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Reinforced concrete bridge piers are extremely vulnerable to damage during long-duration ground excitations or main shock-aftershock type earthquakes due to accumulated damage caused by a great number of reversed excursions in elastic-plastic range. However, few studies on fatigue damage of piers can be found in literature. Low-cyclic loading tests of four identical RC bridge piers with high-strength rebar HRB600E (yield strength about 600 MPa) were carried out in this study. One of specimens was taken as the benchmark and was subjected to a conventional load protocol, and the rest was subjected to one, two and three times yield displacement, respectively. The research results showed that the fatigue strength of RC bridge piers tended to drop drastically at about ten cycles and then slowed down gently. It was found that strength degradation rate increased significantly with the displacement amplitude for fatigue tests while the fatigue life decreased dramatically with the displacement amplitude. In particular, when the cyclic loading displacement exceeded 2 times the yield displacement, the fatigue life dropped dramatically. Based on the experimental data, an exponential-type damage model was proposed with the peak lateral force at the first cycle as the coefficient, the cycle count as the base and factor of the loading displacement amplitude as the exponent, which could accurately predict the degraded lateral force of the bridge piers at different constant drifts. An accumulative fatigue damage index was established to evaluate the damage level of bridge piers. [ABSTRACT FROM AUTHOR]

In this study, sacrificial components were incorporated into self-centering railway bridge piers to improve the lateral stiffness. The seismic response of this new detail was investigated. First, the method to compute the initial uplift moment of the self-centering pier is given. In addition, shaking table tests were conducted on a free-rocking pier without sacrificial components, which was used to validate a two-spring numerical model. Good agreement was obtained between the numerical results and experimental data. Furthermore, the validated model was employed to investigate the influence of sacrificial components on the seismic response of rocking piers. For this purpose, two models were developed, with and without sacrificial components. Nonlinear response history analysis was then performed on both models under three historical motions. The results showed that compared to the one without sacrificial components, the rocking pier with sacrificial components has comparable displacement at the top of the pier, and maximum uplift moment at high amplitude motion. Therefore, incorporating sacrificial components into the rocking pier can increase the lateral stiffness at service load and low amplitude frequent earthquakes but can produce comparable response at high seismic excitation. These results provide support for performance-based seismic design of self-centering rocking piers. [ABSTRACT FROM AUTHOR]

• Shear key forces in skew bridges can be dominant at acute corners if gap is closed. • The design connection force in AASHTO could be inadequate in low seismic zone. • It is recommended to increase gap to reduce shear key force in low seismic zone. • Longitudinal motion should be considered to compute the shear key forces. • A SM was developed to estimate the maximum shear key forces in skew bridges. One of the prevalent seismic damage modes of skewed bridges is that the shear keys and/or other transverse retainers at the acute corners suffer severer damages than those at the obtuse corners. In practice, the retainers are usually designed and detailed as structural fuses to protect the substructure and foundation in high seismic zones. However, in low seismic zone, such as seismic zone 1 in AASHTO, they are designed elastic. In this paper, a parameter study was conducted to: (1) investigate the distribution of forces among the shear keys in skewed bridges and (2) evaluate AASHTO's provisions for the minimum connection force of shear keys in low seismic zone. Parameters of interest include skew angle and expansion gap size. An experimentally validated numerical model was employed to model the prototype bridges with exterior shear keys. Nonlinear response history analysis was performed. The results show that when the longitudinal gap is closed for small to moderate gaps, the forces in the keys at the acute corners can be much higher than those at the obtuse corners. This is most likely to occur since the keys should resist the transverse loading along with the impact and friction forces at the abutment-deck interface caused by longitudinal motion. These higher forces of the keys at the acute corners could exceed AASHTO's limit in low seismic zone. To reduce the forces in the keys, it is recommended that the gap be increased in size to avoid abutment pounding, which is an affordable solution in low seismic zone since the increase is expected to be small. Further, a Simplified Method is developed to estimate the maximum connection forces of skew bridges in low seismic zone. Good agreement was obtained between the Simplified Method and the FEM model. Therefore, the Simplified Method may be used for the preliminary design of shear keys. [ABSTRACT FROM AUTHOR]

