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This study performed a bridge pier collar comparison for the purpose of reducing scour, while introducing a new collar design. The new collar, referred to as Collar Prototype Number 3, was designed based on an equilibrium scour hole and provides a method of controlling the horseshoe vortex. Numerical modelling was utilized to show the flow field and bed shear stress as a result of using Collar Prototype Number 3. A prototype model of Collar Prototype Number 3 and a flat plate collar were constructed for the purpose of comparing both experimentally under different flow conditions. Collar Prototype Number 3 proved to be an effective device as it reduced scour in terms of the maximum depth downstream of the pier and overall volume, in some instances, by up to 69.7% and 75.7%, respectively. Furthermore, Collar Prototype Number 3 outperformed the flat plate collar, especially because, unlike the flat plate collar, Collar Prototype Number 3 did not experience undermining.

Previous investigations have attributed some reinforced concrete (RC) bridge piers suffered significant damages during large earthquakes due to vertical ground motion effects. This has motivated this study to investigate the use of concrete-filled steel tube (CFST) columns as a more resilient and sustainable alternative to resist combined horizontal and vertical ground motions. The classic performance-based earthquake engineering (PBEE) framework is used to examine the seismic performance of a rigid-frame bridge with construction options of circular RC, circular CFST, and square CFST columns. The hysteretic response of each column is calibrated to the results of hybrid testing of columns under combined horizontal and vertical ground motions. The incremental dynamic analysis (IDA) is conducted using a suite of 50 near-fault records. The results are used to compare the observed damage states and quantify the repair sustainability metrics including repair cost (economic), repair downtime (social), and repair carbon emissions (environmental), as well as the loss of resilience. The losses are integrated with the hazard curves to compute the expected annual losses, all defined as a set of decision variables in the PBEE framework. The results confirm the outstanding seismic performance of CFST columns and highlight their benefits in improving the resilience and sustainability of critical and post-disaster bridges that are prone to strong multi-directional ground motions.

A superior seismic strengthening technology should be not only secure and reliable, but also economical and feasible for the widespread structures. In China, the gravity pier with low longitudinal steel ratio has been widely used in railway bridges, and most of them have insufficient seismic performance due to limited technological level in the early days. In this study, a novel preventive seismic strengthening technology with steel grid by planting and welding measures was presented for gravity railway bridge pier with flexural failure modes. Five 1/8-scale piers, including two different reference piers and three strengthening piers, were fabricated and tested through quasi-static test. It was shown that the piers exhibit uplifting and swaying behaviors due to highly-centralized crack at pier-footing region under lateral loading. The strengthening using steel gird led to a reduction up to 50% in residual displacement approximately, which was effective to prevent collapse of piers. The strengthening piers exhibited an enhanced the load-carrying capacity and cumulative dissipated energy by 120% to 150%, compared to the pier without strengthening. Moreover, the initial stiffness and cracking load of strengthening piers also were improved where the maximum increment was 1.5 times. The effect of strengthening thickness on strengthening efficiency was more significant than that of strengthening height. Therefore, it could be concluded that the seismic strengthening technology, by steel grid with reasonable arrangement at the pier bottom region, are suitable for gravity railway bridge pier with low longitudinal steel ratio in seismic zones.

According to recent data, many bridges tend to fail due to seismic inadequacy in design. Circular piers are more effective in reducing scour depth and increasing the durability of bridges than an elliptical bridge pier. The question is “whether circular pier performs better under seismic action than elliptical pier or not”. So a comparative study was conducted to analyze the behavior of circular and elliptical piers under earthquake forces, and complete nonlinear static pushover analysis was carried out for two different bridge models separately. Pushover curve data from Indian Standard Code was used to formulate the problem and performance outcomes of the bridges were analyzed. It was found that single circular pier showed no failure and better performance in both directions of the bridge, with more displacement capacity than double elliptical piers when subjected to incremental lateral loads. The design capacity (D/C) ratio in the longitudinal direction was 1.8 times more for single circular pier bridge and in the transverse direction, the ratio was 1.4 times more for double elliptical pier bridge for the considered earthquake situation. Results also showed 47% less drift value for single circular pier bridge compared to double elliptical pier bridge.

The catastrophic consequence of vehicle-pier collisions necessitates the research of vehicular impact forces on bridge piers. Since previous collision events that involve serious damage to bridge structures are mainly caused by heavy trucks, this study focuses on the impact force characteristic and mechanical behavior of trucks in collisions against piers. Using detailed finite element (FE) simulations, four typical trucks classified by Eurocode are selected to establish the truck-pier impact models. Then, more than two hundred impact cases are conducted to explore the influence of critical variables such as the truck type, impact velocity, and pier cross-section on the impact force and structural stiffness of the trucks. Based on the simulation results, the typical truck-pier impact process is identified, and empirical formulas for calculating the peak impact force (PIF) and equivalent static force (ESF) of piers imposed by the trucks are proposed. The importance of truck type on the truck-pier impact analysis is also highlighted. Besides, the impact force-crush depth relationships of the typical trucks are generated and simplified into a series of piecewise linear functions. For the anti-impact design of bridge piers, a simplified truck model is developed based on the mechanical behavior of the typical trucks and validated against simulation results obtained from detailed FE models.

From the field observations of bridge deck failures under extreme waves, it is shown many bridge decks were laterally displaced at varying displacements on the pier caps, and some decks with large lateral displacements even fell into the water. The repair cost varies with the lateral deck displacement, especially between different bridge states (Fixed state, Partially-displaced state, Falling-down state) after the disaster. To the author's knowledge, a comparative study of lateral displacements for T-deck and Box-deck under extreme waves has not been conducted. This paper discusses some fundamental questions related with the lateral deck displacement: (1) What are the influences of three essential parameters (relative clearance, wave height, deck weight) on the lateral displacements for two kinds of bridge decks? (2) Which kind of bridge deck is safer under the extreme solitary waves? In other words, is the lateral displacement of T-deck always larger or smaller than the Box-deck? (3) Does a larger horizontal or vertical wave force on two decks always induce a fiercer lateral motion response? (4) What is the most vulnerable condition for the failures of T-deck and Box-deck? Motivated by these questions, a comparative research on the wave-deck interactions for two movable decks under solitary waves is conducted by a numerical model solving the Navier-Stokes equations. A total of 330 numerical experiments based on this model have been designed to dynamically study the lateral responses of two bridge shapes under various conditions. This study provides researchers an insight into the dynamic properties for T-deck and Box-deck under solitary waves, and improves our understanding of the fragility of two decks under extreme waves.

In the present study, in view of the problem of nonlinear response caused by vehicle-RC pier collision, a new test system which can realize lateral impact is proposed, and two types of 1:3 scale RC components in five groups are subject to the lateral impact test at a velocity of 4.5 m/s. The system’s design characteristics represent the effect of stirrup spacing and axial compression ratio on the dynamic response of RC columns. In addition, the nonlinear response results of RC columns, such as impact force, acceleration, lateral displacement, failure mode and degree, are given in the test. Digital Image Correlation (DIC) technology is applied to the test. Next, the lateral strain response of RC columns during impact is measured, and the strain change process in every representative region is calculated. The data outlined in this study provide a reasonable basis for evaluating the shear capacity of RC columns and developing a finite element model (FEM). Finally, a typical FEM of vehicle-pier collision scenario is developed, while an improved equation for calculating the axial compression ratio-shear increment and a simplified calculation value of dynamic shear capacity of the RC pier are proposed.

