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In this study, the results are presented and discussed from laboratory test campaigns specifically designed to investigate the behavior of sacrificial piles as a countermeasure against local scouring at a circular bridge pier and clear-water conditions with flow intensity slightly below the threshold of sediment motion. Sacrificial piles are assessed on the upstream side of the pier in two transverse and triangular arrangements. Piles can reduce scouring by deflecting the flow and creating a low-velocity wake region behind them. The efficiency of the piles against local scouring depends on the diameter of the piles, the number of piles, and the angle of the wedge. The investigation was aimed at evaluating the effectiveness of the sacrificial piles as a function of different dimensionless groups. It was found that the triangular arrangement of sacrificial piles has better results than the transverse arrangement. The results showed that the triangular sacrificial piles reduced the maximum local scour depth at the pier to 37.2% in the best configuration. Combined countermeasures were tested, which were composed of sacrificial piles and a bed sill downstream of the pier; in the best configuration, the scour depth reduction in front of the pier reached 51.1%. The increased efficiency of the combination of bed sill and sacrificial piles (BSSP) is an advantage that can reduce the risk of pier failure when the duration of the flood is short. This last result shows that a combination of BSSP may be a very effective countermeasure against local scouring at bridge piers. Finally, the coherent turbulent flow structure around the best combination of BSSP was investigated, and its effect on the bed scouring pattern was studied. A 3D analysis of the bursting process was used. Turbulence characteristics, as well as the occurrence and transition probabilities of bursting events, were calculated. The obtained results confirmed the quite effective effect of the combination of these two countermeasures in reducing the scour depth. [ABSTRACT FROM AUTHOR]

The present study investigated the influence of key design parameters on the seismic performance of prefabricated precast assembled piers' connection parts to better adapt to the industrialized construction of prefabricated precast assembled pier connected using grouting sleeves. Relying on a prefabricated assembled bridge in the actual project, the ABAQUS software was used to establish a refined solid finite element model of prefabricated assembled piers connected with grouting sleeves. Numerical simulation analysis was conducted for the piers with low circumferential reciprocating loading. The seismic performance of the prefabricated assembled piers was evaluated in terms of hysteresis characteristics, dissipation characteristics, and damage development. The effects of the length of the grouting sleeve and the diameter of the longitudinal reinforcement on the seismic performance were also investigated. The maximum error between the numerical simulation results and the test results was 5.7%, and the plastic region of the precast assembled pier obtained from the numerical simulation was consistent with the test results, indicating that the numerical simulation method is accurate and reliable. When the length of the grouting sleeve increased from 0.6 to 1.2 m, the yield load, peak load, and dissipation of energy of prefabricated assembled piers increased by 11.6%, 10.9%, and 11.4%, respectively; no significant change in residual displacement; ductility coefficient decreased by a small amount. When the longitudinal reinforcement diameter increased from 20 to 50 mm, prefabricated assembled piers yield load, peak load, and dissipation increased by 99.6%, 89.3%, and 218.9%, respectively, whereas the residual displacement increased by 137.3%, and the ductility coefficient decreased more. Increasing the length of the grouting sleeve or increasing the diameter of longitudinal reinforcement improved the stiffness of the piers, causing the piers to displace less and damage less under the same force, but the residual displacement would increase. [ABSTRACT FROM AUTHOR]

Various concrete bridges have been built across oceans, valleys, and mountains; however, the settlement displacement of bridge piers caused by environmental changes or self-weight during construction phases often leads to uneven stresses, cracking, and eventual collapse. To address the labor-intensive and high-cost issues of pier displacement monitoring using contact-type sensors, this paper proposes an automatic vision-based method for measuring pier settlement displacement under complex construction environments, such as complex image backgrounds, varying ambient light, and camera movement. In the proposed method, a deep learning network was first employed to eliminate the adverse effect of complex image backgrounds and varying ambient light on the accuracy of target detection; then, an adaptive displacement extraction algorithm without a human-computer interaction process was developed to automatically extract the center coordinates of targets attaching to the bridge piers and reference platform; finally, the pier settlement displacement was calculated by using the relative displacements obtained by a dual camera system to eliminate the measurement error caused by camera translation and rotation movements. Laboratory tests of a cantilever beam and field tests of a continuous multispan concrete girder highway bridge under construction have successfully validated the effectiveness and robustness of the developed methodology. The results obtained in this paper can provide some insights for engineers in applying computer vision technology for the real-time monitoring of bridge displacements. [ABSTRACT FROM AUTHOR]

In the Three Gorges reservoir area, the overhead upright pier is the primary structural form. For intelligent monitoring of existing terminals, this research chooses Chongqing Xintian Port as the study object and proposes a support vector machine (SVM) damage-inducing factor (DIF) inversion model based on particle swarm optimization (PSO). To apply the finite element method to analyze the stress distribution characteristics of quay pile groups under three main DIFs, including the stacking effect, ship impact load effect, and bank slope effect. After characterizing the stress data, it becomes evident that there exists a correlation between stress and each DIF parameter. Before generating the training sample set, principal component analysis is employed to reduce dimensionality and eliminate a substantial amount of redundant data. The model has an accuracy of 0.999 for the identification of the type of DIF and 0.975 for the identification of the location of the action of the DIF with F1 coefficients of 0.999 and 0.978, respectively. For the strength of DIF predictions, MAE and MSE were 4.871 and 1.202, respectively, R2 was 0.986, NSE was 0.986, WI was 0.996, and PBIAS was 0.095. After extracting every sample, the relative error for the ship impact load effect is 0.05, and the highest relative error for the bank slope effect is 0.02; the error for the stacking effect is limited to 0.08. The results suggest that the damage inducement inversion model of the SVM optimized by the PSO algorithm can effectively identify the DIF of the overhead upright pier. [ABSTRACT FROM AUTHOR]

Condition rating of bridges is specified in many countries since it provides a basis for the decision-making of maintenance actions such as repair, strengthening, or limitation of passing vehicle weight. In practice, professional engineers check the textual description of damages to bridge members, such as girders, bearings, expansion joints, and piers that are acquired from periodic inspections, and then make a rating of the bridge condition. The task is time-consuming and labor-intensive due to the large amount of detailed data buried in the inspection reports. In this paper, a natural language processing- (NLP-) based machine learning (ML) approach is proposed for automated and fast bridge condition rating, which can efficiently extract the information of deficiencies in bridge members. The proposed approach involves three major steps, say, data repository establishment, NLP-based textual data processing, and ML-based bridge condition rating prediction. The data repository is established with the inspection reports of 263 concrete bridges, and in total there, are four condition levels for the bridges. Then, the NLP-based textual data processing approach is implemented to calculate the word frequency and the word clouds to visualize the characteristics of bridges in different condition levels. Finally, four typical ML techniques are adopted to generate the predictive model of the bridge condition rating. The results indicate that the NLP-based ML prediction model has an accuracy of 89% and is very efficient so that it can be used for large-scale applications such as condition rating for regional-level bridges. [ABSTRACT FROM AUTHOR]