• Unseating mechanism of a skew bridge is investigated by experiments. • An existed mechanism is modified based on shake table experiment results. • A Simplified Method is developed to estimate the support length of skew bridges. • The Simplified Method is validated by shake table experiment results. • The SM may be used for the preliminary design of bridges with standard gap sizes. In this paper, the unseating mechanism of a skewed bridge during earthquake shaking is investigated. To begin, an existed unseating mechanism in literature, which was proposed by other researchers, is described. The mechanism hypothesizes that under lateral loading, the obtuse corner of the superstructure of a skew bridge engages the adjacent back wall and the superstructure then rotates about this corner, causing large in-plane displacements at the acute corner at the other end of the span, potentially unseating the edge girder. It is then validated using data from a comprehensive set of shake table experiments recently conducted by the author and other researchers. Whereas the experimental data confirms this mechanism as the primary reason for the rotation, it is not the only reason. Impact of the span against the back wall is followed immediately by rebound away from the wall and the span continues to rotate in the same direction in free vibration about the center of stiffness of the substructure. This additional rotation further increases the superstructure rotation and the in-plane displacement of the acute corner. Based on the existed mechanism, a Simplified Method is then developed to estimate the support length requirements of skew bridges. This method, which is based on response spectrum analysis, can consider the closure of expansion gap. The basic procedures are described for the AASHTO's design spectrum, and spectrum of an arbitrary ground motion. A closed form solution is achievable for the former spectrum, while iteration is required for the latter spectrum. The results are then compared with the experimental dataset. It is found that the accuracy of the Simplified Method depends on the gap size. That is: it overestimates the maximum displacements normal to the abutment of skew bridges when the gap is small, accurately estimates when the gap is in a typical range, and underestimates when the gap is large. The underestimation is mainly because the Simplified Method neglects the "bounce back" effect of skew bridges. Therefore, the Simplified Method may be used for the preliminary design of bridges with standard gap sizes, but should be modified to include "bounce back" effect when the gap is large. [ABSTRACT FROM AUTHOR]

• A novel metal rubber bridge bearing is proposed. • Hysteretic curve of the bearing is bilinear with high energy dissipation capacity. • Increase of vertical compressive stress can stiffen the metal rubber bearing. • Loading frequency can have a slight influence on the lateral behavior. • The Bouc-Wen model can capture the hysteretic curve of the proposed bearing. In this paper, a novel metal rubber bearing is proposed as an alternative to the conventional rubber bearings for small- and medium-span highway bridges to solve the aging-related issues of conventional rubber bearings such as chemical degradation and erosion. The bearing is made of porous metal wire by coiling, weaving and cold-pressing to specific shapes. A shear test program is then described on two metal rubber bearings of stainless steel wire with different densities in order to identify the characteristics of hysteretic curves. The effects of shear strain, compressive stress, loading frequency and repeated loading cycles on the hysteretic behavior were investigated. It was found that the lateral hysteretic curves are approximately in bilinear shape, which consists of an initial elastic stage and a post-yield stage. The equivalent damping ratio of the tested bearings was around 20% at 25% shear strain levels and meanwhile increased with the strain levels, indicating an appreciable energy dissipation capacity. In addition, stiffness degradation was observed for the hysteretic curves beyond a certain deformation limit due to the plastic deformation caused by wire delamination and bearing bulging. However, beyond this limit, the bearing could still work as a unit with stable hysteretic behavior. These characteristics make the metal rubber bearing a great candidate for the conventional rubber bearings. It was also found that the hysteretic behavior is related with a variety of parameters such as density, loading frequency and compressive stress. Finally, it was found that the Bouc-Wen model with appropriate input parameters representing the mechanical properties can accurately simulate the hysteretic curves of the proposed bearings. [ABSTRACT FROM AUTHOR]