Vehicle collision on reinforced concrete bridge pier (RCBP) frequently occurred all over the world in the past two decades, posing a potential threat to safety of the bridge. However, the impact-resistant design of RCBP in current regulations is only based on the equivalent static force of vehicle impact without considering the damage-performance correlation of the impacted RCBP. This study aims to establish the performance-based design procedure for the typical double-pier RC bridge against vehicle collision. By adopting the refined finite element models of light, medium and heavy trucks with the weight ranging from 3 to 50 t and impact velocity varying from 40 to 120 km/h, 54 numerical simulations of collision scenarios are carried out based on the validated numerical algorithm and material constitutive models. It derives that: (i) the dominated factor that evaluates whether RCBP fails or not under vehicle collision is the peak dynamic shear demand at the base of the RCBP, and related explicit expressions of the peak dynamic shear demand and capacity are further developed and verified; (ii) a new damage index, i.e., the ratio of peak dynamic shear demand to the dynamic shear capacity, is defined to evaluate different damage levels of the RCBP under vehicle collision; (iii) damage-performance correlation of the impacted RCBP is also established, e.g., the bridge is prone to collapse under vehicle collision once damage index exceeds 1.2. Finally, by proposing the impact-resistant performance objectives, the detailed performance-based design procedure is developed according to the importance level of roadway.

This paper aims to evaluate the seismic performance of isolated bridges under near-fault ground motions based on Energy Balance Method (EBM). This method invokes the concept of energy balance into the modal pushover analysis to assess the nonlinear behavior of lead rubber bearings on bridge piers. In EBM, the energy-based capacity curve is firstly obtained by the pushover analysis, while the demand curve is estimated based on the synthetic near-fault record. The target performance criterion can be derived by intersecting the capacity curve with the demand curve. The present paper also proposes the design method for seismic isolation based on the concept of EBM. The case study of an example isolated bridge at a near-fault site is used to illustrate the effectiveness and accuracy of the EBM. The results from this method are evaluated and compared with those from the nonlinear time-history analysis. Results show that the energy-based EBM is found to be able to evaluate the seismic performance of the pier isolated with lead rubber bearings under near-fault ground motions, which can be used as an effective alternative for rapid assess the seismic performance of isolated bridges The results also indicate that the EBM cannot only effectively evaluate the seismic responses of isolated bridges, but also can effectively estimation of the effect of isolation bearing in reducing the displacement and damage of piers.

Precast post-tensioned segmental (PPS) bridge piers mitigate global and local damages of bridge structures through natural hinges (joints between their segments) and rocking motion of their segments. The application of the PPS piers is currently growing in Accelerated Bridge Construction (ABC) where the segments are manufactured offsite with higher quality, and are assembled onsite in a short time. Structural vulnerability analysis of the PPS piers is very essential in extending their engineering implementation under seismic loading. Thus, this work particularly focuses on seismic vulnerability assessment of the PPS piers. To achieve this goal, a previously developed and experimentally validated robust Finite Element model of the PPS piers in OpenSees programme is used to analyse PPS piers of various aspect ratios. An equivalent reinforced concrete (RC) pier to one of the PPS piers is also analysed. Incremental Dynamic Analysis (IDA) is performed and fragility curves are generated to evaluate seismic performance of the PPS piers and an equivalent RC pier using a suite of 44 far-fault ground motions. The IDA results show that slenderising the PPS pier tends to change the failure criterion from the yielding of the post-tensioning tendon to the strength loss of the pier. For squat and slender piers, the yielding of the tendon governs the failure of the pier while the strength of very slender PPS piers drops due to second-order effects at small drift values prior to the yielding of the post-tensioning tendon. It is also found from fragility curves that squat piers are more prone to seismic collapse compared to slender piers. The equivalent RC pier reaches slight and medium damage states in lower intensity measures compared to the PPS pier.

In the maritime environment, the persistent attack of chloride ions will induce degradations of structural performance. Because of the surrounding exposure conditions, coastal bridge piers usually undergo discrepant deteriorations along the height, causing the maximum damaged position (MDP) to transfer from the conventional pier bottom to the zone that corroded most seriously. This study presents an analytical method to forecast the transfer time of the MDP for coastal bridge piers. The relationship between the structural capacity and seismic demand of the bottom section in each zone is monitored synchronously, aiming to capture the time and place that the structural capacity is first exceeded by the seismic demand. Next, an illustrative example of coastal bridge piers is adopted to demonstrate the proposed approach. The time-dependent lateral deformation capacity of the coastal bridge pier is investigated by considering the effect of the transfer time of the MDP. The analytical results show that the ultimate drift ratio of coastal bridge piers increases firstly and then, decreases significantly when the discrepant corrosion damages along the pier height is considered. As for the conventional simplified corrosion mode, i.e., using an equivalent mean corrosion level to describe the corrosion level for the global bridge pier, it cannot be adopted to estimate the actual time-dependent seismic performance of coastal bridge piers corroded non-uniformly along the height.

Near-fault vertical ground motions (VGMs) caused great damage to bridge structures, but investigations of the effect on probabilistic seismic performance and structural vulnerability are insufficient. For this purpose, a novel model of bridge seismic fragility surface conditioned on the horizontal peak ground velocity (Vx) and the αVH (ratio of vertical to horizontal ground motion) is proposed. The quantitative formulation for probabilistic seismic demand model (PSDM) and probabilistic seismic capacity model (PSCM) of bridge piers considering the effect of VGM are established, and then the empirical model of fragility surface with the parameters of Vx and αVH is obtained by convolution. A simply supported bridge model is simulated in OpenSees as an illustrated example to establish the seismic fragility surface under the combined actions of horizontal ground motion and VGM. Furthermore, the damage probability (Fr) influenced by VGM is analyzed compared with the damage probability (Fr0) without VGM, and the sensitivity intervals of the difference between Fr and Fr0 for varying damage states are identified. The mechanism of fragility variation under VGM is explored, indicating that the variation of seismic demand caused by VGM is the main reason. Finally, the seismic fragility surface model considering VGM is applied to a set of variable piers, and the sensitivity interval associated with the fundamental period is investigated under different Vx.

Coastal bridges exposed to the marine environment always suffer from non-uniform corrosion along the pier height. As the non-uniform corrosion increase, the material properties of the pier in the splash and tidal zone deteriorates significantly, affecting the seismic performance of the pier. In this study, four scaled bridge pier specimens were designed and fabricated. These specimens were subjected to different level of electrical accelerated corrosion in the proposed splash and tidal zone. Then, the cyclic load tests were conducted on the four bridge pier specimens. The hysteretic behavior, loading capacity, ductility, energy dissipation capacity and mean curvature of each specimen were analyzed. It was found that with increasing corrosion level, the load capacity, ductility and cumulative energy consumption of the specimens decreased. When the corrosion was severe enough, the location of the plastic hinge will transfer from the pier bottom to the corroded zone.