The well-known limitations of modal system identification methods have led to a broad exploration of alternative solutions for operational monitoring and damage diagnosis of structures. This study presents a time-domain Bayesian finite element model updating approach to jointly identify the vehicular loads and finite element modeling parameters of bridges using the vibration data and the location of vehicles traversing the bridge as input. A Bayesian model updating is devised and verified through a series of case studies based on numerically simulated data from a prestressed reinforced concrete box-girder bridge model. Damage states are defined for concrete degradation and delamination, steel corrosion, and loss of prestressing force. Ten different damage scenarios, encompassing the range from minor localized to major distributed damage, are examined. The responses of the damaged bridge are simulated under random traffic scenarios. The acceleration responses, along with the location of the vehicles on the bridge, are used for jointly estimating the model parameters and vehicular loads. The estimated model parameters are then used to infer the location and extent of damage within the bridge. The results show the successful performance of the proposed approach in a numerically simulated environment. [ABSTRACT FROM AUTHOR]

Vibration displacements are one of the most significant indicators in the health monitoring and condition assessment of bridges in the life cycle. The traditional monitoring means, such as contact sensors, have relatively high-cost and limited points for displacement measurement of bridges. This paper proposes a low-cost and non-contact monocular vision system based on the KCF algorithm to accurately and timely identify the vibration displacement of bridges. A conversion method associated with a scale ratio was established to cope with the loss of depth information in images when a monocular camera is used to monitor multiple targets in different depths of the field. A series of shaking table tests on a two-column pier with energy dissipation beams were conducted to verify the feasibility, accuracy, effectiveness, and robustness of the KCF-based identification approach. The results showed that the vibration displacements of the column identified by the monocular vision system based on the KCF algorithm are almost consistent with the measurement results obtained by the laser displacement sensors. The peak displacement discrepancies between both measurement methods are within 6% for all cases with different shaking amplitudes and earthquake waves. The RMSE of the displacement histories between both measurement methods is very low. The corresponding frequency spectra contents identified by the monocular vision system based on the KCF algorithm match well with the measurement counterparts recorded from the laser displacement sensors. [ABSTRACT FROM AUTHOR]

The continuous rigid structure bridge on both sides of the Quanzhou Bay Crossing Bridge uses double-limbed thin-walled flexible piers for the junction piers between the links, and the whole bridge has no bearings. In China, the monolithic bearing-free prestressed concrete continuous rigid-frame bridge is used in railway bridges. The junction pier between the two adjacent couplets is a double-leg thin-walled flexible pier. The single leg thin-walled pier is connected with half of the pier-top segment. During the construction process, the block with numbered zero on the top of the pier is temporarily anchored and connected. Symmetrical cantilevered baskets are used on both sides for construction, and after the mid-pier cantilevered construction is completed, the temporary anchoring device for the block with numbered zero is removed. Because the structural system conversion is required in the construction, the mechanical properties of the junction pier will change greatly before and after the conversion, so it is very necessary to calculate and analyze it to master. In this paper, the finite element model of the connecting pier is established accurately, the stress and deformation of each part of the connecting pier under unfavorable working conditions is analyzed in detail, the seismic spectrum analysis under the action of common earthquake and rare earthquake is carried out, and the stress and deformation law of the structure is expounded, which can provide some reference for the construction of similar projects in the future. [ABSTRACT FROM AUTHOR]

The hydrodynamic problems associated with the construction of the sea-crossing bridge were proposed. The deep-water approach bridge on both sides of the main bridge of Fuzhou Xiamen high-speed railway adopts the bearingless prestressed concrete integral rigid frame bridge for the first time in the domestic railway bridge design. The rigid frame bridge applies the hanging basket cantilever construction, and there are several options for closure. Because the bridge structure system changes before and after closure, which will cause the redistribution of bridge internal force, the results of internal force redistribution will be different with the sequence and position of closure, and sometimes, there will be great changes. In order to select the optimal closure scheme, this article establishes the finite element model of the whole bridge and analyzes the whole construction process according to the working conditions and the mechanical state of the bridge before closure is obtained. Based on this state, eight closure schemes are analyzed and studied, which provides a sufficient mechanical basis for the determination of the final closure construction scheme. [ABSTRACT FROM AUTHOR]

In this article, wrap rope connection device (WRCD), which considers the relative acceleration of piers and beam as a control variable, is proposed for improving the current situation of continuous girder bridges whose bearing force of a single pier is along the longitudinal direction and based on the synergy principle. The WRCD device, which meets the slow displacement requirements of temperature and vehicle load under normal operation, is implemented and used to improve the performance of the sliding bearing pier. During earthquakes, because of the amplification effect of the wrap rope, the instantaneous large stiffness state in the longitudinal force can be achieved. Based on the shaking table test of a typical continuous girder bridge for examining the performance of the WRCD during earthquakes, the dynamic characteristics, structural acceleration, displacement, and strain responses of the structure under different frequency spectra, and seismic input intensities are analyzed and the seismic reduction performance of the WRCD is demonstrated. This analysis demonstrated that, by activating WRCD, the ratio of the acceleration response of the fixed bearing pier to the sliding bearing pier increased from 10% to 57%; moreover, the force on each pier appeared more uniform. Furthermore, with an increase in the input intensity of the earthquake, the displacement of the primary beam and the seismic response of the fixed pier bottom considerably decreased and the synergy effect of each pier was more prominent. Under certain site conditions, the WRCD can effectively improve the synergy effect between the sliding bearing piers and fixed bearing pier; however, the improvement in the obtained result is directly associated with the seismic input characteristics. The design parameters of the WRCD should be determined as per different site conditions and the optimum application range of the WRCD. [ABSTRACT FROM AUTHOR]

Objectives. This study aimed to assess stress distribution in 5-unit fixed partial dentures (FPDs) with a pier abutment and rigid (RC) and nonrigid connectors (NRCs) with the canine rise and group function occlusal schemes by finite element analysis (FEA). Materials and Methods. In this FEA study, a geometrical model of the maxilla with natural teeth and periodontal ligament (PDL) was three-dimensionally designed and meshed by ANSYS and Pro/Engineer software programs. A 5-unit FPD was then designed to replace the lost first premolar and first molar teeth; the second premolar served as a pier abutment, and the canine and second molar served as terminal abutments. Two FPDs were designed with RC and NRC. Each FPD was analyzed with the canine rise and group function occlusal schemes (a total of 4 models). The first and second molars (180 N), premolars (120 N), and canine (80 N) teeth were subjected to progressive vertical and oblique (12-degree) loads, and maximum von Mises stress and strain in teeth and connectors were calculated for each model. Results. The models had 73704 elements and 137732 nodes. The connector design and occlusal scheme had significant effects on stress distribution in FPDs. The highest von Mises stress (73.035 MPa) was recorded in FPD with RC and group function occlusal scheme. The lowest von Mises stress (0.004 MPa) was recorded in FPD with NRC and canine rise occlusal scheme. Conclusion. Oblique forces created greater stress, and FPD with NRC and canine rise occlusal scheme decreased stress in FPD and increased stress in the tooth crown. [ABSTRACT FROM AUTHOR]

Predicting the bearing capacity of spread footings on aggregate pier-reinforced soil is particularly important for ground improvement. Various methods for predicting the bearing capacity of spread footings supported on aggregate pier-reinforced clay have been proposed. In addition, many fields or laboratory load tests have been conducted to identify the improvement effects of aggregate pier. However, no study has quantitatively compared the effect of the experimental scale on the prediction of bearing capacity. In this study, multiple linear regression analyses were performed for field and laboratory load tests, and the effects of the load test scale on bearing capacity prediction were identified. The sensitivity analysis showed that the prediction model for the laboratory load test (MLRL) exhibited a higher sensitivity for the undrained shear strength than that of the field load test model (MLRF). However, the sensitivity of the area replacement ratio of MLRL was less than half that of the MLRF. As the undrained shear strength increased, the predicted bearing capacity of the MLRL was larger than that of the MLRF owing to the influence of boundary conditions on the experimental equipment. [ABSTRACT FROM AUTHOR]

