Single Bridge Pier Research Articles

Experimental study on seismic performance of a new precast segmental assembled single column bridge pier

Prefabricated bridge technology has come into wide spread use as fabricated technology has advanced, but engineering applications of fabricated bridge technology are primarily focused on the bridge superstructure, considerably restricting the use of prefabricated bridge technology for the bridge substructure due to the uncertainty in the seismic performance and damage mechanism of segmental assembled piers. Based on this, two new segment connection methods were proposed and applied to the prefabricated piers. Four specimens with a scale of 0.4 were designed and manufactured. The seismic performance of two new types of assembled single column piers, namely cone sleeve-FRC (CSF) wet joint segmental assembled pier and main reinforcement lap-UHPC (MRLU) wet joint segmental assembled pier, is investigated and compared with integral cast-in-place pier to analyze the effects of FRC and UHPC on the seismic performance of the piers, using the proposed static test. The results show that the pier connected by cone sleeve-FRC wet joint exhibits a good energy dissipation and ductility, small deformation, the highest peak bearing capacity and the best seismic performance. Based on the tests, finite element models of the members were created, and the member CSF-1, which has the best seismic performance, was parametrically analyzed by taking three influencing factors into account: axial compression ratio, longitudinal reinforcement area and hoop reinforcement spacing. It is indicated that a significant improvement in seismic performance can be achieved by reducing the hoop spacing, increasing the longitudinal reinforcement diameter and axial compression ratio.

Recorded and modeled response of the Thorndon Overbridge during multiple earthquakes

This article presents the recorded and modeled strong-motion response of a long (1.35 km) bridge located in Wellington, New Zealand during multiple sequential earthquakes. These were some of the first recordings of this kind for a New Zealand highway bridge and add to the limited database of bridge superstructure strong-motion responses recorded worldwide. The bridge experienced little damage during the earthquakes; however, analysis of the recorded responses showed the fundamental period of the bridge varied by up to 15% across these events, highlighting the system softening that can develop without any significant structural damage. Numerical models of a single bridge pier using a p-y spring foundation modeling approach were able to represent the changes in the recorded bridge pier response across the events based on multiple response metrics, suggesting that system softening was primarily due to nonlinear soil response and concrete cracking. A sensitivity analysis showed that concrete strength and the characteristics of the upper soil layers had the largest influence on the model response. Given the presence of several strong-motion stations in close vicinity to the bridge, the sensitivity to ground-motion input was also investigated. This was shown to have a more significant influence on the modeled response than the other modeling uncertainties evaluated here, with the variability in estimated deformations highlighting the difficulties involved in the back analysis of the response of structures.

Characterizing the Importance of Porosity of Large Woody Debris Accumulations at Single Bridge Piers on Localized Scour

AbstractThe accumulation of large woody debris (LWD) at bridge piers is a serious hazard to the structural integrity of bridges across watercourses worldwide. The exacerbated scour that can directly result from LWD accumulations can lead to major structural damage or even catastrophic collapse. Recent research has led to empirical equations to estimate the scour depth for given LWD accumulation size; however these are mostly based on experimental tests with prismatic and impervious solid LWD accumulations, ignoring field observations that have shown that accumulations are neither impervious nor prismatic but are porous with inverted conical shapes. In this study, we therefore investigate the effects of porous LWD accumulations having shapes commonly observed in the field on scour holes. Results reveal that LWD size and shape, and flow characteristics are the primary factors influencing the erosion of sediments at the base of bridge piers. However, the porosity of accumulations is also observed to have a considerable effect on the size and maximum depth of scour holes. In particular, porous LWD reduce the maximum scour depth by up to 50% (and on average in the range of 5%–25%) relative to the respective solid impervious accumulation. The results shown in this study also provide a practical tool for arriving at more realistic and less conservative estimates of scour depths at bridge piers when affected by LWD accumulations.

Non-linear finite element modeling of damages in bridge piers subjected to lateral monotonic loading

Bridges are among the most vulnerable structures to earthquake damage. Most bridges are seismically inadequate due to outdated bridge design codes and poor construction methods in developing countries. Although expensive, experimental studies are useful in evaluating bridge piers. As an alternative, numerical tools are used to evaluate bridge piers, and many numerical techniques can be applied in this context. This study employs Abaqus/Explicit, a finite element program, to model bridge piers nonlinearly and validate the proposed computational method using experimental data. In the finite element program, a single bridge pier having a circular geometry that is being subjected to a monotonic lateral load is simulated. In order to depict damages, Concrete Damage Plasticity (CDP), a damage model based on plasticity, is adopted. Concrete crushing and tensile cracking are the primary failure mechanisms as per CDP. The CDP parameters are determined by employing modified Kent and Park model for concrete compressive behavior and an exponential relation for tension stiffening. The performance of the bridge pier is investigated using an existing evaluation criterion. The influence of the stress–strain relation, the compressive strength of concrete, and geometric configuration are taken into consideration during the parametric analysis. It has been observed that the stress–strain relation, concrete strength, and configuration all have a significant impact on the column response.

