Existing Bridge Piers Research Articles

Rapid design method for composite emergency steel piers with thin-walled steel tube framework and discussion on "temporary-permanent" transition

To address the conflict between the reserve of repair materials for existing bridge piers and the demands for emergency repairs, as well as the challenge of converting temporary emergency structures into permanent ones without significant disassembly, a novel composite emergency steel pier has been developed. This pier utilizes commonly available thin-walled steel tube sections as the framework, I-beams as the connecting elements, and incorporates a "temporary-permanent" transition function. Taking the emergency steel pier for medium-height bridge piers in high-speed rail systems as an example, this study introduces three evaluation metrics—security coefficient (n), stability coefficient k), and variation coefficient (V)—analyzing the factors influencing the design and application thresholds of the emergency steel piers from perspectives of strength, stability, and load distribution uniformity. Based on this, a rapid design method for composite emergency steel piers with thin-walled steel tube frameworks that does not require numerical simulation has been developed and experimentally validated. Research findings indicate that when used for the emergency repair of medium-height or lower bridge piers in high-speed railways, the column line stiffness of the thin-walled steel tube framework composite emergency steel piers should range between 0.34 × 10 exp7 kN/mm to 4.15 × 10 exp7 kN/mm. The transverse and longitudinal spacing of the columns should be 1 m to 3 m and 1.5 m to 3 m respectively. The line stiffness of the plinth beams I and II should be greater than 0.69 kN/mm and 1.01 kN/mm respectively. Within these parameter ranges, the emergency steel pier will not experience strength failure or instability, and the load distribution among the columns remains uniformly favorable. In applications to other scenarios, the rapid generation of composite emergency steel piers with thin-walled steel tube frameworks can be achieved by following three steps: parameter selection and structural configuration determination, calculation of the pier-beam linear stiffness ratio, and criterion-based result verification. The rapid design and implementation of composite emergency steel piers help alleviate the contradiction between material stockpiling and repair demands. Furthermore, the pre-designed "temporary-permanent" transition functionality facilitates integrated operations for emergency repairs and permanent restorations.

Three-Dimensional Turbulent Simulation of Bivariate Normal Distribution Protection Device

In response to the deficiencies in existing bridge pier scour protection technologies, this paper introduces a novel protective device, namely a normal distribution-shaped surface (BND) protection devices formed by rotating a concave normal curve. A three-dimensional turbulent SST k−ω model is constructed, and physical model experiments of conical surfaces are conducted to validate the mathematical model. The simulation analyzes longitudinal water flow, downflow, vorticity intensity, and shear stress within normal and conical surfaces. The results show that the downflow distribution in front of the pier spans a relative water depth of (−0.45, 0.67), with a peak velocity approximately 70% of the longitudinal flow velocity. Circulation forms within the surfaces, with the main vortex flux inside the BND being 33% lower than that inside the conical surface. The maximum shear stress coefficient inside the BND can reach 9, and the protective surface isolates the bed from the flow to prevent scouring by high shear stress. The velocity gradient at the edge of the surface is small, and the edge shear stress of the 3D normal distribution-shaped surface (BND) protection device is only one-third of that of the conical surface, preventing edge scouring. The large shear stress and its distribution area decrease monotonically with the increase in surface width. When the surface width is four times the diameter, the distribution range of the shear stress coefficient greater than 1 is very small. The study of three-Dimensional turbulence within the BND provides a numerical basis for an anti-scour design.

Modeling of scour depth in the existing bridge piers with and without an adjacent parallel bridge

Modeling of scour depth in the existing bridge piers with and without an adjacent parallel bridge

Seismic Fragility Analysis of an Existing Bridge Pier

The main objective of this paper is to develop the fragility curves for an existing bridge having circular pier by static nonlinear analysis (Pushover Analysis). In this study, a cantilever circular bridge pier which is located in Assam, a highly seismic zone in India is considered for development of seismic fragility curve. Capacity of the bridge has been determined by Pushover analysis of bridge pier and demand parameter of the bridge were obtained by using ATC 40 Capacity Spectrum method and IS 1893:2016 (Part 1) along with IRC 6:2017. Civil Software SAP 2000 version 20 is used to analyze the bridge pier. The fragility curves of the pier have been constructed assuming a lognormal distribution. The evaluation results presented here describes the probabilistic seismic failure of the bridge pier and its capacity to meet the desired performance level.