To improve the resilient capability of bridges, a novel multi‐stage superelastic variable stiffness pendulum isolator (SVSPI) is developed by incorporating superelastic shape memory alloy (SMA) with the multi‐stage variable stiffness pendulum isolator (VSPI), which featured with the favorable adaptability under service conditions and near‐fault excitations. Based on OpenSees platform, the numerical model for novel multi‐stage superelastic variable stiffness pendulum isolator is created. A fractional factor based design method is suggested for parameter optimization of the multi‐stage superelastic variable stiffness pendulum isolator. The example bridges with the novel isolators are designed to conduct the seismic mitigation investigation under near‐fault earthquakes. The effectiveness of the novel superelastic multi‐stage variable stiffness pendulum isolator and suggested design method is further discussed by case study. Results show that the novel multi‐stage superelastic variable stiffness pendulum isolator designed by the proposed fractional factor based design method can perform the dual control of the isolator residual displacement, girder displacement, and base forces in piers for bridges. The effectiveness of the multi‐stage superelastic variable stiffness pendulum isolator with the optimal parameters is demonstrated by case study. The technical achievements can provide reliable basis for structural resilience enhancement and potential structural applications. [ABSTRACT FROM AUTHOR]

Based on the design concept of earthquake-resilient structure, a new-type of box-shaped steel piers with embedded energy-dissipating steel plates was proposed. Quasi-static tests of 6 box-shaped steel pier specimens under variable axial pressure and cyclic horizontal loading were carried out. By analyzing the failure mode, load-displacement hysteretic curve, skeleton curve, displacement ductility coefficient, stiffness degradation characteristics, strength degradation coefficient, and cumulative hysteretic energy, the effects of setting energy-dissipating steel plate, axial compression ratio, and thickness of energy dissipation steel plates on the seismic performance of new-type steel piers were discussed. Finite element models of steel bridge piers were established and compared with the test results. The analysis results using FEM agree well with the test results. Results show that the setting of energy-dissipating steel plates can effectively improve the ductility, deformation capacity, and energy-dissipating capacity of box-shaped steel piers, and effectively delay buckling deformation and cracking of wall plates. The steel plate near the bolt hole of the wall plate at the root of the new-type of box-shaped steel piers is easy to crack due to stress concentration, resulting in a rapid reduction of the maximum bearing capacity of the specimens. With the increase of axial compression ratio, the bearing capacity, energy-dissipating capacity, and earthquake-resilient capacity of the specimens increase. The smaller the thickness of the replaceable energy-dissipating steel plates, the smaller the bearing capacity and faster the stiffness degradation of the specimens become, while the ductility and energy-dissipating capacity of the specimens are improved. The axial compression ratio and the thickness of the energy-dissipating steel plate have relatively little effect on the strength degradation of the specimens. In order to facilitate the popularization and application of the new-type steel piers, formulas were also established to calculate the bearing capacity and displacement ductility factor of the new-type of box-shaped steel piers. [ABSTRACT FROM AUTHOR]

To calculate the influence of pier size on the pier failure mode, a double-span continuous girder bridge model was selected for analysis. The transient wave function expansion method was used to calculate the excitation conditions required for pier separation and the limit solution of pier longitudinal deformation under pier separation, and the indirect mode superposition method was used to calculate the vertical impact force of the pier-beam. The calculation results show that the higher the pier height, the smaller the section size, the larger the vertical seismic acceleration required to separate the pier-beam, the smaller the vertical contact force of the pier-beam, and the larger the most unfavorable value of the longitudinal deformation of the pier caused by separation. The stress of the bridge pier before and after separation is compared and the influence of separation on the failure of the bridge pier is put forward. The study shows that when pier and beam separation occurs, there may be multiple failure modes superimposed on the pier, and the first failure mode will have variation with the change in pier size. [ABSTRACT FROM AUTHOR]

Summary: Structural health monitoring (SHM) is one of the main research topics in civil, mechanical and aerospace engineering. In this regard, modal parameters and their trends over time can be used as features and indicators of damage occurrence and growth. However, for practical reasons, output‐only techniques are particularly suitable for the system identification (SI) of large civil structures and infrastructures, as they do not require a controlled source of input force. In this context, these approaches are typically referred to as operational modal analysis (OMA) techniques. However, the interpretation of the OMA identifications is a labour‐intensive task, which could be better automated with artificial intelligence and machine learning (ML) techniques. In particular, clustering and cluster analysis can be used to group unlabelled datasets and interpret them. In this study, a novel multi‐stage clustering algorithm for automatic OMA (AOMA) is tested and validated for SHM applications—specifically, for damage detection and severity assessment—to a masonry arch bridge. The experimental case study involves a 1:2 scaled model, progressively damaged to simulate foundation scouring at the central pier. [ABSTRACT FROM AUTHOR]

Bridge pier scour engendered by typhoons or flooding poses a threat to the stability, bearing capacity, and other performance parameters of bridge foundations. In traditional static evaluation procedures, linear force distributions are used to express the fluid behavior under current forces, which results in overestimation of stability. A finite element simulation was conducted in this study to correctly evaluate the effect of fluid by developing a fluid-solid interaction (FSI) system. In the FSI system, simulation results for both the fluid and solid systems were exchanged. Thus, the force generated by the fluid system could be incorporated into the solid system to estimate the dynamic response of a pier. A scaled single-pier scour test was first conducted numerically and experimentally. The results showed that the established FSI system can consider the fluid-solid interaction and reflect pier scour behavior accurately. To test the validity of the proposed system, the scour process was numerically conducted on an engineering bridge. Two safety factors were proposed to evaluate the stability of the bridge structure under extreme events such as rainfall or typhoon. The result has proven that the scour stability of the bridge pier can be appropriately evaluated by the proposed system. [ABSTRACT FROM AUTHOR]

The self-anchored suspension bridge is a kind of the flexible and redundant structural system. For this type of bridge, the current code only gives the overall seismic design principle, and there is little research on seismic fragility in the existing literature. Taking the three-tower self-anchored suspension bridge as the research object, the finite-element dynamic models with and without damping are established, respectively. Based on the strong earthquake database of PEER (Pacific Earthquake Engineering Research), 10 ground motion records are selected, and the seismic fragility curves of piers, bearings, towers, and slings are established by using the incremental dynamic analysis (IDA) method. The fragility curves of the bridge system were established by first-order reliability theory. In this study, the damage probability of bridge components under a seismic wave is studied. The results show that the damage exceedance probability of the damped connection system is reduced compared with the undamped fully floating structure system under the action of seismic waves. The damper device makes the seismic performance of the structure significantly improved, and the reduction effect of the damper device on high-intensity earthquakes is more obvious than that on low-intensity earthquakes. [ABSTRACT FROM AUTHOR]