Evaluation of angled splitters as scour countermeasure at circular piers

Scour around bridge piers is local phenomenon may cause complete failure for the hydraulic structure. This study explored experimentally using splitter plates at specific angles installed upstream single circular bridge pier to improve the nearby flow field and minimize the local scour. Ninety runs were carried out considering 9 splitter models. Four splitter lengths and 3 vertex angles were used. The splitter lengths were between 0 and 1.5 times of pier diameter, each was tested for 3 vertex angles ranged between 0° and 30°. The tests were done under 9 different hydraulic conditions including 3 discharges of 75, 100, and 125 l/s and 3 tailwater depths of 12.5, 15, and 17.5 cm. The turbulent flow conditions were investigated by plotting velocity profiles at different sections. The bed configurations under clear water conditions were presented. The results of pier without splitter were used as reference. The study outcome that the local scour depth was decreased by the increase of splitter length and vertex angle. The near-bed flow velocity and the corresponding Froude No. downstream of the pier was minimized for 1.5D splitter length at 30° vertex angle and the minimum scour geometry was located. The effectiveness of splitters were remarkable by the decrease of flow discharge and increase of tailwater depth provided that the discontinuity of scour hole length in case of multi-circular piers. Regression analysis was employed to develop empirical formula for the estimation of maximum scour depth around circular pier with splitter.

Influence of Dynamic Woody Debris Jam on Single Bridge Pier Scour and Induced Hydraulic Head

A woody debris jam around a bridge pier causes a change in flow structure and results in additional scour and an increase in the hydraulic head upstream of the pier, threatening its stability and safety. In the present paper, the spatio-temporal formation of a dynamic woody debris jam formed piece by piece of debris wood was used to investigate the influence of woody debris jams from a life-cycle perspective which included the processes of its formation, growth, failure, and rebirth. Several debris jams were formed in sequence during each experimental test. The results showed that the additional scour generated by the first woody debris jam compared with the scour depth without debris was a function of blockage ratio of the first debris jam, while the influence of the subsequent woody debris jams depended on their dimensions compared with the previous jam. When the subsequent debris jam’s dimensions were larger than the previous one, the scour further increased; otherwise, the scour remained constant and equal to the previous one. In addition, the debris-induced hydraulic head was analyzed and found to be correlated with the Froude number and the debris jam dimensions.

Experimental Study of Inclined Bridge Pier Scouring

The bridges are one of important structures in any country. The failure of bridges occurs due to many factors including design flaws and manufacturing construction errors. Among all imperfections scouring around the pier is the most detrimental. So, the estimation of local scouring around a bridge pier is of fundamental importance for the safe design of bridges. Although numerous researches have been done on local scouring around a single bridge pier. The present study investigates the effect of angle of inclination of dual bridge pier configuration on local scouring around bridge piers. Principally rectangular shaped dual bridge piers were installed in sand bed of laboratory flume at angle of inclination of 0°,7°,12°,15° and 19° with vertical respectively. Three different flow rates 9, 14 and 18L/sec were considered during each trial. The duration of each trial was kept around 2 hours. The scour depth was measured separately around both piers with the help of point gauge under clear water condition. The value of scour depth around upstream pier was larger as compared to downstream pier because of the lower strength of horseshoe vortices around downstream pier. From the experimental results, it can be concluded that there is an inverse relationship between the angle of inclination and scour depth, an increase in the angle of inclination leads to decrease in scour depth around both piers. The value of scour depth was maximum when piers were at 0° and minimum at 19°. It was also found that scour depth increases with the increase in flow rate.