Concrete bridge piers are vulnerable to strong ground motions because of inducing significant residual drifts, which reduce the seismic resilience of bridges. A broad range of mitigation techniques is presented in the literature to reduce the vulnerability of bridge piers located in high seismic zones. Hybrid reinforced concrete piers are the most popular techniques to improve the seismic resilience of highway bridges. In addition, posttensioned segmental bridge piers are proposed as an alternative to expedite the construction procedure and also meliorate the performance of bridges in terms of residual deformations. However, very limited studies investigated the seismic performance of a whole bridge, especially for the purpose of comparing seismic resilience of the bridge columns. In this paper, a comparative study is implemented to explore the seismic vulnerability of a bridge reinforced with a hybrid configuration (i.e. combination of shape memory alloys (SMA) and normal-strength bars, and combination of high-strength and normal-strength bars) as compared to a reference conventional pier, which fully reinforced by normal-strength rebars. Moreover, a posttensioned segmental pier is considered to evaluate the strength and self-centering ability of this pier as compared to the monolithic ones. To do so, a 2D bridge model is developed in OpenSees simulation platform. Fragility curves are developed to assess the seismic vulnerability of the bridge model constructed with different piers. In this regard, a suite of 20 near-fault earthquake motions are applied to the bridge through Incremental Dynamic Analysis (IDA). Each of these records is scaled to 15 Peak Ground Accelerations (PGAs) ranging from 0.1 g to 1.5 g . The fragility curves reveal the chance of failure for each bridge model and aid in determining the impact of each pier on the seismic vulnerability of the bridge.

This article presents a study to evaluate the structural response of a cable-stayed bridge under a novel system, partially earth-anchored system with crossing cables at the main span. Six side-to-main span ratios, ranging from 0.24 to 0.39 in increments of 0.03, are tested for different bridge response parameters for both the superstructure and substructure. The loads considered in the analysis are the dead load and traffic load. Three-dimensional finite element models of the bridge are developed using structural analysis software SAP2000 and are validated based on the data available in the literature. From this study, it is found that the side-to-main span ratios have a significant effect on girder axial force and anchorage forces while having a very minor effect on cable axial forces. The results also show that the ratio does not affect the bending moment of the main span, but that when a small ratio is considered particular attention needs to be paid to the pier farther from the pylon to avoid uplifting. Deck vibration and longitudinal movement, as well as pylon longitudinal displacement, are not to be an issue for this super-long bridge.

The seismic performance and design method of fabricated concrete bridge piers limit their applications in complex and harsh environments. In this study, a continuous bridge pier in an 8-degree seismic fortification intensity area was considered as a prototype. Two 1/3-scale models were designed and manufactured. The specimens were connected via a grouted sleeve connections (SFP) and a grouted sleeve prestressing tendon composite connections (SSFP), respectively. Moreover, a cast-in-place 1/3-scale model (reinforcement concrete pier, RCP) was designed as a comparison specimen. Quasi-static experiments were performed on these three specimens. The seismic performance of the specimens was analysed according to the failure phenomena, bearing capacity, displacement ductility, stiffness, energy-dissipation capacity, and residual deformation. On these basis, a bearing-capacity estimation method for SFP (including SSFP) was developed and validated. The results indicated that the damage to the SFP and SSFP mainly accumulated along the top and bottom of the sleeves. The plastic hinge area of the SFP and SSFP moved up or down. Thus, the damage to the SFP and SSFP was concentrated at the joints. Cracks first occurred at the seam of the two fabricated specimens when the loading drift was relatively small. Then, the concrete at the loading edge of the joints was crushed. Furthermore, the longitudinal bars yielded and broke. Finally, the specimens failed. Compared with the RCP, the SFP and the SSFP had larger yield and ultimate displacements. The bearing capacities of the RCP and the SFP were similar. However, the bearing capacity of the SSFP was significantly higher. The bearing capacities of the SFP and SSFP did not decrease significantly before the specimens failed. Compared with the RCP, the SFP had a lower initial stiffness, a lower stiffness degradation rate, similar displacement ductility, smaller residual displacement, and less cumulative energy dissipation. The SSFP was better than the SFP with regard to the displacement ductility, initial stiffness, and cumulative energy dissipation. Thus, the SFP and SSFP can satisfy the seismic requirements of high-intensity areas. The proposed bearing-capacity estimation method can be used for the seismic design and evaluation of SFPs and SSFPs.

Resilience in bridges is of paramount importance as bridges are important transport assets that maintain mobility after disasters. The most common cause of extreme stress development on structures and especially bridges is dynamic loads due to floods, earthquakes, strong winds, truck and ship collisions. In the international literature, there an ongoing research in support of adaptable and low-damage bridge connections for bridges and structures exposed to dynamic loads. This paper focuses on the design and assessment of a novel connection based on extensive numerical modelling of a 3D Finite Element (FE) model of the connections developed in Abaqus. The connection, which is essentially a resilient hinge, connects the foundation with the bridge pier and the latter with the deck, which are the positions where typically RC hinges are formed during extreme dynamic loads, e.g. earthquakes. A similar connection was designed before, however, this paper offers a design methodology and advances the connection by providing improvements to its mechanical characteristics, i.e. the geometry, resolving issues with regard to stress concentration by improving the contact surface geometry, the consideration of the friction and the optimization of its components. The paper concludes with a discussion on the connection constructability, therefore enabling further applications of the proposed design. The results also demonstrate that even though the rebars of the hinge undergo excessive elongation, the connection maintains a significant bending moment capacity, therefore not hindering the integrity of the bridge. Moreover, it is observed that the compressive zone of the hinge remains intact, thanks to the high strength of the steel, therefore no shortening of the RC column is expected.

Vehicular collision with bridge pier can cause significant structural damage, and even partial or full collapse of the bridge, while the existing work mainly focuses on the vehicular-impact resistance of bridge pier. This study aims to study the collapse process and damage levels of the bridge collided by medium and heavy trucks. Firstly, the refined finite element (FE) model of the typical simply supported two-span double-pier RC bridge is established via the commercial software LS-DYNA, and the adopted material constitutive models and numerical algorithms are validated by comparing with the prototype truck-pier collision test and full-scale drop-weight test on RC beam. Then, the validated FE model is employed to numerically reproduce the actual heavy truck collision accident involving the collapse of bridge, and the dynamic behaviors and collapse process of the collided bridge are analyzed. It shows that, for the present bridge type: (i) truck-bridge collision is not a single impact but a successive impact with bumper, engine and cargo, in which the shear failure on the reinforced concrete bridge pier (RCBP) induced by the engine impact is the dominant factor resulting in the bridge collapse; (ii) during the collision process, the impacted RCBP firstly suffers shear failure at the bottom, and followed by the inclination of the bent cap and superstructure, and then the neighboring RCBP sustains flexible-shear failure at the top, which eventually results in the instability of substructure and collapse of superstructure. Furthermore, a total of 35 truck-bridge collision cases are numerically simulated and assessed, and a new quantitative damage evaluation approach, including the modified damage index, damage level and evaluation criterion, is proposed for the bridge under vehicular collision. In addition, the relationship between the damage level of the collided bridge and superstructure inclination is clarified, which is beneficial for bridge engineers to feasibly assess the vehicular-impact resistance of bridge.