Based on the project sea area where the large-scale sea-crossing bridge is located, the marine environment is facing the threat of severe marine environmental issues such as strong typhoons and big waves. In order to resist the impact of the super wave load, the research focuses on a new structure derived from soft computing techniques in a simulated environment. Since the conventional methods cannot be used for handling such an important problem, soft computing techniques can certainly help to provide simulated solutions. These solutions can be exploited in a real-time environment to test their viability. The overall physical model test of the wave with a scale of 1 : 40 is carried out in this research study by using the proposed methodology. By setting a series of groups such as different wave height, period, water level (pier foundation scouring depth), and wave-current coupling, it is studied that the wave height and period are in positive proportion to the wave force on the pier column structure. However, there is no obvious relationship with the water level change (scouring depth). The buoyancy of the pile cap structure is about 1.27 times greater than that of the pier structure. Compared with the combined wave force of the single wave and wave current, the sensitivity and the relationship have been studied. Using this study and several engineering results completed in the early stage and also verified by the measured data, the results show that the proposed soft computing technique has good accuracy and can provide a reference for the load estimation of large-scale foundation structures. [ABSTRACT FROM AUTHOR]

The study aims to further standardize the construction process, improve the construction quality, and ensure the stability of infrastructure construction. The continuous rigid-frame bridge is taken as the research object, the finite element model of the bridge body is established by using the beam element, and the overall stability of the rigid-frame bridge is analyzed in the construction and completion stages. Moreover, the stability coefficient and buckling mode are established under different working conditions in each stage, the linear stability variation law is summarized, and the geometric nonlinear stability analysis method is established through the specific data. The nonlinear stability safety factor and buckling mode are obtained, and the influence of wind load and initial defects on the stability of continuous rigid-frame bridge is further explored. The results show that with the increase of the bridge height, the overall stability factor of the bridge is decreasing, and the safety factor of the single-limb thin-walled hollow pier is relatively larger than that of the double-limb thin-walled hollow pier. During the construction, the asymmetric self-weight load caused by the asynchronous load and cantilever pouring has the greatest impact on the stability of the bridge. The stability safety factor of the geometric nonlinear stability analysis method constructed is 0.3% and 1.27% lower than the ideal state, respectively. The stability safety factor of the wind load and the initial defect is 12.65% lower than the ideal state, and the stability safety factor is greatly reduced. The results have important reference significance to ensure the construction safety and overall stability of the bridge. [ABSTRACT FROM AUTHOR]

Concrete continuous rigid-frame bridges are the most commonly used to cross exciting highway and railway. Before the bridge closure, the closure jacking force (CJF) needs to be determined firstly, which plays an important role in mid-span deflection controlling and the whole bridge stress state. This study proposed a closure jacking force calculation algorithm for curved prestressed concrete continuous rigid-frame bridges with asymmetric cantilevers and piers. Firstly, the mechanics method was used to analyze the relationship between the CJF and normal stress of main-girder and the pier. In addition, an actual bridge was taken as a numerical simulation case to determine the influence of the deformation and the stress induced by concrete shrinkage and creep of the main-girder and the jacking force. Finally, in order to obtain the optimal stress state of bridge piers, the multi-objective linear programming method was proposed to calculate the CJF. The results show that curved prestressed concrete continuous rigid-frame bridges usually suffered longitudinal and transverse bending and torsion under the concrete shrinkage and creep of the main-girder and the CJF, and the CJF significantly affected the normal stress of the pier with a low anti-push rigidity. The normal stress of piers was obviously linear with the CJF during whole construction and operation state of bridges at the following three states: the jacking process, bridge completion, and ten years of bridge operation. The multi-objective linear programming algorithm was an effective way to determine the optimal CJF and can fully reflect both longitudinal and transverse bending of piers. [ABSTRACT FROM AUTHOR]

Vehicular impact on bridge piers is one of the leading causes of bridge failure. Due to the increase in vehicle-pier collisions, many researchers have studied the performance of RC bridge piers under vehicle collisions. Adding steel fiber is an alternative way to improve the impact resistance of concrete structures and enhance their capacity for energy absorption. However, a study on the performance of piers with steel fiber-reinforced concrete under impact load is limited. This study examines the performance of steel fiber-reinforced concrete (SFRC) bridge piers subjected to impact loading. To study the impact behavior of SFRC piers, a numerical model of bridge piers with impact mass was developed by LS-DYNA. The reliability of the numerical analysis was validated. To investigate the effects of impact mass, impact velocity, the volume of steel fiber, concrete grade, and percentage of longitudinal reinforcement on the impact behaviors of piers and the impact forces, parametric studies were carried out. The finite element analysis revealed that the addition of steel fiber resists lateral deformation and significantly affected the failure modes of bridge piers under impact loading. Moreover, the deformation of the impacted piers and the impact force is mainly affected by the addition of steel fiber, impact energy, and percentage of longitudinal reinforcement and is not sensitive to concrete strength. [ABSTRACT FROM AUTHOR]

Precast technology is increasingly favoured by bridge engineers, and the seismic performance of precast bridge piers urgently needs to be addressed. Precast piers have a complex load-bearing mechanism, and their design method has not been clearly determined. Fibre plastic hinge theory can satisfactorily analyse the seismic performance of precast piers. In this study, the seismic performance of precast piers is analysed through numerical simulation of pier columns based on the pseudostatic testing of a set of existing precast piers and combined with fibre plastic hinge theory. The results show the following: With reasonable constructional measures, precast piers connected by grouted sleeves indeed have seismic performance similar to that of cast-in-place components. Finite-element programs can be employed to simulate the mechanical properties of steel rebars before yielding well but not those after yielding or under fatigue. When fibre plastic hinges are used for finite-element analysis, if the fibre cross-section is reasonably divided, the length of the plastic hinge has little influence on the results; otherwise, too densely distributed plastic hinges may lead to nonconvergence of the results in a later working condition. The plastic hinge method recommended in this paper, especially the sectional fibre-cross-section division method, can obtain the plastic hinge performance state, it can help save the test cost and make up for the shortage of test data. [ABSTRACT FROM AUTHOR]

A three-dimensional finite element analysis was carried out for the influence of soil-structure interaction (SSI) on the seismic response of an isolated continuous bridge with a friction pendulum system (FPS). SSI was modelled using the soil resistance vs deflection nonlinear springs (following p-y curves). The influence of SSI on the dynamic behaviour and the seismic response of isolated bridges with different friction coefficients of FPS were investigated using six measured ground motions. Results show that the effect of SSI is limited on the isolation period of the bridge, but significant on the response amplitude of the bridge structures, and particularly on the response amplitude at the pier top and bottom. The displacement and acceleration at the pier top are underestimated, while the shear force and bending moment at the pier bottom are overestimated if the SSI effects are ignored, which suggests that SSI should be considered in the seismic analyses of continuous bridges. [ABSTRACT FROM AUTHOR]

Rigid frame bridges with different heights of adjacent piers are inclined to crack the main girder at the pier-beam connection. This cracking occurs due to a significant difference in thrust stiffness between tall and short piers. This problem can be resolved by applying ultra-high performance concrete (UHPC) materials. Thus, in the present paper, the seismic performance and failure behavior of UHPC thin-walled short piers were tested under low-frequency cyclic loads. Based on previous studies, the test was conducted using a proposed experimental model, where the effects of longitudinal reinforcement ratio, stirrup reinforcement ratio, and axial load ratio were considered. The failure mode, ultimate bearing capacity, stiffness, displacement ductility factor, and other performance parameters were analyzed. It was found that the specimens present the bending-shear failure mode. Also, the load-bearing capacity of the UHPC thin-walled piers was significantly improved by increasing the longitudinal ratio of the thin-walled short piers, while the contribution of the stirrup ratio was limited. In addition, compared with traditional short piers, the ductility of UHPC thin-walled short piers increased by 53.36%, and the thrust stiffness decreased by 23.73%, indicating that UHPC thin-walled short piers have more efficient seismic performance than RC short piers. Note that, in the present paper, UHPC thin-walled short piers' internal behavior was also analyzed by establishing a finite element model. The analysis proves that the numerical results are consistent with the experimental data, which is promising to better understand the failure behavior. [ABSTRACT FROM AUTHOR]