Adaptation of Selected Formulas for Local Scour Maximum Depth at Bridge Piers Region in Laboratory Conditions

The study aimed to adapt selected formulas for the estimation of the maximum depth of local scour in the area of the bridge pillar model: Begam formula, Laursen and Toch equation and the equation included in the Regulation of the Polish Minister of Transport and Marine Economy of 30 May 2000 on technical requirements for road engineering structures and location of these structures. The results of own laboratory tests were used for the adaptation. A total of 19 series of measurements with different durations, water flow rates and water depths were performed. The tests were carried out on a model of a washable flume model with a sandy bed, with a single cylindrical bridge pier. The formulas were optimized using the Monte Carlo sampling method. The best match among the original formulas was obtained for Laursen and Toch’s formula (mean relative error 15.3%). For Begam’s formula, an average relative error of 21.6% was received, and for calculations using the Regulation equation, a relative error of 30.1% was obtained. Optimization of formulas using the Monte Carlo sampling method resulted in a formula that describes laboratory data with a mean relative error of 8.8% based on the Begam equation, a mean relative error of 13.8% based on the Laursen–Toch equation, and 28.5% for the formula based on equation included in the Regulation.

Optimal Octagonal Hooked Collar Countermeasure to Reduce Scour Around a Single Bridge Pier

Pier modification countermeasures are essential as they play a vital role in protecting pier against local scour action. Current study investigates experimentally the scour around vertical pier of octagonal cross section with pier modification such as newly proposed octagonal hooked collar is explored, in steady uniform state, under clear water condition. The results of pier scour without any modification were used as a reference to compute the efficiency of hooked collar provision around octagonal pier. The results show that by increasing the hooked collar width up to 2.5 Wp reduced maximum scour depth significantly. However, the experimental investigation revealed that the best combination to be with a hooked collar width of 2.5 Wp, having sidewall height 0.45 Wp. The best combination minimized around 73.3 % of scour hole depth, compared to octagonal pier without any modification. Using experimental results, a new equation is proposed to predict the scour depth around a bridge pier fitted with hooked collar. Moreover, a relation was developed for maximum scour depth and scour hole volume. Results indicate that the scour hole volume around a bridge pier increases quadratically with maximum scour depth.

Effect of Interaction between Bridge Piers on Local Scouring in Cohesive Soils

Local scour at the piers is one of the main reasons of bridge foundation undermining. Earlier research studies focused mainly on the scour at a single bridge pier; nevertheless, modern designs of the bridges comprise wide-span and thus group of piers rather than a single pier are usually used to support the superstructure. The flow and scour pattern around group of piers is different from the case of a single pier due to the interaction effect. Reviewing the literature of local scour around bridge piers group revealed that the local scour around bridge piers group founded in cohesive soil bed was not investigated, and most of the scour studies were related to scour in cohesionless soils. The objective of the present study is to investigate the effect of the interaction between two in-line (tandem) circular bridge piers of variable spacings founded in cohesive soil on the local scour. A set of laboratory flume experiments were conducted under the clear-water scour condition to investigate this effect. This study is the first that investigates experimentally the scour around group of bridge piers in cohesive bed. It was found that the maximum scour depth at the upstream pier of the two in-line piers occurred at a spacing of two times the diameter of the pier, scour at the downstream pier was reduced due to a sheltering effect, the interference effect will be reduced for pier spacings larger than three times of the pier diameter. A recent pier scour equation was used to estimate the scour depths at the two in-line piers in cohesive soil and compare the estimated value with the measured scour depths in the laboratory. The comparison indicated that the proposed scour equation overestimates the scour depths at both the upstream and the downstream pier.

Reduction of local scour around a bridge pier by using different shapes of pier slots and collars

Abstract Local scour around bridge piers is one of the main causes of bridge failure all over the world. Experimental and hydraulic models were carried out to investigate two types of scour reduction methods around a single cylindrical pier, namely the pier's slots and collars. The efficiency of various types of pier slots and circular collars around the pier's base in reducing scour were studied. A new shape of a conical collar was developed by the authors and examined along with other shapes. The results revealed that collars, in general, have more influence in reducing scour depth than slots made in the front and rear of bridge piers. The sigma-slot acts better than other tested slots, with a reduction in the scour depths of 59.3% and 52.8% at the upstream and downstream of the pier, respectively. On the other hand, the conical collar appeared to be the most effective collar shape in reducing the scour around the bridge pier, with a 61.1% reduction in the scour depth downstream of the pier. A three-dimensional laser scanner was used to capture the bed topography at the end of each experiment and contour maps of the deformed bed were produced. A one-dimensional Hydrologic Engineering Center-River Analysis System model was developed with a single bridge pier to predict the scour depth around the pier in an attempt to introduce new values for the pier nose shape factor, , which describes the tested piers.

Scour Depth at Single Cylindrical Bridge Piers with Debris Jam: An Experimental Comparative Study.

