Circular Bridge Piers Research Articles

Fiber-based damage analysis of reinforced concrete bridge piers

A fiber beam-column element is adopted to simulate the damage development process of reinforced concrete (RC) bridge piers under quasi-static and earthquake loadings considering global buckling and low-cycle fatigue of longitudinal bars. The tensile strain and low-cycle fatigue are used to represent the damage to longitudinal bars while the compression strain is adopted to calculate the damage to the cover concrete. A section damage index is proposed based on the material damage definition and bridge performance assessment. A set of circular RC bridge piers tested under different uniaxial quasi-static loading regimes are adopted to verify the reliability of the fiber beam-column element and the proposed damage model. Square RC columns subjected to different uniaxial and biaxial quasi-static loadings are used to verify the applicable scope of the fiber element and the damage index in biaxial quasi-static loading. In addition, a series of shaking table model tests on square, rectangular and circular piers subjected to bilateral earthquake ground motions are simulated to further verify the versatility of this model. The results show that, the fiber beam-column element can simulate RC columns/piers with different sections and loading regimes with good accuracy. The damage index proposed in this paper is compared against experimental results and other damage indices and it is found that the proposed index can reflect the damage state at any stage and the gradual accumulation of damage in RC columns/piers more convincingly than most other indices available in literature.

Experimental response of an existing RC bridge with smooth bars and preliminary numerical simulations

The paper discusses the experimental seismic performance assessment of a structural prototype simulating typical existing highway bridges which were designed with poor seismic details. The structural system is a reinforced concrete (RC) 1:3 scale single span bridge which has been tested dynamically with shaking tables by considering strong motions of the 1980 Irpinia (Italy) earthquake. Low-strength concrete and smooth bars were used for the RC circular bridge piers of the tested prototype. Comprehensive modal response analysis has been carried out for the single piers and for the bridge sub-assemblage to estimate period elongations and variations of equivalent viscous damping coefficients at increasing levels of strong motions. The effects of cumulative damage induced by earthquake sequences have also been investigated experimentally. The sample bridge pier possesses low aspect ratio; nevertheless the piers exhibited a flexural response. Fixed-end rotations, with significant longitudinal reinforcement slip, were observed at the base of the bridge pier at about 0.40% lateral drift ratio. As a consequence, a rocking mechanism of the bridge pier initiated; such mechanism affected significantly the pier response at large shaking intensities. An in-depth analysis of local and global response quantities has been provided in order to accurately identify the structural behaviour. Finally, available analytical formulations and refined numerical models were considered to simulate the earthquake response of the tested bridge. The pier lateral response has been investigated by means of push-over analysis and nonlinear time histories. The accuracy of the proposed models, the differences and recommendations for numerical modelling of bridge piers with smooth internal reinforcements are also discussed.

Effect of downward seepage on turbulent flow characteristics and bed morphology around bridge piers

In this work, experimental investigations have been pursued to analyse the influence of downward seepage on the turbulent characteristics of flow and corresponding changes in vortex structure around circular bridge pier in alluvial channel. Experiments were conducted in sand bed channel with circular piers of different sizes for no seepage, 10% seepage and 20% seepage cases. The measurement of turbulent flow statistics such as velocity and Reynolds stresses is found to be negative within the scour hole at upstream of the pier whereas application of downward seepage retards the reversal of the flow causing a decrement in the velocity and Reynolds stresses. Higher Reynolds shear stress prevails at the downstream side because of the production of wake vortices. Contribution of all bursting events to the total Reynolds shear stress production has been observed to increase with downward seepage. The analysis of integral scale suggest that size of eddies increases with seepage, which is responsible for increase in particle mobility. Initially rate of scouring is more which abatements gradually with expanding time as well as with the increased of downward seepage. Presence of downward seepage reduces the depth and length of vortex and shifts towards downstream side of the pier.

Characterization of radial and circumferential mechanical energy components in bi-directional nonlinear seismic response of steel bridge piers

In this study, the bi-directional nonlinear elaso-plastic seismic response of steel bridge piers subjected to bi-directional ground motions is analyzed with a particular interest in the role of the radial and circumferential components of mechanical energy. In order to explore the influencing factors to the maximum bi-directional seismic response, dynamic characteristics of a circular steel bridge pier are expressed by two modeling techniques: the multiple shear spring (MSS) model, and the fiber model. The calculated bi-directional dynamic responses of the steel bridge pier models under artificially generated bi-directional ground motions are characterized by introducing a technique to divide the strain and kinetic energies to the radial and circumferential components. The analysis result indicates that the level of circumferential strain energy that effectively contributes to dissipation of the total kinetic energy is of great importance in assessing the maximum bi-directional response. When the two models are subjected to the identical bi-directional ground motion, the circumferential strain energy induced in the fiber model is higher than that obtained by the multiple shear spring model, resulting in smaller radial displacement. Also, the analyses of the fiber model for various cases of directivity property of the input bi-directional seismic ground motion show that the bi-directional response is smaller than the unidirectional response in some cases. The reason can be explained by higher circumferential strain energy which can be related to the reduction of radial displacement in those cases.

Study of the time-dependent clear water scour around circular bridge piers

Abstract The local scour around bridge piers influences their stabilities and plays a key role in the bridge failures. The estimation of the maximum possible scour depth around bridge piers is an important step in the design of the bridge pier foundations. In this study, the temporal evolution of local scour depths as well as the equilibrium scour depths were analyzed. The experiments were carried out in a rectangular flume by using uniform sediment with median diameter of 3.5 mm and geometric standard deviation of 1.4. The diameters of the tested circular bridge piers were 40 mm, 80 mm, 150 mm and 200 mm. The flow and scour depths were determined by ultrasonic sensors. The experiments were realized in clear water conditions with various constant flow rates. The experimental findings were compared with those calculated from some empirical equations existing in the literature. A new empirical relation involving the flow intensity, the relative water depth and the dimensionless time is also introduced. The advantage of this proposed relation is that the only parameter requiring the calculation is the critical velocity, other parameters being known geometric and hydraulic parameters. The performance of this relation was tested by using experimental data available in the literature, and a satisfactory compatibility was revealed between the experimental and numerical results.