In order to research the force state of the piers subjected to a ship collision under the protection of floating anti-collision facilities, this study uses nonlinear spring connections to simulate the impact of ship damping and incidental water quality in the collision area. BIM technology is used to realize a safety evaluation method for the anti-collision floating box protection when the ship is colliding with piers. Established a BIM-based parametric preprocessing model for ships, piers, and anti-collision facilities, and opened the interface with ABAQUS longitudinally. After realizing the parameter adjustment of the BIM model, the visual parameter adjustment can be realized without destroying the boundary conditions, load conditions, and meshing. Taking a rigid frame bridge as an example, the most disadvantage position of the bridge pier under ship collision is determined by the parameterization method. At the same time, multi-condition analysis was carried out on the ship impacting the pier anti-collision floating box at different angles, different tonnages, and different speeds. Finally, the analysis results are traced back to the BIM model, achieving the unified integration of BIM model information and finite element analysis results and the purpose of visual analysis of any working conditions. The results show that the use of BIM parameterization technology to achieve linkage with the finite element preprocessing model can improve the efficiency of multi-condition sensitivity analysis and achieve the purpose of visual dynamic adjustment. The safety assessment analysis of the pier under the protection of the anti-collision pontoon on the pier under various working conditions shows that the anti-collision pontoon effectively reduces the hazard of the ship colliding with the pier, and the impact force gradually increases with the change from the oblique collision to the frontal collision. The peak impact force increases with the weight of the ship and shows a nonlinear relationship, such that the peak value of impact force increases with the speed increase, and the speed and the peak values of impact force show basically a linear relationship. [ABSTRACT FROM AUTHOR]

Offshore bridges may suffer from chloride ion corrosion, tsunami wave impact, and earthquake. However, the coupling effects of multiple factors have not been fully considered. This paper studied multiple degradation effects on the seismic performance of offshore piers considering tsunami wave impact, chloride ion corrosion, and their interaction. Firstly, through the scale model test of tsunami wave flume, the wave force of box girder structures and piers under different tsunami wave conditions is measured. Then, according to the corrosion characteristics of coastal chloride salts on reinforced concrete bridge piers, the corrosion parameters is selected by Latin hypercube sampling, and the influence of corrosion expansion and cracking of bridge pier cover on the chloride ion corrosion process is considered to modify the degradation model of corroded reinforced concrete materials. Finally, the wave load measured by the test is converted by the similarity criterion of the fluid mechanic test and loaded into the ABAQUS full-bridge model, and the pier after the tsunami wave is evaluated by the pushover analysis. The bearing capacity and lateral stiffness of the corroded pier before and after different tsunami waves are compared. The results show that the lateral bearing capacity and stiffness of bridge piers are, respectively, decreased by 27.6% and 6.2% after 30 years of service. Without corrosion, the lateral bearing capacity and stiffness of piers were, respectively, reduced by 11.45% and 10.6% after HXB-5 wave impact. After 30 years of service, the lateral bearing capacity and stiffness of bridge piers are, respectively, reduced by 41.8% and 22.5% under the combined action of corrosion and HXB-5 wave impact. It is found that the coupling effects of multiple degradation factors were more significant than the simple superposition ones. Therefore, the coupling effect of multiple factors should be considered in practical engineering. [ABSTRACT FROM AUTHOR]

In order to reduce the local scour before the antiscour device of piers, this paper proposed an improvement on a "V-type" device. That was to say, wing plates were set on the surface of the "V-type" device to enhance the diversion and reduce the local scour. To explore the protection effect of the modified device, the inclination angles of the wing plates were set to three angles, and the scour characteristics around the device were studied through the flume scour test and numerical simulation test. The results showed that the wing plates can reduce the impact force of the diving flow which was at the front end of the protective device. Besides, they could also disturb the flow around both sides of the device and weaken its sediment carrying capacity. Thus, the local scour around the device was effectively reduced. Especially, when the wing plates were 30°, the performance of reducing the local scour was the best. [ABSTRACT FROM AUTHOR]

In this study, the lateral impact tests of six RC piers which were protected by closed-cell aluminum foam (CCAF) were carried out by making use of an ultrahigh drop hammer horizontal impact test system. The protective effects of CCAF with different densities on the piers were then analyzed. The data regarding the piers' impact force, displacement, reinforcement strain, and crack and damage development were mainly collected during the experimental testing processes. The results indicated that, when the impact energy was less than 7258 J and the density of the CCAF was 0.45 g/cm3, the cumulative impact force and displacements of the piers decreased by 67% and 35%, respectively. Therefore, it was considered that the CCAF with a density of 0.45 g/cm3 had displayed the best protective effects at that stage. It was also observed that when the impact energy was greater than 7258 J and the density of the CCAF was 0.55 g/cm3, the cumulative impact force and displacements of the piers decreased by 25% and 18%, respectively. Therefore, the CCAF with a density of 0.55 g/cm3 had displayed the best protective effects at that stage. Furthermore, under the conditions of constant accumulative impact energy, the protective effects of CCAF on the piers were observed to be weakened if it entered the densification stage too early and high-yield platforms were formed due to the density levels becoming too high. However, it was found that reasonable density and thickness increases could effectively delay the entry of CCAF into the densification stage, which effectively reduced the shearing effects which occurred when the impact speeds were too high, thereby preventing the shear failure of the piers. [ABSTRACT FROM AUTHOR]

This study investigates the influence of auxiliary piers on the natural frequency, deformation characteristics, displacements of the related parts, and internal forces of a long-span heterogeneous steel-structured main tower cable-stayed bridge. Taking the Guohe Third Bridge in Anhui Province as an example, the software ANSYS was used to establish a three-dimensional finite element model of a cable-stayed bridge, and the dynamic characteristics of a long-span specially shaped hybrid steel structure main tower cable-stayed bridge with auxiliary piers added to single span and double spans were analysed. The results show that when one or three pairs of auxiliary piers are added to a single span, the changes in the natural frequency and deformation characteristics are smaller than those when there are no auxiliary piers. When one or three pairs of auxiliary piers are added to each of the two spans, the natural frequency and deformation characteristics are relatively low. Auxiliary piers induce relatively large changes; the changes with 3 pairs of auxiliary piers for a single span is compared with those with 1 pair for a single span, and 3 pairs and 1 pair of auxiliary piers are added to both spans for comparison. The natural vibration frequency and deformation characteristics exhibit relatively small changes; the presence or absence of auxiliary piers and the number of auxiliary piers have a greater influence on the vertical displacement of the main girder and less influence on the vertical displacement of the main tower. An appropriate number of auxiliary piers are beneficial to the seismic resistance of a cable-stayed bridge, and if the number of auxiliary piers is too large, the seismic capacity of the bridge is reduced; it is recommended that a pair of auxiliary piers be added to both spans to optimize the overall dynamic performance of a cable-stayed bridge. This research method can be used on similar cable-stayed bridges to optimize their dynamic characteristics by setting a certain number of auxiliary piers. [ABSTRACT FROM AUTHOR]