During earthquakes, large relative displacements can be generated between different structural parts of a bridge. This can lead to collisions between the girder ends and the abutments and can even result in the girder unseating. A widely used prevention method adopts unseating prevention systems. The commonly cable-type unseating prevention device (C-CUPD) has low energy dissipation capacity and its cable fractures easily during strong earthquakes. In order to address these shortcomings, an energy dissipation cable-type unseating prevention device (E-CUPD) with an energy absorption tube is proposed in this study. The paper describes the basic structure and working mechanism of the device, and then investigates its energy absorption characteristics and limit performance, drawing upon theoretical analysis, numerical simulations, and testing of a scaled model. The influence of structural parameters and loading velocity on the energy absorption characteristics of the device are discussed, and the seismic responses of the bridge equipped with the device under different seismic input intensities are studied. The results show that the longer the device, the thicker the tube, and the larger the diameter, the better the energy absorption performance, while the larger the outer diameter, the lower the energy absorption performance. The axial expansion load of the energy absorption tube increases with an increase in the impact velocity. Before and after the characteristic velocity of 1 m/s, the sensitivity of load to velocity is weakened and the variation range decreases gradually. The integrity of the bridge structure equipped with the E-CUPD is improved and the seismic force is evenly distributed among piers with an acceptable value of spring displacement. The device can effectively reduce the relative displacement of the piers and beam subjected to different earthquakes and can absorb a large amount of seismic energy. With the increase in the seismic input intensity, the limiting effect of the E-CUPD becomes more prominent. At the higher seismic input intensities, the relative displacement of the pier and the beam can be reduced by nearly 30% compared to bridge without device. Compared to the C-CUPD, the E-CUPD can improve the limiting performance by about 15%.

Ground seasonal freezing and thawing in cold regions can alter boundary conditions of bridge pile foundations and influence their seismic behaviors. This article describes a test apparatus with a custom-designed cooling system for investigating the seismic behavior of pile foundations in seasonally frozen ground. Two 1/8-scale models of a reinforced concrete bridge pier with pile foundations were fabricated for conducting quasi-static tests under unfrozen and frozen conditions. Test observations and data were used to analyze failure characteristics of pile foundation subjected to cyclic lateral loading under the two conditions and reveal the frozen soil effects. It was found that ground freezing greatly enhanced the loading carrying capacity while partly weakened the deformation capacity of the pile-soil system. It is not easy to fail if upper layer soil was frozen, and the frozen soil layer shifted the pile failure zone upward compared with the unfrozen condition. The strength degradation was obvious in the pile-soil system under frozen condition due to the fracture of the steel bar. Furthermore, the pile foundation in frozen soils exhibited more stable and reliable energy dissipation than the pile foundation in unfrozen soils under large seismic load, which was attributed to the severe damage of the pile foundation in frozen soils. A simplified force–displacement model was proposed for the pile-soil system under unfrozen and frozen conditions based on the testing results. These results can provide references for seismic design of reinforced concrete pile foundations in cold regions.

In this study, three-dimensional numerical analyses were carried out to investigate the effects of reinforcement pullout resistance including facing connection strength on the behavior of geosynthetic-reinforced soil (GRS) piers under a service load condition. Three different piers were investigated in this study, which simulated different levels of reinforcement pullout resistance. Each pier had two cases with different reinforcement stiffness J and reinforcement spacing Sv but the same ratio of J/Sv. Numerical results showed that reinforcement pullout resistance had a significant effect on the behavior of GRS piers. When the pullout mode prevailed, the case with small Sv and low J had smaller lateral facing displacements and vertical strain of the pier under the same applied pressure as compared to the case with large Sv and high J when the ratio of J/Sv was kept constant. When the pullout mode did not prevail, two cases with the same ratio of J/Sv showed similar performance despite different combinations of Sv and J were used. To more effectively mobilize reinforcement strength and improve GRS pier performance, small reinforcement spacing or high-strength facing connection should be considered when sufficient reinforcement pullout resistance cannot be guaranteed otherwise.

The seismic performance of a steel tubular bridge pier in a five-span continuous girder bridge system was evaluated through dynamic non-linear time-history analysis under strong ground motions. The seismic performance of the hollow steel tubular (HST) and partially concrete-filled steel tubular (PCFST) bridge piers was assessed with different eccentricities of superstructure. Considering the variation of ground classification under rare earthquakes, six seismic waves were input. The analytical results indicate that the eccentricity of superstructure has little effect on the maximum displacement response of the HST bridge piers and the PCFST bridge piers under ground motion excitations in the longitudinal (LG) direction; however, under the ground motion excitations in the transverse (TR) direction, the maximum displacement response of the bridge piers increases when the eccentricity (e/H) increases from 0 to 0.2, which implies that eccentricity affects the seismic response of the two types of piers. Both in the LG direction and TR direction, the HST piers have reached their yield strengths; stress concentration and local buckling were observed around the plastic hinge zone and the load bearing capacity decreases. Although the PCFST piers entered the elasto-plastic range, the expansion of local buckling deformation of the steel tubular column has been restrained by the concrete in-fill. According to the simulated results, the PCFST pier exhibits high ductility and bearing capacity, which can improve the seismic performance of the bridge system.

Observations from recent earthquakes around the world have revealed the destructive nature of near-fault ground motions that cause significant damage to structures. On the other hand, the effect of long-duration motions on seismic demands has attracted a lot of interest over the last decade. This study aims to numerically explore how long-duration (LD) motions and near-fault (NF) ground motions affect the seismic performance of a seismically designed bridge pier and compare the response with short duration far-field (FF) motions. A fiber based nonlinear finite element model of a bridge pier is used for evaluating the damage potential of different types of ground motions. The bridge is assumed to be a major route bridge located in Western Canada and is designed following the performance-based seismic design requirements of the Canadian Highway Bridge Design Code. A set of 20 long-duration motions, 20 spectrally equivalent near-fault and far-field motions are used to study the effect of ground motions on drift and damage measures of the bridge pier. The results indicate that since the current design guidelines consider neither the ground motion duration effect nor the pulse effect of near-fault motions, damage measures for performance-based design should be reviewed to take into account the duration effect as well as the velocity pulse associated with NF motions.

This study presents simplified analytical model to analyze the seismic response of typical bridge considering soil–pile structure interaction (SPSI). For this purpose, a typical bridge was selected as a case study. A 6 DOF model was developed by considering the effects of SPSI. In order to evaluate the performance of the analytical model, modal analysis of MRO bridge was first performed. According to the results, the natural period of the MRO bridge was 0.40 s. The natural period calculated in this study differs by 1.7% to 16% from other studies. Three earthquake records were then used to examine the performance of the proposed analytical model for predicting the seismic behavior of the bridge. The analytical model can predict the response of the maximum acceleration of deck up to 16% difference from that of the instrumented structure. Considering the effects of SPSI, the calculated acceleration response for bridge deck is on average 5% to 40% closer to the instrumentation data than the fixed base condition. The proposed analytical model could predict the acceleration response spectra for all three earthquakes with a relatively good approximation. Considering the effects of soil–pile structure interaction, the calculated natural period of bridge system is 10% to 40% closer to the instrumentation data than the fixed base condition.