Seismic performance of prefabricated square hollow section piers strengthened by jacketing using UHPC and high-strength steel

Pier damages have become a primary contributing factor to bridge seismic damage, because they may cause serious loss of integrity and even the collapse of the whole bridge structure. Therefore, developing and improving methods for the seismic strengthening of existing bridge piers can play a significant role in preventing bridge failures. In this study, ultra-high-performance concrete (UHPC) and HTRB600E high-strength steel bars were used to strengthen prefabricated square hollow section piers that had undergone severe flexural damage due to seismic demands. By conducting quasi-static tests on the prefabricated piers before and after strengthening, seismic performance indices, such as the hysteresis curve, skeleton curve, energy dissipation, stiffness degradation, residual displacement, and curvature, were compared and analysed. Under cyclic loading, the deformation of the strengthened pier shaft section was small, and no evident plastic failure was observed. The unreinforced pier shaft exhibited a clear bending shear failure mode, with a plastic hinge first developing at the top of the strengthened shaft section. Based on the quasi-static test results, a refined finite element model of the pier was implemented and verified. By varying the thickness and height of the UHPC reinforcing layer and the strength of the steel bars, their influence on the seismic capacity of the pier was explored. The experimental results indicate that the jacketing using UHPC and high-strength steel bars significantly improved the flexural capacity, energy dissipation, and initial stiffness of the retrofitted specimens and effectively restored and enhanced their seismic performance.

Cyclic Behavior of Retrofitted Low- and High-Strength Concrete Scaled Bridge Piers under Quasistatic Loading

Bridges are vulnerable to devastation in the earthquake, resulting in the closure of the whole transport system of the particular region. Generally, pre-Kashmir earthquake bridges in Pakistan were not designed according to present seismic zoning requirements. Therefore, it is critical to evaluate their seismic performance and accordingly enhance their strength, stiffness, and thus reliability. Seismic retrofitting of existing bridges with CFRPs (carbon fiber-reinforced polymers) may be planned for typical bridge types of Pakistan. High-strength concrete (HSC) is now widely used in bridge construction, and the seismic behavior of typical bridge piers being a key component needs to be assessed. This investigation aims to evaluate the seismic performance of HSC piers before and after retrofitting in association with the earlier research in Pakistan on low-strength concrete prototypes. An experimental program was executed wherein scaled-down (4 : 1) HSC (6192 psi) RC bridge pier prototypes with axial load at the top were subjected to quasistatic cyclic loadings (QSCLs) under controlled drifts. The damaged pier prototypes were retrofitted with CFRP sheets beside another set of undamaged retrofitted models. The samples were tested under QSCL against several drift levels ranging from 0 to 5%. Hysteresis loops were drawn for each sample. The tests were studied for the assessment of the structural behavior of the prototypes. The results for the control models, damaged retrofitted models, and undamaged retrofitted models of low-strength concrete (LSC, 1800 psi and 2400 psi) obtained from doctoral research by Ali and Iqbal were compared with corresponding models of high-strength concrete (6192 psi). The outcomes clearly show a noteworthy increase in lateral load carrying capacity, ductility, strength, and energy absorption on an increase in concrete strength and retrofitting of the prototypes. The numerical modeling of these piers was in consistence with the experimental results. When retrofitted with CFRP, the existing bridge piers will enable the bridge stock to withstand high-intensity future earthquakes and lessen their seismic vulnerability against prospective damages.

Experimental Study on the Behavior of Existing Reinforced Concrete Multi-Column Piers under Earthquake Loading

When a seismic force acts on bridges, the pier can be damaged by the horizontal inertia force of the superstructure. To prevent this failure, criteria for seismic reinforcement details have been developed in many design codes. However, in moderate seismicity regions, many existing bridges were constructed without considering seismic detail because the detailed seismic design code was only applied recently. These existing structures should be retrofitted by evaluating their seismic performance. Even if the seismic design criteria are not applied, it cannot be concluded that the structure does not have adequate seismic performance. In particular, the performance of a lap-spliced reinforcement bar at a construction joint applied by past practices cannot be easily evaluated analytically. Therefore, experimental tests on the bridge piers considering a non-seismic detail of existing structures need to be performed to evaluate the seismic performance. For this reason, six small scale specimens according to existing bridge piers were constructed and seismic performances were evaluated experimentally. The three types of reinforcement detail were adjusted, including a lap-splice for construction joints. Quasi-static loading tests were performed for three types of scale model with two-column piers in both the longitudinal and transverse directions. From the test results, the effect on the failure mechanism of the lap-splice and transverse reinforcement ratio were investigated. The difference in failure characteristics according to the loading direction was investigated by the location of plastic hinges. Finally, the seismic capacity related to the displacement ductility factor and the absorbed energy by hysteresis behavior for each test were obtained and discussed.