Collision on reinforced concrete (RC) piers by moving vessels or vehicles is a significant issue. This paper presents the static and impact behavior of RC piers with different hollow ratios. Three specimens were statically tested to obtain the load-displacement response. Low-velocity collision on eleven RC piers was conducted under the same velocity of 2.42 m/s. The damage process, failure mode, and force response were comprehensively analyzed. The experimental results indicate that the hollow ratio plays a significant role in the failure mode and ultimate load of RC piers under static and impact loadings. For RC piers with a hollow ratio of 0 and 0.4, the global failure dominated the damage process. However, failure of piers with a hollow ratio of 0.6 was governed by the local damage near the loading point. The static load capacities of the RC piers with a hollow ratio of 0.4 and 0.6 were 1.27% and 60.5% smaller than that of the solid pier, respectively. RC piers with a higher hollow ratio or lighter drop weight suffer smaller peak impact force. The increase of the longitudinal reinforcements leads to a promotion of the peak and mean impact force. Furthermore, the numerically predicted failure modes and impact load response show satisfactory agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Bridges in a marine environment have been suffering from the chloride attack for a long period of time. Due to the fact that different sections of piers may be exposed to different conditionals, the chloride-induced corrosion not only affects the scale of the deterioration process but also significantly modifies over time the damage propagation mechanisms and the seismic damage distribution. In order to investigate the seismic damage of existing RC bridges subject to spatial chloride-induced corrosion in a marine environment, Duracrete model is applied to determine the corrosion initiation time of reinforcing steels under different exposure conditionals and the degradation models of reinforcing steels, confined concrete, and unconfined concrete are obtained based on the previous investigation. According to the seismic fragility assessment method, the damage assessment approach for the existing RC bridges subject to spatial chloride-induced corrosion in a marine environment is present. Moreover, a case study of a bridge under two kinds of water regions investigated the influence of spatial chloride-induced corrosion on the seismic damage of piers and other components. The results show that the spatial chloride-induced corrosion may result in the section at the low water level becoming more vulnerable than the adjacent sections and the alteration of seismic damage distribution of piers. The corrosion of pier will increase the seismic damage probability of itself, whereas it will result in a reduction of seismic damage probability of other components. Moreover, the alteration of seismic damage distribution of piers will amplify the effect. Due to the fact that the spatial chloride-induced corrosion of piers may alter the yield sequence of cross section, it then affects the seismic performance assessment of piers. A method to determine the evolution probability of yield sequence of corroded piers is proposed at last. From the result, the evolution probability of yield sequence of piers in longitudinal direction depends on the relationship between the height of piers and submerged zone. Moreover, the height of piers, submerged zone, and tidal zone have a common influence on the evolution of yield sequence of piers in transversal direction. [ABSTRACT FROM AUTHOR]

Pounding may occur between the main girders under the action of strong earthquakes, so as between main girders and abutments. This causes excessive longitudinal displacement of the main girder and unseating damage to bridges. Because long bridges in mountainous areas with high intensity are easy to unseat, the authors studied the influence of restrainer piers, expansion joint spacings (EJSs), and the span on the seismic performance of long bridges. The ABAQUS finite element software was used to simulate a bridge dynamic analysis model considering the elastoplasticity of the pounding effect of the pier and the beam. By inputting El-Centro, Northbridge, and Taft seismic waves, the time-history analysis of the seismic response of long bridges was carried out. The results indicated that a reasonable number of restrainer piers, an appropriate EJS, and a span could effectively reduce the maximum relative displacement of pier-beams. This behavior will improve the seismic performance of bridge structures. Moreover, for a 24-span equal-height beam bridge, the optimum seismic effect was obtained when 3 restrainer piers, an EJS of 70 mm, and a 50 m span were used. [ABSTRACT FROM AUTHOR]

The non-uniform stratum and uneven surface have the complicated seismic spatial variability. The seismic response of high pier and small radius curved bridge caused by the seismic specificity of this kind of terrain has not been systematically studied. According to the multi-point excitation theory of long-span structures and the similar theory of shaking table test in model structures, a high pier with small radius curved girder bridge was used as the research object. The shaking table test of real bridge model was carried out to study the seismic response laws of this kind of bridge under multi-point excitation. The results show that the designed seismic wave expansion device can meet the test requirements. The frequency of the model structure decreases rapidly and the damping ratio increases during the whole test process. The local terrain effect amplifies the seismic response of high pier and small radius curved bridge. The seismic response of high pier and small radius curved bridge is affected by different frequency spectrum seismic waves, and there is a big difference. Based on the above results, the impact of multi-point excitation should be considered in seismic design of high pier with small radius curved bridge. [ABSTRACT FROM AUTHOR]

To explore the rectification parameters of the diversion piers optimized for the forebay of the pump station with a lateral angle of 45°, the orthogonal experiment and computational fluid dynamics methods are used to analyze the flow characteristics of the diversion piers under different parameter combinations. The flow pattern in the forebay of the side water inlet is improved. The rectification effect of the diversion piers under 16 schemes is analyzed, considering the length, width, radian, and relative height of the diversion piers. Combined with numerical simulation, a better rectification scheme is provided, and finally, a reasonable range of values for the rectification parameters of the forebay diversion pier of the side 45° bend angle pump station is obtained. [ABSTRACT FROM AUTHOR]

In this paper, a risk-based multiobjective optimal seismic design method for reinforced concrete (RC) piers is proposed. This method is used to determine the size and reinforcement ratios of piers to minimize the seismic risk of bridge systems and the construction cost of piers. The Pacific Earthquake Engineering Research- (PEER-) based probabilistic seismic risk assessment approach and the response surface method (RSM) are adopted to develop the seismic risk response surface model, which represents the relationship between the design parameters of piers and the seismic risk of bridge systems. The Pareto optimal solutions of piers are determined by applying an improved version of the nondominated sorting genetic algorithm (NSGA-II). As a case study, the proposed optimal seismic design method is applied to a continuous concrete box girder bridge. The optimal design schemes of piers according to two strategies are determined from the Pareto optimal solutions. The results show that the seismic risk response surface model can be used to accurately describe the relationship between the design parameters of piers and the seismic risk of bridge systems. The case study demonstrates the effectiveness of the proposed optimal seismic design method. The analysis of the Pareto optimal solutions allows designers to more rationally conduct the seismic design of piers. [ABSTRACT FROM AUTHOR]

This paper introduces the structure and principle of a new isolation device—rebar isolation pier—which is mainly composed of vertical steel bar and asphalt ointment. It is used to reduce the earthquake action of the building structure. Compared with other isolation devices, the rebar isolation pier has the following advantages: simple structure, convenient construction, low cost, simple maintenance, and easy to fetch material. In the experiment, the test model is a two-layer frame, and the Taft wave and the Wolong wave were selected to simulate the actual earthquake. In order to study the damping effect of asphalt ointment, two different isolation piers (filled and unfilled with asphalt ointment) were included. The dynamic characteristics and isolation effect of the rebar isolation pier are studied by analysis of acceleration, displacement, and hysteresis loops. At the same time, according to the principle of energy method, the energy balance equation of the rebar isolation pier was proposed, and the total input energy and damping energy are used to analyze the energy of the isolation pier. The results demonstrate that the rebar isolation pier can effectively reduce the natural frequency, acceleration response, and absorbed seismic energy of the structure when the peak ground acceleration reaches 0.3 g, and it still has the potential to withstand greater seismic action. [ABSTRACT FROM AUTHOR]