In the experimental assessment of the in-plane behaviour of unreinforced masonry (URM) walls containing openings, accurate measurement of the deformations occurring in the pier and spandrel substructures is important. Eight full-scale perforated URM walls were tested under in-plane cyclic loading and constant vertical pre-compression load. To measure the deformation of the walls (pier-spandrel substructures) during testing and to capture the full-field cracking of the masonry, a two dimensional (2D) Digital Image Correlation (DIC) technique was used in parallel with traditional hard-wired instrumentation (Linear Variable Differential Transformers, commonly referred to as LVDTs for short). This paper describes the detailed procedures of using DIC in large scale masonry wall testing. Firstly, the digital images at the first peak of each displacement amplitude in both push and pull directions for one specimen were analysed using the VIC-2D software to validate the DIC results against the LVDT recorded measurements. After confirming the accuracy of the DIC measurements for the specimen, the pier-spandrel movements and the cracking analyses of all the walls were performed in order to better understand the integrity of these elements during cyclic in-plane loading.

Use of high-strength steel bars (HSSB) in RC bridge piers reduces the amount of reinforcement or enhances bearing capacity of RC piers. However, the use of HSSB could come with reduction in the energy dissipation of RC member, which used to be considered detrimental to the seismic performance of RC bridge piers. This paper revaluates the effects of HSSB on seismic performance of RC piers by comparing that with normal steel bars (NSB) through fragility analysis. Maximum drift ratio (MDR) and maximum section curvature (φm) are considered as engineering demand parameters (EDPs) to represent the deformation demands and section damage of RC piers, respectively. A fiber-based finite element model (FEM), calibrated by a set of shaking table tests of RC portal frames reinforced with NSB and HSSB, is adopted to simulate the nonlinear dynamic response of RC piers. Fragility curves using probabilistic seismic demand model (PSDM) are developed to compare the relative vulnerability of RC bridge piers reinforced with steel of different yield strengths. The analysis results indicate that, when using HSSB to replace NSB by equal volume replacement, the RC piers have similar deformation demands (MDR) but significantly less section damage. On the other hand, when using HSSB to replace NSB by equal strength replacement, the deformation demands (MDR) of RC piers slightly increase (about 5%) due to the decrease of post-cracking stiffness under small reinforcement ratio. In spite of slight increase of deformation demands, the use of HSSB by equal strength replacement still reduces RC piers’ section damage since the use of HSSB enhances the elastic deformation and then reduces the plastic deformation of RC piers. Moreover, as elastic deformation accounts for a higher proportion of total deformation for taller piers, the reduction amplitudes of section damage are more evident when using HSSB in taller piers. On the whole, the application of HSSB to replace NSB is more likely to be beneficial to the seismic performance of RC piers.

In order to evaluate the effect of seismic isolation on random seismic response characteristics of a track-bridge system, in this paper, a three-dimensional detailed nonlinear dynamic model consists of rail, CRTS II slab ballastless track, high-speed railway simple supported bridges, isolated bearings, piers, pile foundations from top to bottom, is established by OpenSEES. The stochastic process of ground motion constructed by the random harmonic function is taking as random excitation, and the probability density evolution method (PDEM) is applied to investigate and analyze the system from the random perspective. On this basis, the influence of FPB bearing and the different FPB parameters (such as equivalent radius) on the random seismic response of the track-bridge system is studied. Thereby, aplenty probabilistic information (probability density evolution function, mean value and standard deviation) can be gained of seismic response of isolated bridges with different isolation parameters and non-isolated bridges of the high-speed railway track-bridge system under the excitation of random earthquakes by case study. Through the comparison of random seismic responses of non-isolated bridge and isolated bridges with different parameters under random ground motions, the favorable and unfavorable effects of seismic isolation for high-speed railway bridges are explored and demonstrated from a random point of view. The comparison of the random seismic response under different cases are discussed and significant outcomes are drawn. Results show that: The use of isolation bearing can reduce the response of track structure and pier, but meanwhile, increase the response of bearings. The change of the equivalent radius of the isolation bearing has no obvious influence on the random response of the pier and the track structure, but will to some extent bring the change of the bearing response. The results can be used for the seismic design and maintenance of the railway high-speed bridge.

In recent years, aluminum alloy bridges have been constructed in China, but a lack of aluminum alloy design and construction standards limits their further development. Traditional concrete and steel design theory cannot be completely adopted for aluminum alloy in large bearing structures. To introduce the structural design of a two-span continuous aluminum alloy truss arch bridge, this paper describes the material type, section design, component connections and bridge bearings in detail. Deflection and stress under live load are analyzed by means of a finite-element model to prove that the allowable deformation can be much greater than L/800 due to low stress in the members. Additional flexural stress subject to large eccentricity cannot be neglected, and the allowable joint eccentricity is proposed as 5% of the section height of the upper or lower chord, or about 15.0 mm. As a result of large ratio of live load to dead load, aluminum alloy footbridges reveal a rapid drop in frequency and pedestrian comfort when pedestrian mass is considered in the vibration analysis. Aluminum alloy footbridges are more sensitive to pedestrian mass than steel footbridges, and the comfort evaluation considering pedestrian mass is very necessary in design. Elastic buckling results reveal that steel and aluminum alloy footbridges have similar buckling modes, while aluminum alloy footbridges have lower buckling eigenvalue and ultimate bearing capacity. Furthermore, nonlinear buckling analysis of bridges is used to identify vulnerable members and improve structural stability by strengthening the local members. As a result, four rows of additional diagonal members near the middle pier were installed, and the elastic and nonlinear buckling bearing capacities reached 2.67 and 2.89 times the design pedestrian load, respectively. The additional diagonal web members were proved to play a significant role in increasing structural stability and evenly distributing the pedestrian load.

The purpose of this paper is to investigate the influence of typical parameters on seismic fragility curves of reinforced concrete (RC) piers of continuous steel box girder bridges. Typical parameters considered include the pier heights, pier section types, and total length of bridges. Twenty recorded ground motions from historic seismic events are randomly selected for fragility analyses. The finite element analysis program, OpenSees, is employed to perform nonlinear dynamic analyses of the bridges. A set of damage states of bridge piers is proposed based on the damage index, which is based on the drift ratio of the pier. Fragility curves of piers are eventually generated using maximum likelihood estimation. The numerical analysis results show that the bridges with shorter piers are less vulnerable to earthquakes than those with higher piers. Moreover, the wall pier types have significantly improved seismic performance compared with the other types. The fragility analysis results also reveal that the total bridge length has notably affected to seismic response of bridges.

