features. The vorticity and circulation of the horseshoe vortex are determined by using a forward difference technique of computational hydrodynamics and the Stokes theorem, respectively. The eccentric pier arrangement and the interference between the piers play an important role in the creation and formation of the greater scour depth at the eccentric rear pier. Vortex strength of the eccentric rear pier is found higher than the front pier.

Seismic performance evaluation of circular steel bridge piers which have damage and concrete filled repair

Seismic performance evaluation of circular steel bridge piers which have damage and concrete filled repair

Estimation of scour depth around circular piers: applications of model tree

Scour around bridge piers is one of the main causes of bridge failures and is of great importance for hydraulic engineers and scientists. Prediction of the scour depth around piers is complicated, and accurate results are rarely achieved by the existing models. Recently, data mining approaches such as artificial neural networks and fuzzy inference systems have been applied successfully to predict scour depth around hydraulic structures. In this study, an alternative robust data mining approach was used for the predictions of the scour depth around piers, and the results were compared with those of three empirical approaches. Performances of developed models were tested by experimental data sets collected in laboratory experiments and field measurements, together with existing empirical approaches. Statistical measures indicate that the proposed M5′ model provides a better prediction of scour depth than the empirical approaches.