Seismic Fragility Analysis of Bridge Pier

Bridges are classified as lifeline structures as they need to be functional in an earthquake event. The performance-based analysis of the existing bridges is important for the stakeholders. Information on seismic performance in terms of fragility of existing bridges in the country can provide valuable information to the decision-makers. This study focuses on the development of seismic fragility curve, which is the probability of exceedance of a defined damage parameter of the bridge pier under a given ground motion intensity and development of damage index function of bridge piers. Existing bridge piers are considered and peak ground acceleration is taken as ground motion intensity measure and drift at the pier top level is considered as the damage parameter.

Safety analysis for bridge pier under nearby road construction and operation

A temporary road underneath a riverine expressway was constructed to accommodate the need of transporting soil for land reclamation. One of the most outstanding characteristics of the new temporary road was that it passed underneath the piers of a continuous reinforced concrete bridge. The additional loads caused by the road construction and later on operation with heavy trucks potentially jeopardized the safety of bridges. The objective of this study was to examine the influence of the road construction and operation on the behavior of bridge piers and foundation piles. In addition, the effectiveness of a retrofit countermeasure of using steel sheet walls for improving the stability of the bridge was studied. A detailed three-dimensional finite element (FE) model, capable of addressing the interactions between pier columns, pile foundations, surrounding soils, and heavy truckloads, was developed to facilitate the analyses. After validating the model with the common analytical M method, the developed model was employed to investigate the behavior of bridge under the combined effects from temporary road loads (i.e., soil excavation load, pavement weight, and heavy truckloads). Field measured data from a tilt health monitoring system were utilized to verify the performance of FE analyses and confirm the performance of the retrofit countermeasure for pier deformation control. The steel sheet walls were found to be effective in increasing the safety of existing bridge piers.

Specialized strut-and-tie method for rapid strength prediction of bridge pier caps

Deep pier caps possess additional shear strength due to the formation of the strut action which cannot be captured by the traditional sectional method. The strut-and-tie method (STM) is a suitable method for capturing the deep beam action. The application of the STM, however, has many challenges including creating and optimizing a valid truss model, performing an indeterminate truss analysis, calculation of nodal and elemental stress limits, etc. The objective of this study is to explore innovative strategies to reduce the complexity of the STM by developing a strut-and-tie methodology to rapidly and accurately predict the shear capacities of deep pier caps. A graphical solution algorithm and associated computer code is developed to generate and analyze efficient strut-and-tie models while intuitively educating engineers in the correct use of the methodology. The accuracy of the methodology is assessed by modeling eight existing bridge pier caps with a general-purpose strut-and-tie method. In addition, nonlinear finite element analyses of the same pier caps are performed for an in-depth investigation and comparisons of the governing behaviors, strengths, and modes of failure with those obtained from the proposed methodology. Although not valid for deep beams, the sectional method calculations are performed to demonstrate the consequences of using it. The relationship between the shear span-to-depth ratio and the shear strength predictions from all three methods are compared for twenty-one regions. The proposed methodology has general applicability for modeling deep pier caps and is shown to provide similar modeling time and effort to the sectional method with accuracies comparable to those obtained from the nonlinear finite element analysis.

Experimental Study on the Seismic Behaviour of Reinforced Concrete Bridge Piers Strengthened by BFRP Sheets

With the continuous development of the ductility capacity concept for seismic design of bridges, the ductility capacity of many existing bridges does not meet the requirements of the current code for seismic performance because of the low reinforcement ratio and reinforcement corrosion of reinforced concrete (RC) piers. Because of their superior mechanical properties and low price, basalt fibre‐reinforced polymer (BFRP) sheets have potential application in the seismic retrofits field of existing bridges. To study the seismic strengthening effect of RC pier columns, scaled specimens with standard reinforcement ratios, with low reinforcement ratios according to the past code and with corroded reinforcements, were designed and manufactured and then wrapped and pasted with BFRP sheets on the plastic hinge areas. Pseudostatic tests were conducted to verify the seismic performance of the strengthened and unstrengthened specimens. Experimental results showed that the ultimate flexural capacity, deformation capacity, and energy dissipation capacity of strengthened RC pier columns were superior. Especially for strengthened specimens with low reinforcement ratios or corrosion reinforcement, their seismic performance could rival than that of columns with standard reinforcement ratios, which showed the advantage of BFRP sheets in the seismic retrofitting of existing bridge piers.