A continuous bridge, horizontally curved in plan and isolated with Lead Rubber Bearing (LRB), has been investigated under seismic loading conditions. Two recorded ground motions, representative of historical earthquakes along with far-field (Imperial Valley) and forward directivity effect (Turkey), respectively, have been considered. The bi-directional effect of the bearings considering interaction behavior of bearing and pier has been determined. Modeling and analysis of the bridge have been done by finite element approach. It has been noticed that there is a significant influence of bi-directional loading and the same is found to be maximum in Turkey ground motion which might be due to forward directivity effect.

The behaviour of bridge piers supported on shallow foundations under static and cyclic rotations has been studied through several laboratory tests. A brief review on the observations made by several researchers on the responses of bridge piers on shallow foundation is presented in this paper. During an earthquake, the bridge elements are subjected to horizontal, vertical and rotational movements. In bridge analyses, simulation of bridge elements is done by simple models containing several springs and dashpots, wherein the springs are simulated by corresponding spring constants. Recently, the evolution of performance-based approaches in the design of bridge structures has lead to the incorporation of force–displacement (P-Δ) relationships in bridge design guidelines. The (P-Δ) relationships represent the response of bridge elements under translation movement. The rotational behaviour of bridge elements can be represented by Moment – rotation (M-θ) relationships. The M–θ relationships of bridge piers under rotation have been developed and studied by several researchers. In this paper, a detailed review of several shake table and centrifuge studies conducted to understand and analyse the behaviour of bridge piers supported on shallow foundations has been done in order to identify the various factors controlling the behaviour of shallow footings under static and cyclic rotations.

In the present study, seismic design of a bridge curved in plan has been done for various response reduction factors (R) and the performance has been investigated as per FEMA-356 performance based criteria. Both uni-directional and bi-directional nonlinear dynamic time history analyses have been performed for the bridge. The performance of the bridge in terms of pier ductility demand has been determined for Kobe earthquake ground motion, compatible for Design Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE) response spectrums. For different values of R-factors, suitable value of safe pier diameter of the bridge has been determined. The strength reduction factor and over strength factor have also been determined for various cases considered. It has been obtained that the bi-directional effect increases the performance state and ductility demand of the bridge. The maximum R-factor of 2.5 can be recommended for the studied bridge.

The proportion of motor vehicle crash deaths involving a collision with fixed objects is not decreasing. To address this issue and consequently to decrease transportation hazards, a novel crash cushion comprised of load-bearing blocks was introduced. Its alpha version is easily and inexpensively obtainable; the beta version is suitable for use in harsh environments. In this contribution, the effect of the collision on imaginary vehicle passengers is examined. Besides, the effect of impact velocity on collision severity is discussed and both versions of crash cushions are compared in occupant injury potential. The effect of a combination of crash cushions with different crashworthiness measures is also studied. Inferences drawn from this study can be used by designers and contractors to assess the collision severity and optimize the use of the cushioning elements. The presented cushioning elements can replace stones and solid blocks in cross-drainage culverts, but hypothetically they could also be used in other structures which pose risks around traffic lanes or in underwater protection of bridge piers.

Reinforced concrete (RC) bridges exposed to marine environments significantly suffer from steel bar corrosion. Steel bar corrosion is responsible for strength deterioration of steel and concrete material, damage in steel-concrete bond, spalling of cover concrete, and so on. This study presents a numerical model that can simulate the structural behavior of corroded RC bridge piers under seismic action. In the numerical model, corrosion-induced damage modelled through different constitutive laws for corrosion-induced cracking, concrete and steel properties, and bond between steel and concrete. The numerical model for RC bridge piers is validated using the experimental studies available in the literature. The structural behavior obtained in the numerical analysis, i.e., lateral load resistance capacity, cracking length and crack patterns are in good agreement with the experimental study. The analysis results demonstrated that rebar corrosion significantly deteriorates the structural performance (i.e., load resistance capacity, displacement capacity, etc.) of corroded RC bridge piers. The findings of this study will be useful in assessing the residual structural performance of the RC columns with rebar corrosion.

Elastomer bearings are design efficient and economical, so these are more widely used for bridge construction. Steel bearings were predominantly used before and their performance was good with few disadvantages due to their corrosive nature and high maintenance. Hence elastomer was introduced as a matrix material for steel bearings. In present study, analysis of mechanical properties is carried by changing elastomer material. The results showed that it is better to produce strong and effective reinforced elastomer bearing using material other than natural rubber. The study compares results of bearing elastomer using silicone rubber, PTFE (Polytetrafluoroethylene) with the conventional synthetic natural rubber elastomer bearing. The effect of shape on maximum stress and deformation is also analysed. The bearing used in the case study is designed for forces applicable to metro rail viaduct. The load calculations are done using the specification provided by BMRCL (Bangalore Metro Rail Corporation Limited). The analysis for stress and deformation is performed using ANSYS. The maximum stress, strain and deformation in bearing using new materials as elastomer were found to be lesser than the bearing using neoprene elastomer bearing.

Friction pendulum bearing (FPB) is a sliding-based isolator, widely used in the seismic design of the bridge structure. However, there is neither unified standard nor complete evaluation system to evaluate the specific isolation effectiveness of FPB-isolated bridges with different pier heights. In this paper, the prototype bridge finite element models (FEM) of the typical simply supported girder bridges on the double-track railway in China, are established and studied. These bridge FEM differ in the pier height range of 4–60 m. Each FEM adopts two types of bearing: FPB (isolated bearing) and spherical steel bearing (non-isolated bearing). The nonlinear time history analysis is carried out to compare the seismic responses of FPB-isolated and non-isolated bridges. Based on the comparison results, the seismic isolation ratios of FPB are defined and obtained. In addition, a new criterion index is presented to quantifiably measure the effectiveness of the seismic isolation of FPB-isolated bridges with different pier heights, which is beneficial to the further popularization and application of FPB in the seismic design of bridge engineering.

The benefit of fiber reinforced concrete (FRC) to the seismic performance of bridges under different earthquake scenarios and damage mechanisms has not been fully addressed. This paper focuses on evaluating the seismic performance of bridge piers considering both flexural and brittle failure mechanisms at different damage states under both far-field and near-fault ground motions by fragility functions. To achieve this goal, 30 near-fault and 30 far-field ground motions were selected for nonlinear time history analysis. Both Cloud Analysis and Incremental Dynamic Analysis (IDA) were employed to establish the relationship between the Engineering Demand Parameter (EDP) and Intensity Measure (IM) for developing the fragility curves of piers. Cloud Analysis was compared by IDA to verify whether it is reliable when using deformation-based and force-based EDPs. Fragility curves were developed for FRC piers reinforced with different fiber types to study the effectiveness of fiber types to improve the seismic performance of bridge piers. The results concluded that the near-fault records increase the seismic demands by about 5% for FRC piers and 10% for RC piers compared to far-field earthquakes. The bridge piers reinforced with polypropylene fibers possess less vulnerability for both flexural and brittle failure mechanisms at different damage states than those reinforced with steel fibers. In addition, Cloud Analysis can provide reliable fragility estimates of bridge piers when using both force-based and deformation-based EDPs.