Precast reinforced concrete (RC) shear walls have attracted significant research efforts due to advantages over the conventional construction methods such as better quality control, shorter construction time and less environmental impact. Research efforts have been dedicated to exploring alternative methods for the connections of precast shear walls. In this paper, a novel partial precast shear wall is proposed, which is made of a precast shear wall with double-legs at the base, and reserved cast-in-place base zone and wall edges. To begin, the design concept of the proposed precast shear wall is described. A comprehensive experiment program is then presented, in which two groups of identical full-scale shear walls were designed, constructed and tested in a cyclic pseudo-static manner in order to investigate the seismic performance of the proposed wall. Each group consisted of three specimens, one cast-in-place and two proposed walls. These two groups of specimens were tested under a high axial load index of 0.3 and 0.4, respectively. The test results indicate that the failure modes of the proposed partial precast walls were similar with those constructed with cast-in-place method. For both axial load indices, the precast walls had comparable seismic performance with the cast-in-place walls in terms of lateral load capacity, stiffness degradation, steel strain behavior, energy dissipation, and residual displacement but better deformability and ductility. In addition, higher axial load indices resulted in decrease in ductility and increase in residual displacements. Moreover, the same precast walls in the same group had similar performance, providing confidence in the repeatability of the test results and stable performance of the proposed walls. It can come to the conclusion that the proposed partial precast shear walls can have comparable and stable seismic performance with the conventional cast-in-place method and hence can be taken as an alternative in practice. • A novel partial precast RC shear wall is proposed. • The proposed partial precast RC shear walls have a good re-centering capacity. • The proposed precast walls have comparable seismic performance with CIP walls. • The proposed precast walls have better deformability and ductility than CIP walls. • Increase in ACR will increase the lateral load capacity and reduce ductility. [ABSTRACT FROM AUTHOR]

It is known that different types of bridge structures exhibit significant variations in the selection of ground motion IMs due to differences in their dynamic characteristics. Additionally, the dynamic characteristics of UHPC ribbed arch bridges differ from those of conventional bridge structures. Conclusions about the seismic fragility of conventional bridge structures derived from previous studies may not be applicable to this specific bridge. In this paper, seismic fragility of UHPC ribbed arch bridges is assessed through the Incremental Dynamic Analysis Method (IDA). For this purpose, an 85m UHPC ribbed arch bridge is selected as the engineering background. The 3-D finite element model of the bridge was established using OpenSees. Subsequently, 12 far-field and 12 near-field ground motion records were selected for nonlinear time-history analysis of the structure. Damage indexes for the arch ribs and tie beams were defined according to the seismic response characteristics of bridge, with the sectional curvature of five locations within these components serving as engineering demand parameters (EDPs). These EDPs were subjected to logarithmic regression analysis with respect to 8 ground motion intensity measures (IMs), aiming to evaluate the efficiency, practicability and proficiency of each IM, and to identify the optimal ground motion IM for this type of bridge. Finally, fragility curves for the arch ribs and tie beams were developed based on the fragility method, pinpointing the seismic vulnerable components of the bridge and assessing the overall seismic performance of the structure. The results indicate that the spectral acceleration at the fundamental period of the structure SAT1 is the optimal IM for fragility analysis of this bridge, followed by the effective peak acceleration EPA and acceleration-based IMs. In addition, under transverse ground motion excitations, the most vulnerable component of the bridge is found to be the E-type tie beam, followed by the springing position of the exterior arch rib. Within the given range of ground motion intensity, the bridge damage will be concentrated on non-structural components (tie beams and bridge deck). The results can provide the guidance for the seismic vulnerability assessment of UHPC ribbed arch bridges. • Seismic fragility of UHPC ribbed arch bridges is assessed through the IDA method. • The optimal IM is spectral acceleration at the structural fundamental period SAT1. • The most vulnerable component of the bridge is found to be the E-type tie beam. • Seismic damage to the bridge is concentrated on the non-structural components. [ABSTRACT FROM AUTHOR]

• Corrosion in the rebars was uneven by the electromechanical method. • Low-level corrosion (about 7.2%) can severely reduce capacity of precast RC column. • Retrofit should be performed on the precast RC columns at low-level of corrosion. • Corrosion has worse effect on deformability than strength of precast columns. • CFRP jackets alone are not recommended to retrofit the columns of higher corrosion. Precast reinforced concrete (RC) bridge columns are critical substructure components for Accelerated Bridge Construction (ABC), which attracts significant attention all over the world in recent decades. However, seismic behavior of precast RC bridge columns in corrosive environment and related retrofit methods are rarely studied. To fill out this knowledge gap, in this study, four, 1/4-scaled precast RC bridge columns of various corrosion levels were designed, constructed and tested in a pseudo-static manner to gain in-depth understanding of corrosion on the seismic behavior of this type of columns. Two of these columns with higher corrosion levels were retrofitted with carbon fiber reinforced polymer (CFRP) fabrics in the plastic hinge zone to assess the effectiveness of this retrofit measure. Corrosion levels of the specimens were obtained through an electrochemical method to accelerate the corrosion process at the plastic region. It was found that corrosion in the reinforcement was uneven across the section and was much severer at the joint of precast bridge columns. It was also found that even the low corrosion level of longitudinal reinforcement (i.e. 7.2%) can result in a significant decrease (i.e. >15%) in the lateral load capacity, energy dissipation, ductility and ultimate displacement. Hence, the retrofit of corroded precast RC bridge columns should be performed at low-level of corrosion. The test results also indicate that corrosion has more adverse effect on the ultimate displacement and ductility than the strength. In addition, retrofitting bridge columns of higher corrosion levels (i.e., >10%) using CFRP jackets could effectively protect the columns from damage in the plastic hinge zones. However, the damage pattern was shifted to fracture of the longitudinal rebars at the column-footing interface, resulting in substantial reduction in the ultimate displacement capacity. Therefore, it is not recommended to retrofit precast RC bridge columns of high corrosion level using CFRP jackets alone. [ABSTRACT FROM AUTHOR]