Study on seismic strengthening of railway bridge pier with CFRP and concrete jackets

Seismic strengthening is essential for existing bridge piers which are deficient to resist the earthquake. The concrete and CFRP jackets with a bottom-anchoring method are used to strengthen railway bridge piers with low reinforcement ratio. Quasi-static tests of scaled down model piers are performed to evaluate the seismic performance of the original and strengthened bridge pier. The fracture characteristics indicate that the vulnerable position of the railway bridge pier with low reinforcement ratio during earthquake is the pier-footing region and shows flexural failure mode. The force-displacement relationships show that the two strengthening techniques using CFRP and concrete jackets can both provide a significant improvement in loadcarrying capacity for railway bridge piers with low reinforcement ratio. It is clear that the bottom-anchoring method by using planted steel bars can guarantee the CFRP and concrete jackets to work jointly with original concrete piers Furthermore, it can be found that the use of CFRP jacket offers advantages over concrete jacket in improving the energy dissipation capacity under lateral cyclic loading. Therefore, the seismic strengthening techniques by the use of CFRP and concrete jackets provide alternative choices for the large numbers of existing railway bridge piers with low reinforcement ratio in China.

Scour Risk Analysis of Existing Bridge Pier Based on Inversion Theory

Scour around bridge piers might cause a decrease in lateral support at bridge foundations, and the simultaneous lateral loads would threaten the safety of existing bridges across rivers. Mitigation of foundation scour should be performed based on a comprehensive assessment of scour risk, combined with a thorough investigation of the uncertainties associated with the risk assessment procedure. However, in the commonly used risk assessment processes, identification of risk sources and determination of uncertainty propagation are based on experts’ experience. Moreover, the measured data from inspection of existing bridges cannot be fully utilized. In this paper, an inversion-theory-based method is proposed to evaluate the probability of risk events. First, risk sources were identified through an analysis of equations specified in Chinese bridge design codes. Based on the proposed method, prior information of the risk factors and measured scour data were taken into account, so that posterior distribution and statistical characteristics of the several risk sources could be obtained. Finally, the probability of risk events was determined and uncertainty propagation between risk sources and risk events revealed. To verify the proposed method and analyze the influence of prior information on the result, a case study was conducted and the information requirements of the method discussed.

Laboratory Tests and Numerical Simulations of CFRP Strengthened RC Pier Subjected to Barge Impact Load

Bridge piers are designed to withstand not only axial loads of superstructures and passing vehicles but also out-of-plane loads such as earthquake excitations and vessel impact loads. Vessel impact on bridge piers can lead to substantial damages or even collapse of bridge structures. An increasing number of vessel collision accidents have been reported in the past decade. A lot of researches have been conducted for predicting barge impact loads and calculating structural responses. However, in practice it is not possible to design bridge structures to resist all levels of barge impact loads. Moreover, with an increasing traffic volume and vessel payload in some waterways, the bridge piers designed according to previous specifications might not be sufficient to resist the current vessel impact loads. Therefore, strengthening existing bridge piers are sometimes necessary for protecting structures from barge impact. Carbon fiber reinforced polymer (CFRP) has been widely used in strengthening reinforced concrete structures under impulsive loadings. It is an effective material which has been proven to be able to increase the flexural strength of structures. In this study, CFRP composites are used to strengthen reinforced concrete piers against barge impact loads. Pendulum impact tests are conducted on scaled pier models. Impact force and pier response with and without CFRP strengthening are compared. The effectiveness of using CFRP strengthening the pier model is observed. In addition, numerical models of the bridge piers are developed and calibrated with experimental results. Parametric simulations of barge impacting on piers with or without CFRP strengthening are carried out. The results show that compared with unstrengthened pier, CFRP composite strengthened bridge pier has a higher impact resistance capacity and hence endures less structural damage under the same barge impact load. The effectiveness of CFRP strengthening with different CFRP thickness, CFRP strength and bond strength between the pier and the CFRP composite are also discussed.

Research on HGV Collisions with Concrete Bridge Piers

Bridge piers are highly vulnerable to accidental collision with heavy truck vehicles. Current design and assessment codes account the effect of vehicle collision by means of an equivalent static load. This methodology although is simple but have raised many concerns on their suitability to reflect the exact collision condition, which is highly dynamic. Therefore many existing bridge piers are in great danger of malicious impact. Recently, a research collaboration is initiated between JKR and UTP to investigate the impact vulnerability of RC bridge piers when subjected to HGV truck collisions. The work involves using nonlinear finite element (FE) simulation to conduct complex vehicle-pier impact scenarios. This paper is intended to present the general outlook plan of this project with emphasis focused on the consideration of FE models used for HGV trucks and concrete bridge piers.