This study uses the time-dependent fragility analysis method, based on the Duracrete model and previous experimental results, to determine the probability distribution types and statistical characteristics of various environmental parameters and corrosion parameters. In this paper, an analysis framework is proposed to study the seismic fragility of bridges under the action of chloride ion corrosion and scour. With the increase of scour depth, the seismic fragility of the bridge in the example shows nonlinear growth, and the fragility of the laminated rubber bearing is higher than that of the pier, which makes the laminated rubber bearing sustain more significant damage than the pier when the earthquake occurs, thus playing the role of a “fuse” and reducing the seismic damage of the pier. Based on the Duracrete model, the degradation law of reinforced concrete performance with time was obtained by the Monte Carlo method under a chloride ion corrosion environment. Compared with the apparent increase of bridge pier fragility, the fragility change of the laminated rubber bearing was not noticeable and showed a trend of increasing first and then decreasing. Under the combined action of chloride ion corrosion and scour, the seismic fragility of the laminated rubber bearing in the early service stage of the bridge is dramatically higher than that of the pier, which leads to the laminated rubber bearing being damaged before the pier to protect the pier in the case of an earthquake. With the increase of service time, the seismic fragility of the pier is gradually higher than that of the laminated rubber bearing, which becomes a weak link in the anti-seismic system of bridges.

In order to study the effect of the vertical deformation of continuous beam structure of CRTS Ι slab ballastless track on rail deformation, this paper analyzes the mapping mechanism of the structural vertical deformation-rail deformation. Based on the principle of stationary potential energy, the work derives an analytical expression for a mapping between the vertical deformation of continuous beam structure and rail deformation by considering the effect of the subgrade. Then, the mapping relation between the vertical deformation of various typical bridge structures and rail deformation was calculated using analytical method. The results were compared with those obtained using ANSYS finite element method. The effects of four factors on rail deformation were investigated, namely, pier settlement, staggered steps on girder, rotation angles on beam ends, and number of spans of simply supported beam. The calculation results obtained via analytical method and those obtained using finite element method fit well with each other, verifying the rationality and correctness of the analytical method. The expression for analytical method is concise and can easily obtain the mapping relation between the structural vertical deformation and rail deformation using the displacement boundary conditions. The vertical deformation of the rail was proportional to the vertical deformation of same typical structure. Both inside and outside the rail deformation area, the length of rail deformation section did not change with structural vertical deformation. When there were simply supported beams at both ends of the continuous beam, the number of spans of simply supported beams had no significant effect on the rail deformation caused by the vertical deformation of typical continuous beam structures. When there were no simply supported beams, the settlement of side pier of continuous beam caused rail deformation similar to the staggered step of girder.

The spatially curved urban flyover may deliver different seismic response with the straight plain bridge owing to its unsymmetrical structures. This paper carried out a seismic fragility analysis on a representative spatially curved flyover, composed of one curved segment and two straight segments. Twenty-two ground motions at five intensities and 18 attacking angles were considered in the analysis, in a total of 1980 analyzed cases. The collapsed realizations were accounted and discussed firstly. Then, the probabilistic seismic demand model of the peak compressive and tensile strains was developed for each pier under eight attacking angels. The strain-based damage states were proposed. Then the damage probabilities of the piers were derived According to the distribution of the damage probabilities, the short piers in the spatially curved bridge are easy to sustain minor damage but no major damage. The minor damage probability didn’t present visible attacking angle dependency, but major damage probability did exhibit strong sensitivity to the attacking angle.

Steel fenders are frequently employed in bridge pier shields to engross collision energy due to vessel impact. However, vulnerability to corrosion is a major drawback in existing steel fenders. To end this, an innovative composite fender structure consisting of corrugated steel and Preplaced Aggregate Fibre Reinforced Concrete (PAFRC) is introduced. Corrugated plates of steel are intended to absorb energy and stiff guard outer panels made with PAFRC exhibit enhanced resistance to impact and ductility. Six steel-PAFRC fenders were prepared with the steel plates of two different thicknesses, where the four top panels of the PAFRC are reinforced with short and long hooked end steel fibres while bottom panels are made with non-fibrous preplaced aggregate concrete (PAC). All steel-PAFRC fenders were tested through a drop weight impact testing device to investigate their impact behaviour and failure mechanism. Collision energy at crack initiation and the ultimate crack of PAFRC panels, crushing deformation of corrugated plates and failure configuration were also examined. Additionally, a numerical model of composite fenders was developed and verified through experimental evidence. Research revealed the crashworthiness of PAFRC panel was higher when compared to the PAC panel. The relative resistance of corrugated plates of steel and the PAFRC panels had a dramatic effect on the composite fender’s impact response.

During the previous major seismic events, the unseating of the bridge superstructure was caused by large relative displacements which exceeded the bridge seat length. Therefore, this paper aims to introduce a multi-level unseating prevention device (MLUPD) to control deck movement. This device is capable of providing lateral resistance force with different performance levels of bridge girder movement in order to limit relative displacement between the superstructure and substructure. The device consists of a combination of a number of springs with different or equal length depending on the bearing type assembled inside each other in parallel to demonstrate multi-levels of stiffness. The design procedure and working mechanism of the device are based on the code of practice. In this study, the MLUPD prototype was fabricated and installed in two different configurations of the steel frame for testing under pushover and cyclic loading to evaluate the MLUPD performance. Additionally, the device performance was also assessed using numerical study. Hence, a constitutive model for the developed MLUPD was derived. Then, the analytical model of the bridge with and without MLUPD device was codified by the finite element program in order to evaluate the seismic performance of the bridge equipped with the developed device. The experimental and finite element results of the MLUPD prototype revealed that the device is capable of unseating prevention through the multi-level performance. In addition, the results indicate that the developed system demonstrated a significant force resistance in two frame configurations. Moreover, the numerical results of bridge time history analysis in terms of girder displacement, pier base shear and drift ratio demonstrated that the bridge seismic behavior is enhanced by utilizing the developed device along with different bearing cases.

The Botan Bridge, built in Siirt Pervari district, was planned to be the country’s longest free cantilever bridge before it collapsed. Free cantilevering is a method of construction where a structure is built outward from a fixed point to form a cantilever structure, without temporary support, using staged cast-in-situ construction. The bridge was designed to connect the Southeastern Anatolia to Eastern Anatolia. It has two piers 105.88 m high and the complete length of the deck is 450 m. Prior to the construction of the bridge, a computer model was generated, however there was deviation from the model during the construction without updating the model to reflect the changes. On December 18, 2018, the bridge collapsed during construction without any casualty recorded. Furthermore, it also suffered a partial collapse when the mid-span on the Begendik side fell into the river. The P1 pier was damaged because the parts falling to P1 were hit. Consequently, It was decided that it had to be demolished and rebuilt. This article investigates the actual cause of the collapse with recommendations for future projects.