To break through the three major technical bottlenecks of traditional long-span arch bridges, which are excessive self-weight, high cost and difficult construction, a new steel-ultra high performance concrete (UHPC) composite truss arch bridge scheme and a matching cyclic construction method were proposed. The main arch can be divided into several times for closure from the inside out. Special transverse connection devices need to be installed between the arch ribs constructed with successive closures by step. The devices can not only ensure the stability of the arch ribs constructed subsequently, but also do not cause serious stress superposition on the already closed arch ribs. Therefore, sliding connectors for the cyclic construction of new arch bridges and the corresponding simplified modeling method were proposed in this paper. Subsequently, the working mechanism was analyzed, and the design method was proposed. Finally, the feasibility of sliding connectors and the correctness of the corresponding design method were verified by the experiment. The results indicate that it is necessary to install a transverse sleeve structure in the sliding connector, which plays a key role in transverse adjustment. The design of key dimensions in sliding connectors is controlled by the maximum vertical and longitudinal displacements of the inner arch. The outer arch could slide freely under the premise of ensuring stability, and the mechanical superposition response of the inner arch was relatively small. For the inner arch, the vertical displacement at the crown only increased by 10.94 %, and the maximum compressive stress in the UHPC arch ribs only increased by 16.3 %. The sliding connector also has the potential for further optimization to achieve smaller stress superposition. • Sliding connectors for the cyclic construction of steel-UHPC composite truss arch bridges and the corresponding simplified modeling method were proposed. • For the sliding connector, the working mechanism was analyzed, and the design method was proposed. • The feasibility of sliding connectors and the correctness of the corresponding design method were verified by the experiment. • For the inner arch, the crown deflection only increased by 10.94 %, and the maximum compressive stress in the UHPC arch ribs only increased by 16.3 %. [ABSTRACT FROM AUTHOR]

Accurate understanding and quantification of the risk to critical infrastructure posed by future large earthquakes continues to be a very challenging problem. Earthquake phenomena are quite complex and traditional approaches to predicting ground motions for future earthquake events have historically been empirically based whereby measured ground motion data from historical earthquakes are homogenized into a common data set and the ground motions for future postulated earthquakes are probabilistically derived based on the historical observations. This procedure has recognized significant limitations, principally due to the fact that earthquake ground motions tend to be dictated by the particular earthquake fault rupture and geologic conditions at a given site and are thus very site-specific. Historical earthquakes recorded at different locations are often only marginally representative. There has been strong and increasing interest in utilizing large-scale, physics-based regional simulations to advance the ability to accurately predict ground motions and associated infrastructure response. However, the computational requirements for simulations at frequencies of engineering interest have proven a major barrier to employing regional scale simulations. In a U.S. Department of Energy Exascale Computing Initiative project, the EQSIM application development is underway to create a framework for fault-to-structure simulations. This framework is being prepared to exploit emerging exascale platforms in order to overcome computational limitations. This article presents the essential methodology and computational workflow employed in EQSIM to couple regional-scale geophysics models with local soil-structure models to achieve a fully integrated, complete fault-to-structure simulation framework. The computational workflow, accuracy and performance of the coupling methodology are illustrated through example fault-to-structure simulations. [ABSTRACT FROM AUTHOR]