Rivers may carry a considerable amount of debris during floods, and the accumulation of this debris around bridge piers can change the hydraulic behaviour of flow fields and influence scour depth development. In this study, the effect of debris jam on scour depth at cylindrical bridge piers was investigated and a comparison carried out for the main existing empirical formulas. A series of 27 tests of rectangular geometry in three different groups according to width, length, submerged depth, and blocked area were studied. The results showed that the accumulation of debris increased scour depth from 10.3% to 62.1%, 22.4% to 103.4%, and 20.7% to 139.7% as the percentage blocked area of debris increased from 2.07% to 6.2%, 5.52% to 16.55%, and 8.96% to 26.89% for groups (1), (2), and (3) respectively. The comparison of the experimental results with the most commonly used empirical formulas revealed general overestimation of scour depth with debris accumulation. The Richardson and Davis (1995) and Lagasse et al. (2009) formulas were the most acceptable methods for scour prediction under debris jams, though further study is recommended for bridge pier scour depth estimation in the presence of debris.

Numerical simulation of the turbulent flow around a complex bridge pier on the scoured bed

The present study aims to contribute to the numerical simulation of the flow behavior around a complex bridge pier with the scoured bed. For this purpose, a custom Large Eddy Simulation model was developed in which the pier and bed geometries are modeled in a structured grid system with orthogonal grid lines. The top free surface was treated as a shear-free rigid-lid. Moreover, a wall function was employed at the wall boundaries to consider the wall roughness effect on the predictions. This way, reliable numerical simulations could be performed at high Reynolds numbers with low computational cost. The developed numerical model was firstly validated by considering two cases (flow over periodic hills and flow around a single bridge pier on a scoured bed) and then the model was applied to a complex bridge pier for a scoured bed. The obtained numerical results were found to be in good agreement with the corresponding experimental and numerical results. Moreover, this study enabled to characterize the most relevant flow features of the studied cases. Overall, the highest values of the flow parameters and the small flow structures were numerically predicted in the regions where no experimental results are available due to measuring instruments limitations. According to the obtained results, the present numerical model can be considered as an adequate tool to investigate the turbulent flow features near complex geometries in a simple, fast and accurate way.

Bed topography variations in bend by simultaneous installation of submerged vanes and single bridge pier

Every year, thousands of bridges around the world are destroyed by scouring around their piers. One of the methods to control and protect the piers against scouring is to use submerged vanes. The purpose of this paper is to investigate the effect of upstream submerged vanes on scouring around the bridge pier and bed topography changes. For doing experiments, a cylindrical bridge pier and several numbers of submerged vanes with various angles and lengths were used in a laboratory flume with a 180° sharp bend. The results illustrate that by using three submerged vanes, sediments have progressed less toward the downstream. Moreover, the surrounded rectangle on scour hole around the bridge pier has the largest and smallest dimensions in test with four submerged vanes, length of 1.5 times the pier diameter and angle of 35° relative to the tangent at the bend mid-section, and in a test with two submerged vanes, length of equal to the pier diameter, and angle of 15°, respectively.

Experimental and Numerical Comparison of Flow and scour Patterns around a Single and Triple Bridge Piers Located at a sharp 180 degrees Bend

Placement of bridge piers along rivers creates a complex 3D flow pattern which disrupts normal river flow and the resulted turbulence erodes alluvial sediments around the pier. In this research, SSIIM model has been used to simulate flow and scour patterns when no pier, one pier, and triple piers are placed at a 180 degrees bend and the results are compared with those of experiments. The piers are vertical. The simulated channel was 1 m wide with a U-turn having the relative curvature radius of 2 carrying a volumetric flow of 70 l/s the flow depth at the beginning of the bend is 18 cm. Results showed that SSIIM is well capable of simulating bed form changes and flow patterns such that at the bend with triple piers error in maximum scour and sedimentation was only 4%, in maximum transverse velocity 12%, in maximum longitudinal velocity 13%, and in maximum vertical velocity 19%. In general, SSIIM model satisfactorily simulates the location and value of local scour arising from single and series piers in numerical simulation of the flow and scour. In flow pattern simulation, the errors and differences are greater under moving bed conditions than a rigid bed.

Local scour around two side-by-side cylindrical bridge piers under ice-covered conditions

In the current study, 108 flume experiments with non-uniform, cohesionless sediments have been done to investigate the local scour process around four pairs of side-by-side bridge piers under both open channel and ice-covered flow conditions. Similar to local scour around bridge piers under open channel conditions and a single bridge pier, it was observed in the experiments that the maximum scour depth always occurred at the upstream face of the pier under ice-covered conditions. Further, the smaller the pier size and the greater the spacing distance between the bridge piers, the weaker the horseshoe vortices around the bridge piers, and, thus, the shallower the scour holes around them. Finally, empirical equations were developed to estimate the maximum scour depth around two side-by-side bridge piers under both open channel and ice-covered flow conditions.