Seismic collapse assessment of non-seismically designed circular RC bridge piers retrofitted with FRP composites

The seismic vulnerability of a bridge pier is generally expressed in terms of fragility curves, which reveal the conditional probability of exceeding a predefined performance damage state at different levels of earthquake intensities. This research presents the results of fragility curves of typical single circular reinforced concrete (RC) bridge piers. The different parameters considered in the analysis include: the strength of concrete, yield strength and amount of longitudinal steel rebar, level of axial load, shear span-depth ratio, and carbon fiber reinforced polymer confinement layer. Nonlinear static pushover analysis (NSPA) is conducted along with incremental dynamic analysis using suits of earthquake ground motions with scaled peak ground acceleration (PGA) to investigate the nonlinear dynamic behavior of the retrofitted piers. The impact of various parameters is evaluated under probability point of view in terms of its influence on the bridge pier fragility curve. Considering collapse drift as demand parameters, fragility curves were generated with different parameters of non-seismically designed RC circular bridge piers. It was observed that the amount of reinforcement, shear span-depth ratio, and level of the axial load could significantly affect the collapse fragility curve of the retrofitted bridge piers.

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.

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.

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 Evaluation of Repaired and Retrofitted Circular Bridge Piers of Low-Strength Concrete

An experimental investigation was carried out to study the effect of retrofitting on change in dynamic properties of 1/4 scaled damaged and undamaged bridge piers of low-strength concrete. Response of three bridge piers, subjected to cyclic lateral loads and free vibration tests under constant axial loading, was evaluated. One of the piers was tested twice: firstly, it was tested up to damaged state, and then it was repaired with single layer of carbon fiber-reinforced polymer (CFRP). This repaired column was then subjected to the same type of loading as the original one. Third pier was retrofitted in undamaged state with single layer of CFRP. It was observed that ductility of retrofitted column at 2% drift level was 39% higher than that of original column. However, ductility of repaired column was improved to original level. Cumulative energy dissipation capacity of retrofitted column was also improved up to 39.38%, whereas energy dissipation capacity of damaged retrofitted was recovered to original state. After subsequent cycles, improvement in energy dissipation capacity was 25.8 and 18% in retrofitted and repaired columns, respectively.

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.

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.

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

Simplified formula of hydrodynamic pressure on circular bridge piers in the time domain

The hydrodynamic pressure expression based on radiation theory is very complicated and temporal convolution in the time domain that lead to their values difficult to be calculated. The Morison equation is a semi-empirical formula and its inertia coefficient and drag coefficient are difficult to be determined accurately. Therefore, the simplified formula based on radiation theory which is concise, accurate and global decoupling in the time domain is presented by introducing three dimensionless parameters including frequency ratio, wide depth ratio and relative height of bridge pier. By analyzing the analytical formula of hydrodynamic pressure detailed, the hydrodynamic pressure formula in the frequency domain is simplified by segmenting. The simplified formula which is global decoupling in the time domain can be expressed in the form of added mass in low frequency vibration and can be expressed in the form of added mass and added damping in high frequency vibration. The calculation results show that the simplified method is in good agreement with the analytical formula. Compared with the Morison equation whose coefficients need to be selected by experience, the coefficients of the simplified formula are only related to the relative size of bridge piers.

Three-dimensional analysis of coherent turbulent flow structure around a single circular bridge pier

The coherent turbulent flow around a single circular bridge pier and its effects on the bed scouring pattern is investigated in this study. The coherent turbulent flow and associated shear stresses play a major role in sediment entrainment from the bed particularly around a bridge pier where complex vortex structures exist. The conventional two-dimensional quadrant analysis of the bursting process is unable to define sediment entrainment, particularly where fully three-dimensional flow structures exist. In this paper, three-dimensional octant analysis was used to improve understanding of the role of bursting events in the process of particle entrainment. In this study, the three-dimensional velocity of flow was measured at 102 points near the bed of an open channel using an Acoustic Doppler Velocity meter (Micro-ADV). The pattern of bed scouring was measured during the experiment. The velocity data were analysed using the Markov process to investigate the sequential occurrence of bursting events and to determine the transition probability of the bursting events. The results showed that external sweep and internal ejection events were an effective mechanism for sediment entrainment around a single circular bridge pier. The results are useful in understanding scour patterns around bridge piers.

Study on the Ultimate Limit State of the Curvature for Circular Section Reinforced Concrete Bridge Pier

The ultimate limit state of the curvature for circular section reinforced concrete bridge pier was studied from the uncertainty of the deformation capacity. This article firstly uses the bridge pier with the diameter of 1.0m as the benchmark pier to study the relations between the ultimate limit state of the dimensionless yield, service and damage control curvature and the axial compression ratio, longitudinal reinforcement ratio and stirrup ratio. Results have shown that axial compression ratio is the main factor influencing the average value at the ultimate limit state of dimensionless yield and service horizontal curvature, while the axial compression ratio and stirrup ratio are main factors influencing the average value at the ultimate limit state of dimensionless damage control horizontal curvature. Then this article built the approximate formula for the calculation of diameter adjustment coefficient for the piers with other sections and diameters corresponding to the ductility at different ultimate limit states by means of regression analysis.