A new nonlinear track-bridge random model was established based on OpenSEES, of which the random seismic responses is systematically studied by using probability density evolution method (PDEM). First, a three-dimensional detail nonlinear random dynamic model of the track-bridge coupled system in high-speed railway is established considering the earthquake as the random excitation. The dynamic model is composed with the rail, CRTS II slab ballastless track, the simple supported bridges, bearing, pier and the pile foundation, from which the random dynamic equation of the random model is formulated. In order to evaluate the seismic performance of track structures from a random perspective, the random seismic responses of high-speed railway bridge under random seismic excitations are investigated and analyzed by using the PDEM. Eventually, the Newmark β integration method and the double edge difference method of TVD format are adopted to obtain the random responses involving the probability functions, which can be translated to get the mean value and the standard deviation of responses. Thus, the abundant probability information of seismic responses of the high-speed railway bridge under random seismic excitations can be obtained. The PDF and CDF of the sliding layer are obtained; thus, the failure probability and reliability of different damage grades of sliding layer are obtained. Discussions and significant conclusions on the random dynamic responses are presented.

The objective of this paper is to propose a novel fragility analysis method pertinent to the combination of the least squares support vector machine (LS-SVM) algorithm and JC method for the vulnerability estimation of deep-water high piers located in reservoirs under near-field ground motions. First, the uncertainties associated with the design parameters are considered and the LS-SVM algorithm is adopted to predict the cross-sectional critical curvature values of each damage state of the example pier and determine the probability distributions. Then, a group of finite element models of the example pier is developed using the OpenSees platform for considering the uncertainties related to the design parameters and near-field seismic waves; the Morrison equation is employed to calculate the added mass to simulate the hydrodynamic pressure. Meanwhile, the dynamical responses of the example pier with seven different water depth conditions are investigated using increment dynamic nonlinear analysis along the longitudinal and transverse directions under seismic excitations. Finally, the fragility functions are derived based on the JC method to consider the probability distributions of the cross-sectional critical curvature values and dynamical responses simultaneously; these functions are applied for assessing the damage probability at different damage states of the example pier. It can be concluded that the hydrodynamic pressure plays an important role in influencing the natural vibration period and mode shape of the deep-water high pier. In the slight, moderate, and extensive damage states, the damage probability of the middle-upper and bottom areas of the example pier is relatively large under longitudinal near-field seismic excitation; nevertheless, only the bottom is easily damaged under transverse near-field seismic excitation.

A novel scanning technique using a rotating-head sonar profiler attached to a slider mechanism is presented as a means to directly measure the complex erosion and deposition features of local scour holes developing in clear-water conditions around vertical cylinders mimicking bridge piers. Extensive validation shows that the method produces high-density elevation surfaces to within ≅1.5 ± 2 mm accuracy in a quasi-non-invasive manner. This equates to 0.5 ± 0.7% relative to the flow depth which sonar resolution is well known to scale with. Experimental data from three trials using different cylinder diameters indicate that monitoring of the entire scour hole over time (instead of only the maximum depth as is commonly done in laboratory experiments) can reveal important information about local scour evolution. In particular, results show that the scour-hole volume scales with the maximum scour depth cubed ( V O L − y s 3 ) through three linear regimes. The transition to the third linear regime was found to represent a step change in the scour evolution process. Following the recent theoretical framework proposed by Manes and Brocchini (2015), this change, termed the crossover point, was interpreted as the point where the production of turbulent kinetic energy plateaus which corresponds to a stabilization in the erosive power of the horseshoe vortex. Scour development beyond the crossover point is characterised by a significant reduction in the rate of volumetric scour, relative to the steadily-increasing maximum scour depth. This overall reduction in volume-development is attributed to a balance between erosion from in-front of the pier and deposition around the sides using topography analysis. It is speculated that the existence of the crossover point may help to identify the characteristic length and time scales describing the evolution of local scour, which may be used for modeling purposes.

NSF [EAR1313588]; Taiwan, MOST [107-2116-M-002-001-MY3]; European Union; State of Hungary; European Regional Development Fund [GINOP-2.3.2-15-2016-00009]

Ship detection using optical satellite imagery is of great significance in many applications such as traffic surveillance, pollution monitoring, etc. So far, a lot of ship detection methods have been developed for images covering open sea, offshore area and harbors. Compared to the ship detection in sea and offshore area, it is more difficult to detect ships in inland river due to several challenges. First of all, many ships in inland river are clustered together and hard to be separated from each other. Secondly, ships lying alongside the pier are very likely to be recognized as part of the pier. Thirdly, ships in inland river is usually smaller than those in the sea. A hierarchical method is proposed to detect the ships in inland river in this paper. The Regions of Interest (ROIs) are firstly extracted based on water–land segmentation using multi-spectral information. Then two kinds of ship candidates are extracted based on the panchromatic band. The isolated ships are detected by analyzing the shape of connected components and the clustered ships are detected by using mixtures multi-scale Deformable Part Models (DPM) and Histogram of Oriented Gradient (HOG). At last, a Back Propagation Neural Network (BPNN) is trained to classify the ship candidates using the multi-spectral bands. The experiments using Quickbird satellite images show that our approach is effective in ship detection and performs particularly well in separating the ships clustered together and staying alongside the pier.

Retrofit of existing bridges founded on pile groups can be a challenging, costly, and time-consuming operation, especially when foundation interventions are required. The optimization of retrofit design, and hence of such complicated interventions, may be done by allowing controlled strongly nonlinear response of pile groups and associated energy dissipation mechanisms to develop during seismic loading. Taking advantage of such response may also offer improved seismic performance. Nevertheless, a prerequisite for the application of such rational design concepts is the realistic evaluation of actual stiffness and capacity of pile groups. The latter can be estimated based on in-situ soil testing (e.g. CPT) according to the current state of practice, while the former has been approached until now solely analytically and numerically. This paper proposes a first approach to a simplified stiffness estimation method based on in-situ measurements of lateral vibration response of existing bridges. Estimates of stiffness parameters are obtained with simplified equations of motion, using measurements of the lateral vibration response of a bridge pier and its foundation system to a controlled low-amplitude nondestructive dynamic loading. A numerical study is conducted to evaluate the efficiency of the proposed simplified method and to explore its applicability in real-scale projects., Soil Dynamics and Earthquake Engineering, 148, ISSN:0267-7261, ISSN:1879-341X

The seismic performance assessment of bridges by nonlinear time history analysis using unidirectional spectrum-matched accelerograms is generally adopted in Japan's specifications. However, the simultaneous action of two horizontal components is known to induce a potentially higher inelastic response in steel piers relative to that under unidirectional excitation. In this background, a rising concern within research communities is the bidirectional effect on the risk of bridge failure or damage under a given seismic intensity during the service life of a bridge. In this study, the difference in the risk of steel pier damage/failure between unidirectional ground motion and bidirectional ground motion is assessed using seismic fragility. Fragility curves are constructed by subjecting a single steel pier with various geometric designs to a large number of earthquake ground motions using the incremental dynamic analysis methodology. The study indicates that the damage state of collapse is not changed by bidirectional excitations, whereas the use of bidirectional excitations in less damaging states reduces the bridge seismic performance and induces higher fragility. The response difference is quantified by introducing an equifragility factor. This factor is calculated as the ratio of intensity of the unidirectional input to the bidirectional input, which causes the same fragility caused by the unidirectional counterpart. The constant characteristic value of the equifragility factor provides useful information for considering the bidirectional effect in seismic design.