Seismic collapse assessment of bridge piers constructed with steel fibers reinforced concrete.

Steel fiber is one of the most widely used reinforcements to improve the performance of concrete members. However, few studies have been proposed to study the seismic performance of bridge piers constructed with steel fiber reinforced concrete. This paper presents the collapse vulnerability assessment of typical single bridge piers constructed with steel fibers. Fiber element models of RC bridge piers with and without steel fibers are firstly built by selecting suitable cyclic constitutive laws of steel fiber reinforced concrete, and then calibrated using the experimental results. The seismic capacity and inelastic demand of RC piers with steel fibers are quantified using both nonlinear static pushover analyses and nonlinear incremental dynamic analyses (IDA). In order to conduct the IDA, a suite of 20 earthquake ground motions are selected and scaled to different levels of peak ground acceleration (PGA). Collapse fragility curves are then generated using the maximum drift ratio of piers as the engineering demand parameter (EDP). In order to investigate the impact of various parameters on the collapse fragility curves, six parameters are considered in the parametric study: peak compressive strength of concrete, yield strength of steel, longitudinal reinforcement ratio, axial load ratio, transverse hoops ratio and steel fiber content. It was observed that the concrete strength, longitudinal reinforcement ratio and steel fiber content could significantly affect the collapse fragility curve of the bridge piers with steel fibers.

Effect of Bridge Pier Shape on Scour Depth at Uniform Single Bridge Pier

Bridge pier scouring may lead to the bridge failure and the shape of bridge pier itself is one of the main factor to control scouring around bridge pier. The amount of sediment which is removed from the boundary of bridge pier is called bridge pier scouring and the depth up to which sediment removed is called scour depth. Scouring results, the exposure of foundation, eventually leading to bridge failures. Assessment of the maximum scour that can be faced by pier has a vital role in the design of bridge foundation. Different techniques are used to minimize the scouring effect in order to control the bridge failure. In this study effect of bridge pier shape on scouring was checked on four different shape i.e. circular, oval, square and octagonal. Each pier shape was tested against three different values of flows i.e. 16, 22.50 and 29.50 liter/sec. Uniform bed material of standard deviation (g = 1.21) and median size (D50 = 0.28 mm) was used for all tests. Scour is measured with the help of point of gauge and bed is levelled before every experiment. Experimental results show that minimum scour is observed for octagonal bridge pier and maximum for square bridge pier while circular and oval faced intermediate scour depth relative to square and octagonal bridge pier. It is concluded that scour has reduced to 22% when octagonal pier was used compared to circular one.

Impacts of bridge piers on water level during ice jammed period in bend channel–An experimental study

Experiments are carried out in an “S-shaped” flume in the laboratory under both open flow and ice-jammed conditions to study the impacts of bridge piers in a bend channel on the variation of the water level. The variations of the water level under the ice jammed condition with bridge piers are compared to those without bridge piers in an 180° bend channel. Results indicate that the bridge piers in the S-shaped channel have obvious impacts on the ice accumulation and the water level. The increment of the water level with the presence of the bridge piers is less than that without the bridge piers in the channel. Different arrangements of the bridge piers result in different increments of the water level. When one bridge pier is installed in the straight section of the channel (between 2 bends) and another one at the bend apex (for a convex bank), the increment of the water level during the equilibrium ice jammed period is between that with a single bridge pier located in the straight section of the bend channel and that with a single bridge pier located at the bend apex. It is also shown that the increment of the water level during the equilibrium ice jammed period increases with the increase of the average thickness of the ice jams.

Nonlinear response of bridge piers on inclined pile groups: the role of rocking foundation input motion

This paper presents first results of an on-going research focused on the effects of piles layout and inclination on the nonlinear seismic response of bridge piers. The analysis methodology, based on the substructure approach, is firstly presented. The soil-foundation system is studied in the frequency domain according to a numerical model developed by the authors while the inertial interaction analysis of the superstructures is carried out in the time domain to capture the nonlinear structural behaviour. A suitable lumped parameter model is used to approximate the frequency dependent behaviour of the soil-foundation impedances in the time domain analyses. The procedure is applied to some case studies constituted by single bridge piers founded on medium stiff and soft clayed soil deposits. Pile groups with piles of different inclinations are considered, as well as piers with different fundamental periods and yielding bending moments of the base cross sections, to simulate systems with different ductility capacity. Analyses results show the key role of the foundation rocking on the superstructure response and demonstrate that inclined pile foundations may have a significant impact on the superstructure response, reducing the pier head displacements and ductility demand.