Analysis of Dalian Subway Tunnel Shield Construction Impact with Engineering Materials and Engineering Mechanics on Existing Bridge Pier

In the 202 section of subway shield Dalian interval in close proximity to existing bridge as the basis, the surface settlement and bridge pier settlement observation station are established. By the 62 day of the crossing construction monitoring, the monitoring data are analyzed in detail. When surface subsidence induced by shield tunnel construction, above the measuring point start speed is faster than settling startup speed measuring points on both sides, about 2-2.5 times, subsidence range higher about 8 to 10 m ahead of time. Away from the pier side first started, and start faster than the side near the pier ,is about 1.2 times , settlement of shield construction are mainly concentrated in the distance before and after the excavation of shield machine 10 m, accounting for 80.72%-81.6% of the total settlement . At highest risk for shield construction area, we should strengthen monitoring and make contingency plans in a timely manner.

Non Destructive Testing of Bridge Pier - A Case Study

Abstract This paper reviews various NDT methods available and presents a case study related to the strength evaluation of existing bridge pier. The assessment of quality and strength is made by correlating the NDT observations with core tests. The assessment involves the core tests, Rebound hammer tests and Ultrasonic pulse velocity tests.

Evaluation of the Structural Integrity of Bridge Pier Foundations Using Microtremors in Flood Conditions

Bridge pier foundations occasionally become unstable due to scouring around piers in flood conditions, and operational restrictions imposed according to the water level are practical for maintaining safe train operation. However, when such restrictions are lifted, it is quite difficult to verify the condition of the bridge pier foundation. It is therefore necessary to develop a practical method of quantitatively evaluating and assessing the structural integrity of bridge pier foundations in flood conditions. This paper reports the results of analysis of long-term microtremor measurements made on existing bridge piers and a method to define the natural frequencies of bridges using microtremors.

Model Tests on Current Forces on a Large Bridge Pier Near an Existing Pier

A suspension bridge is being built over the Tacoma Narrows, Washington. The bridge will be placed on a structure mounted on two large concrete caissons, which will be exposed to strong currents. The piers are of rectangular section with chamfered edges in the upper portion. The caissons are being built at site while floating and moored in high currents. There are no known analytical methods or experimental data available on such structures at high Reynolds number. In order to determine the forces on the caisson due to current, a series of scaled physical model tests of one of the caissons was carried out. The forces on the caisson were measured in the presence of the existing bridge pier and the bottom contours of the Narrows were accurately modeled. The model scale was chosen as 1:100 and the tests were performed for the caisson at different drafts. This paper describes the test setup, and measurement system for a series of fixed caisson tests and demonstrates the consistency of the test data. The measured inline drag and transverse lift forces on the fixed caisson at different drafts are presented and the effect of the fluid velocity and flow vorticity on the frequency contents in the forces is discussed. The interaction effect of the neighboring existing pier on the current forces on the caisson is investigated. Since the measured forces were applied in the design analysis of the caissons, the scaling effect of the model test is also discussed. This paper is accompanied by two other papers, which form a group of three papers related to the project describing the current excitation on the caisson and the associated caisson responses. The other two papers in succession are by Chakrabarti et al. (J. Offshore Mech. Arct. Eng., to be published) and Chakrabarti and McBride (J. Offshore Mech. Arct. Eng., to be published). The paper by Chakrabarti et al. describes the numerical computation of the current forces on the caisson by a three-dimensional analysis, while the paper by Chakrabarti and McBride uses the information from these two papers to determine the motion response of the caissons and the mooring line tensions.

주철근 겹침이음된 실물 비내진 원형 교각의 내진성능평가

Most bridge piers were practically designed and constructed with lap spliced longitudinal reinforcing steels before the 1992 seismic design provisions of Korea Bridge Design Specification were implemented. It has been known that lap splice of longitudinal reinforcement in the plastic hinge region is not desirable for seismic performance of RC bridge piers. The objective of this research is to evaluate the seismic performance of existing circular reinforced concrete bridge piers by the Quasi-static test and to propose the need of seismic retrofit of existing bridge piers through the damage level. Test specimens were nonseismically designed with the aspect ratio 4.0 which could induce the flexural failure mode. It was confirmed from this experiment that significant reduction of seismic performance was observed for test specimens with lap spliced longitudinal reinforcing steels. Pertinent seismic retrofit was determined to be needed for existing RC bridge piers with the lap-spliced of longitudinal reinforcing steels.