Prefabricated post‐tensioned pre‐stress concrete (PC) T‐girder is one of the common structural forms for bridge superstructure to achieve better quality control, higher construction speed and lower downtime to the transportation system. However, vertical cracks are frequently observed at the web of girder ends after prestress is applied, which could impose an adverse effect on the durability of girders when exposed to aggressive environment. In this paper, the mechanism of this cracking pattern and corresponding countermeasures were investigated by a numerical study as well as practical engineering applications. To begin with, a nonlinear three‐dimensional (3D) finite element model was developed to simulate a typical PC T‐girder in the platform of ABAQUS. The model was loaded based on the sequence of post‐tensioning. It was found that the vertical crack pattern is caused by the large friction resistance and bond strength at the contact surface between the girder and supporting steel pedestal as well as the stress concentration at the girder ends due to the cambering effect of girder during the application of prestress. In addition, a practical method was proposed to control this crack pattern by introducing an isolation cushion made of a thin wood piece to the bottom of girder end. The reliability of this method was verified by numerical analysis and engineering practice. Therefore, it can be used to control vertical cracks at the ends of prefabricated post‐tensioned PC bridge T‐girders during construction. [ABSTRACT FROM AUTHOR]

A novel steel inner core-ultra high performance concrete (UHPC) composite box girder structure is proposed, which is lightweight, economical and low-carbon emission. In this proposal, the steel inner core serves as both the load-bearing structure and the UHPC internal formwork. Eliminating the installation of longitudinal ribs in the steel inner core greatly reduces the amount of welding, minimizes sources of fatigue damage, and simplifies construction. The UHPC is externally wrapped around the steel inner core to ensure the structural durability. When the novel box girder is applied to the incremental launching continuous girder structure with a span of 70 m, the technical index per square meter of the main girder is: 163 kg of steel, 0.242 m3 of UHPC, and a self-weight of 820 kg. With the same span, the novel box girder structure exhibits significant advantages in comprehensive performance compared with other types of main girder structures. The flexural behavior of the novel box girder was investigated through a four-point bending experiment and the cracking characteristics of the test specimen on the bottom plate under different reinforcement configurations were analyzed. The test results showed that the amount of reinforcing bars in UHPC had a significant impact on the development of cracks. When arranged with a diameter of 16 mm and a spacing of 100 mm, the overall distribution of cracks was short and fine, and the crack resistance strength was 1.56–1.80 times that of the reinforcement configuration with a diameter of 16 mm and a spacing of 200 mm. The preliminary test and analysis results suggest that the proposed composite box girder can be taken as a new structural option for medium to large span bridges ranging from 40 m to 100 m. • Steel inner core-ultra high performance concrete composite box girder structure. • Conceptual design of a 70 m incremental launching girder. • Comparison of technical and economic indicators. • Preliminary flexural tests of the steel inner core-UHPC composite box girder. • Nominal tensile stress-maximum crack width relationship. [ABSTRACT FROM AUTHOR]

In this study, a 1/100-scale shaking table experiment was designed and conducted for a multi-tower cable-stayed bridge in order to investigate its seismic response characteristics with consideration of seismic pounding between the main and approach bridges. The test parameters include the expansion gap size and period ratio between the main bridge and the approach bridge. Both the near-field and far-field ground motions were selected to excite the model. Test results indicate that the seismic response of multi-tower cable-stayed bridges is very sensitive to the gap size and a reasonable gap size of expansion joint can mitigate the pounding effect on structural response. In addition, a period ratio close to 2:1 resulted in the most significant pounding effect and should be avoided in the design stage to reduce the collision risk. Moreover, seismic pounding could significantly amplify the relative displacement between the pier and girder of the main bridge elevating the risk of girder unseating. The test results can provide a valuable reference for the seismic design of cable-stayed bridges with multi-tower. • Shake table tests were conducted on a multi-tower cable-stayed bridge with seismic pounding. • Seismic response of multi-tower cable-stayed bridges is very sensitive to the gap size. • A reasonable gap size of expansion joint can mitigate the pounding effect on the bridge response. • A period ratio close to 2:1 resulted in the most significant pounding effect. • Seismic pounding could significantly amplify the relative displacement between the pier and girder. [ABSTRACT FROM AUTHOR]