In the present study, in order to examine the impact performances of ordinary reinforced concrete bridge piers which have been replaced by stainless-steel bars of equal cross-sections under the protective condition of anticollision material, the impact dynamic responses of the ordinary reinforced concrete bridge piers, with replacements under the protection of closed-cell aluminum foam, were compared and analyzed using an ultrahigh drop hammer impact test system. The results showed that when the impact velocity was small (for example, less than 1.42 M/s), after the implementation of equal cross-sectional replacements, the closed-cell aluminum foam had been in an elastic or yield stage. During that stage, the impact forces of the stainless-steel reinforced concrete piers were larger than those of the ordinary reinforced concrete piers, and the relative ratios were stable at approximately 28 to 34%. In addition, the relative ratios of the displacements at the tops of the components were also found to be stable at approximately 22%, and the change rates of the concrete ultrasonic damages were approximately the same. However, when the impact forces had increased (for example, more than 1.67 m/s), the closed-cell aluminum foam entered a densification stage, and the peak impact force ratios decreased sharply. It was also observed that the relative peak displacement ratios at the tops of the components displayed increasing trends, and the change rates of the concrete ultrasonic damages had displayed major flux. Therefore, the replacement of the ordinary piers with stainless-steel bars had increased the possibility of shear failures. [ABSTRACT FROM AUTHOR]

The main function of pier is to transmit the load from superstructure to foundation reliably. Under earthquake action, the main failure reason of bridge is the damage of bridge pier. The application of some high-performance materials is helpful to improve the seismic performance of bridge piers. Based on seismic vulnerability analysis, this paper studies the feasibility of using engineered cementitious composite (ECC) and high-strength bars in bridge piers. Taking a rigid pier as an example, a nonlinear numerical model is established by OpenSees software. The reasonable replacement height of ECC in plastic hinge regions, stirrup ratio of pier section, and replacement rate of high-strength bars are obtained through the seismic performance analysis of the pier. Then, seismic vulnerability of rigid pier with ECC and high-strength bars is analyzed. The results show that it is feasible to improve the seismic performance of the piers by using ECC and high-strength bars. Considering the economic rationality, the replacement height of ECC in plastic hinge regions can be determined according to the curvature change point. For the rigid pier, the economical and reasonable volume stirrup ratio is 0.78%. The ultimate curvature of RC/ECC pier bottom increases by 12.4% when the longitudinal bars of the pier are replaced by high-strength bars, and the energy dissipation capacity increases by 22.5% on average. Compared with the pier's original design, the exceedance probability of each limit state of the rigid pier with ECC and high-strength bars is significantly reduced. Its seismic performance is superior, and the risk of seismic damage is significantly reduced. [ABSTRACT FROM AUTHOR]

At present, most of the research studies on the seismic performance of the durability degraded reinforced concrete structure only consider the influence of a single factor. This paper comprehensively considers the factors such as concrete carbonization, steel corrosion, and bond slip performance degradation caused by other durability factors and durability damage repair and studies the influence of the above factors on the seismic performance of bridge structures. Based on the finite element model considering the bond slip and the material parameters of time-varying durability damage, the seismic performance analysis model of the pier is established considering material durability damage repair in different service periods. Then, the effect of material durability damage repair on the seismic performance of the pier is examined. The results show that the displacement of the pier top increases, the curvature of the pier bottom decreases, and the moment-curvature curve pinching phenomenon is further evident when considering the bond slip. When considering the durability damage repair of materials, the curvature considerably decreases (the maximum value is approximately 16.04%) with the extension of the service time of the bridge, and the pier damage is substantially reduced. [ABSTRACT FROM AUTHOR]

To rapidly restore the seismic behaviour of a portal steel bridge column after an earthquake, the installation of replaceable tubular steel piers at the root of a portal steel bridge column is proposed herein. In this study, various tubular steel piers with different structural measures were designed; an axial compression test and a numerical simulation of the newly designed tubular steel piers were performed. The effects of parameters such as the structure of stiffening rib, the strength of LYP steel plate, the size of low-yield-point (LYP) steel plate, and the size of outer constrained steel plate were discussed. The results indicate that local buckling of steel tubular plates is likely to occur at the upper or lower end of those specimens, which belong to type II-A specimens with stiffened LYP steel tubular plates or type III-A specimens with T-shaped LYP steel plates, respectively. This led to the LYP steel plate cannot fully display its function. For type III-B and III-C specimens with embedded LYP steel plates and constrained steel plates on both sides, when the outer steel tubular plates buckle, the internally constrained LYP steel plates provide support for the outer steel tubular plates. The plastic deformation of the specimens is sufficient, and the deformation performance is good. For type IV-A specimens with LYP steel tubular plates and constrained steel plates on both sides, the mechanical behaviour of the new tubular steel piers is significantly improved, and increasing the height of the constrained LYP steel tubular plate can improve the compressive behaviour of the new tubular steel pier. Considering the effect of the steel plate thickness on bearing capacity and deformation performance, the thickness tw of the outer constrained steel plate should be equal to the thickness t of the common steel tubular plate, and the thickness tf of the LYP steel tubular plate should satisfy t ≤ tf ≤ 2t. Finally, a design formula is proposed to calculate the axial bearing capacity of newly designed tubular steel piers with constrained LYP steel plates. [ABSTRACT FROM AUTHOR]

Combined double thin-walled pier is a new kind of pier adopted in the urban transit system in China, whose longitudinal stiffness cannot be determined by adopting traditional methods. Aiming at this practical issue, this work proposed an alternative method for determining the longitudinal stiffness of the combined double thin-walled pier based on the train-track-bridge interaction. Primarily, the relationship between longitudinal stiffness of the pier and rail stress is underlined, based on which the proposed methodology is described in detail. Finally, a case study is conducted to validate the effectiveness of the proposed method. Results show that the train-track-bridge dynamic interaction theory is effective in determining the longitudinal stiffness of the newly designed and special pier. Rail stress and longitudinal displacement of pier top exceed their limit values with the change of pier longitudinal stiffness. The dynamic stress and thermal stress of rail are the two most important indicators in determining pier longitudinal stiffness, which should be paid attention to in practical engineering. [ABSTRACT FROM AUTHOR]

Pier settlement is unavoidable in the construction and operation of high-speed railways. This paper presents a work on the influence of pier settlement on additional structural stress of longitudinal connected track (LCT). First of all, the generation mechanism of additional structural stress of LCT caused by pier settlement is described in detail. On this basis, the deformation of LCT caused by pier settlement is analytically deduced and a dynamic model of high-speed train-LCT-bridge coupled system considering pier settlement is established based on the train-track-bridge dynamic interaction theory, adopting which the additional structural stresses of LCT are discussed from static and dynamic perspectives. Results show that pier settlement has a great influence on the stability of LCT. Additional tensile stresses of LCT appear at settlement pier location and two adjacent pier locations. Tensile stresses on top surface of slab and on bottom surface of base should be paid attention to. The behaviors of LCT at adjacent pier locations cannot be ignored in studying the influence of pier settlement on the system. To ensure the stability of LCT and running performance of train, the control value of pier settlement is suggested to be 10.5 mm from the static and dynamic perspectives in practical engineering. [ABSTRACT FROM AUTHOR]