• Failure mechanism of river-crossing simply-supported girder bridge was investigated when soil liquefaction is considered. • Finite element model was developed considering simply-supported girder bridge and surround sites as an integral system. • Investigation of pile–pier displacement demand and failure mode. • Bending pattern of pile–pier and failure mechanism. • Sliding bearing behavior under near-fault ground motions. Soil liquefaction induced by strong earthquake could cause severe failure to bridges, particularly for river crossing simply-supported girder bridges. Consequently, it is an urgent task to clarify the influence of soil liquefaction on the seismic failure of this bridge-ground system. To this end, two-dimensional finite element (FE) simulation method focusing on liquefiable site-structure was validated based on a published centrifuge test at first. Then 2 refined FE models were established for a typical river-crossing simply-supported girder bridge with the only difference whether considering site liquefaction. Near-fault ground motions were selected for nonlinear dynamic analysis. Seismic responses of two models were compared to investigate the influence of soil liquefaction on bridge failure mode. The comparison results indicated that soil liquefaction significantly changed seismic response of bridge-ground system, such as site displacement performance, pile–pier displacement demand, pile–piers bending mode, sliding bearing deformation, leading to higher bridge failure risk and change of failure mode. [ABSTRACT FROM AUTHOR]

• An innovative formula of plastic hinge length of RC round-ended hollow columns with a variable section was proposed, in which plastic stress extension and bond-slip of longitudinal rebar were included. • Compared to the rectangular columns with a uniform section, the effect of the bottom solid segment, chamfer, and variable section were considered in the lengthened plastic hinge length of round-ended columns. • The suggested formula is more applicable to estimate the plastic hinge length of columns with a uniform or variable hollow section than the existing models. In the ductile design, it is an essential task to accurately estimate the equivalent plastic hinge length of a reinforced concrete (RC) column. The plastic behavior of a RC hollow column is influenced significantly by tension shift and bond-slip according to the test results, which hasn't yet received adequate attention in the existing models of equivalent plastic hinge in the literatures. Few publications and even no explicit provision in the current codes provide the method to compute the plastic hinge of hollow RC columns, especially those with a variable section. To bridge this knowledge gap, in this study, based on the equivalent principle of plastic displacement, an innovative formula of equivalent plastic hinge length is derived for the hollow columns, which considers both the effects of plastic tension shift and bond-slip based upon the authors' previous research on solid columns. The quasi-static tests on two rectangular and two round-ended hollow columns were conducted to calibrate the undetermined parameters of the proposed formula. The accuracy and applicability of the proposed formula were then investigated based on the available test results of 30 rectangular and 3 round-ended hollow columns in literature. The results show that different slip behavior leads to distinct plastic deformation between these two types of hollow columns. Compared to the rectangular columns with a uniform section, the plastic hinge length of round-ended columns is longer due to the presence of the bottom solid segment, chamfer, and variable section. For both types of hollow columns, the equivalent plastic hinge region increases with the specimen length, section height , and strain penetration. The comparison suggests that the proposed formula is more appropriate to calculate the plastic hinge length of hollow columns with a uniform or variable section than the existing models. [ABSTRACT FROM AUTHOR]

A novel partly precast shear wall was proposed in this study to accelerate construction and further reduce the weight of precast components for high-rise building structures. The proposed wall consisted of double precast edge members and a central cast-in-place (CIP) member. The rebar splice was achieved by the grout-filled sleeve connection for the precast members and lap splice connection for the CIP member. The seismic performance of the proposed wall was investigated through a full-scale experimental program, in which three specimens were designed and tested under the combination of a constant axial load and cyclic loads, including two identical proposed walls and a CIP wall as a reference. The axial load was applied to achieve a high axial load ratio of 0.5. Based on the test results, it was found that the proposed walls were subjected to similar damage progression and failure mode with the CIP wall. All failed due to concrete crushing, shear cracking and rebar buckling at the base corners of walls. The only difference was that the proposed walls would experience additional vertical cracks along the interface between the precast and CIP zones due to insufficient bond strength between at the interface. It was also found that under the high axial ratio of 0.5, the proposed walls would have comparable seismic performance with the CIP wall in terms of deformability, ductility and lateral load capacity. In addition, the two identical proposed wall had similar seismic performance indicating the good repeatability of test data and stable performance of the walls. Therefore, the proposed walls can have satisfactory seismic performance during a seismic event and could be an effective alternative method for the CIP walls if designed appropriately. • A novel partial precast RC shear wall was proposed. • The proposed walls had similar failure progression and mode with the CIP wall. • The proposed partly precast RC shear walls had a good re-centering capacity. • The proposed precast walls had comparable seismic performance with CIP walls. • The GS connection could provide a reliable connection for the proposed wall. [ABSTRACT FROM AUTHOR]