In order to evaluate the uplift bearing capacity of belled piers beside slopes, a series of numerical simulations are carried out based on field tests data. First, a number of uplift loading tests of full-scale belled piers are carried out on the project site of transmission line in Anhui Province, China. Second, a slope-foundation model for numerical modeling is proposed and calibrated based on field tests data. The behavior of belled piers adjacent to slopes subject to uplift load is studied by numerical modeling. The impact of three parameters, including distance (a) from the belled pier to the crest of the slope, slope angle (β), and embedment depth (h) of the belled pier, has been investigated on the uplift capacity of the belled pier. Based on the simulation results, an attenuation coefficient (ω) is put forward for evaluating the reduction of uplift bearing capacity of the belled pier. The results show that the coefficient ω is negatively correlated with distance a and depth h, and the influence of distance a is greater than that of depth h according to the results of variance analysis, but the difference is not significant by F test. Moreover, the empirical equation between attenuation coefficient ω and three key factors a, β, and h had been presented by a series of fitting. [ABSTRACT FROM AUTHOR]

In this research study, horizontal impact tests were carried out on five reduced scale pier models using China's most advanced multifunctional ultrahigh heavy drop hammer impact test system and DHDAS dynamic signal acquisition and analysis system. Due to the fact that the traditional measurement method can only be used for local measurement damage, and the volatility is high, this paper proposes a test method for the modal frequency identification of the overall damage of reinforced concrete pier and applies the ultrasonic damage measurement method to verify the results. The tests analyzed the modal frequencies and ultrasonic velocity identifications for the purpose of evaluating the impact damages of bridge piers, as well as the relationship between them. The results showed that the modal frequencies were consistent with the ultrasonic waves in identifying and evaluating the damages to the piers. Also, the modal frequency damage factors were determined to be functions of the ultrasonic wave velocity damage factors. Therefore, the results of this study confirmed that it was feasible to characterize the impact damages of piers using a modal frequency method. [ABSTRACT FROM AUTHOR]

To study the seismic performance of hollow reinforced concrete piers under dynamic loads, nine hollow pier specimens with different stirrup ratios, reinforcement ratios, and axial compression ratios are designed and manufactured. The El Centro wave, Taft wave, and artificial Lanzhou wave are selected as seismic excitation for the shaking table test. The effects of the reinforcement ratio, stirrup ratio, and axial compression ratio on the failure mode, period, damping, acceleration and displacement response, dynamic magnification factor, ductility, and energy dissipation of specimens under different working conditions are studied. The results show that all the nine reinforced concrete piers have good seismic performance. Subjected to ground motion excitation, horizontal through cracks appeared on the pier surface. With the increase of ground motion excitation, the period of piers increases but the maximum period does not exceed 0.62 s, and the damping ratio increases as well and ranges from 0.02 to 0.064. With the increase of the ground motion excitation, the acceleration response of pier specimens increases, the dynamic magnification factor decreases, the displacement ductility coefficient decreases, and the energy dissipation of the specimens increases. The reinforcement ratio, stirrup ratio, and axial compression ratio have different effects on the above parameters. The test results can provide reference for seismic design of hollow rectangular piers and have certain engineering significance and value. [ABSTRACT FROM AUTHOR]

Currently, it is a challenge to effectively assess the seismic performance of the high-speed railway bridge line. To figure it out, this paper discussed the applicability of the Pushover analysis in the seismic fragility of the high-speed railway bridge. As the piers are the core components to resist the earthquakes, a typical high-speed railway bridge line consisting of 22 piers was established by the finite element software OpenSees. The influences of the different pier height and sites on the fragility analysis of the pies were investigated. From the component level, the seismic performance of the high-speed railway bridge line was evaluated by the Pushover analysis. The results show that the seismic responses of the piers by the Pushover analysis are agreeable with those by the incremental dynamical analysis when the peak ground acceleration is less than 0.4g. The high piers have better seismic performance than the lower piers. The high-speed railway bridge line exhibits good seismic performance under the 7-degree design earthquake (0.15g) and the 8-degree low-level earthquake (0.10g) but may be severely damaged under the 9-degree low-level earthquake (0.40g). [ABSTRACT FROM AUTHOR]

Uneven settlement widely occurs on the roadbed under urban viaducts in operation. Previous studies focused on the effect of soft soil foundation on the uneven settlement of roadbed, without considering the phenomenon and mechanism of uneven settlement at the junction of pier cap and the roadbed under viaduct. The interaction is now considered between the buried depth of cap, the relative stiffness between cap and road subgrade, and the uneven settlement of roadbed. Using the Midas GTS NX software, a numerical analysis model of the deformation of roadbed under viaduct is constructed to study the influence of viaduct cap foundation on the uneven settlement of roadbed under viaduct. The simulated results of uneven settlement of roadbed caused by urban viaduct pier cap show that (1) when the buried depth of cap exceeds 2.35 m, with the increase of buried depth, the fall of roadbed settlement tends to decrease, but the decreased amount is not significant. Considering the factors such as construction cost and complications of construction technology, it is suggested that the best buried depth of cap is about 2.5 m. (2) The fall of roadbed settlement decreases with the decrease of relative stiffness between cap and roadbed. When the relative stiffness exceeds 6.3, the decreasing trend of settlement fall is not significant. The concrete roadbed should have more stiffness in order to reduce the settlement. [ABSTRACT FROM AUTHOR]

Barge impact is a potential hazard for bridge piers located in navigation waterways. Protective structures of different types, for example, dolphin structures, artificial islands, and guiding structures, have been widely used in bridge designs against barge impact. However, such structures often imply high cost and suffer from difficulties in installation as well as maintenance challenges. This paper aims to devise and investigate a new type of crashworthy device which is comprised of vertically supported impact cap connected to the bridge pier using a series of steel beams in a frame-type arrangement. This sacrificial steel structure is designed to form plastic hinges for energy dissipation whilst limiting the force transmitted to the protected pier. The dynamic analysis of the proposed crashworthy device subjected to barge impact is conducted using a simplified impact model previously developed by the authors. The parametric studies in this paper show that the proposed device has a large energy dissipation capacity and that the magnitude of impact force transmitted to the bridge pier can be dramatically reduced. In addition, an optimization model is proposed in this paper to achieve the cost-optimized design of the crashworthy device for a given impact scenario with constraints as per the prescribed design requirements. [ABSTRACT FROM AUTHOR]

Summary: This paper introduces a new methodology for the automated processing of large point clouds for the diagnosis of structural pathologies in piers of masonry arch bridges. This method starts with the automatic segmentation of the global point cloud of the entire bridge in its different structural elements (piers, arches, spandrel walls, etc.). Later, piers were further segmented in order to be able to detect and quantify structural pathologies. Particularly, faults are based in geometric anomalies (tilts and skews) of the pier walls that might be indicators of stability problems of the entire bridge. The methodology was validated using several samples of representative masonry arch bridges. The obtained results demonstrate that this method can provide useful information about the structural health of the bridge requiring neither training in the technology nor advanced knowledge in the processing of laser scanning data. [ABSTRACT FROM AUTHOR]