• Full-scale pseudo-static tests were conducted on Equal Strength Mild Steel Tenons. • The tested ESMSTs have satisfactory seismic performance and good fatigue behavior. • The numerical model can accurately reproduce the behavior of tested ESMSTs. • The case study shows that the ESMSTs can have more than 25% less displacements. • The ESMSTs can work effectively and efficiently in long-span railway arch bridges. In this paper, Equal Strength Mild Steel Tenons (ESMSTs) have been developed as a candidate for displacement restraining device of long-span railway arch bridges. They are made of a cheap and easily fabricated material, low carbon mild steel. The geometry is designed according to the principle of equal strength beam to make full use of the ductile deformation of mild steel, increase the energy dissipation capacity and alleviate damage concentration. To begin, the design concept of ESMST is given followed by the derivation of the theoretical formula of the mechanical properties with the vertical free mechanism which is of no vertical load to guide the design. A pseudo-static experiment program is then presented for two full-scale 2.5 m tall ESMSTs. Besides, a rigorous 3D numerical model was developed in ABAQUS to reproduce the behavior of ESMSTs to guide the design of ESMST in future application. Finally, a case study is presented for the application of ESMST in one of typical long-span railway arch bridges to evaluate its efficiency and effectiveness. The test results indicate that the tested ESMSTs can meet the demands of the long-span railway arch bridges for high initial stiffness, energy dissipation and deformability under strong earthquake action. It was also found that the ESMST had good fatigue performance. In addition, the developed numerical model in ABAQUS can accurately reproduce hysteretic behavior of the ESMST and hence can be used with confidence in the future to guide the design of ESMSTs. Results from the case study show the ESMSTs can work effectively and efficiently in reducing the response of long-span railway arch bridges without imposing much additional demand on the substructure. Findings of this study can provide guidance on the design of ESMSTs as well as support for the application of the ESMSTs in long-span railway arch bridges. [ABSTRACT FROM AUTHOR]

Economical laminated rubber bearings have been widely utilized in highway bridges for their exceptional performance under service conditions. These bearings effectively mitigate seismic responses during earthquakes through shear deformation or sliding, contingent upon their bonding methods, whether bonded or unbonded. Nevertheless, past seismic events have underscored vulnerabilities, with unbonded laminated rubber bearings susceptible to excessive displacement and bonded bearings prone to fracture during large earthquakes. To address these seismic deficiencies and improve bridge seismic performance, a novel controllable sliding laminated rubber bearing (SC-LRB) is proposed in this study. The SC-LRB seamlessly integrates the shear-deforming behavior of bonded laminated rubber bearings (B-LRB) with the frictional sliding behavior of unbonded bearings (U-LRB). A quasi-static experiment was initially conducted to investigate the cyclic behaviors of the SC-LRB, leading to the development and calibration of the numerical model for the bearing. Subsequent nonlinear time history analyses were carried out to evaluate the influence of SC-LRBs on the seismic performance of bridges. Results indicate that, with its three-stage working mechanism (pre-sliding, sliding, and post-sliding), the SC-LRB exhibits a friction-shear collaborative behavior, effectively balancing the energy dissipation and recentering capacities of the bearing during earthquakes. Bridges equipped with the SC-LRB demonstrate an ability to maintain balance between controlling bearing displacements and isolating pier seismic demands. The proposed SC-LRB presents promising potential for enhancing the seismic resilience of highway bridges. • A novel sliding-controllable laminated rubber bearing (SC-LRB) is proposed. • Experimental study is conducted to evaluate the hysteretic behavior of SC-LRB. • The proposed SC-LRB shows a sliding-shear collaborative working mechanism under seismic loads. • The balanced energy dissipation and recentering performance of bridges can be achieved by using the proposed SC-LRB. [ABSTRACT FROM AUTHOR]

This paper aims to elucidate the rate-dependent behavior of 304 + Q235 bimetallic steel under intermediate strain rates. Tensile tests were conducted on 18 sets of specimens to obtain the engineering stress-strain curves at various strain rates. The experimental results demonstrate that the strain rate significantly influences both the yield strength and ultimate strength of the 304 + Q235 bimetallic steel, albeit with different trends. The yield strength exhibits an upward trend with increasing strain rates, whereas the ultimate strength demonstrates a downward trend. Additionally, the strain-hardening effect diminishes proportionally with the increase in strain rate. The parameters of the Cowper-Symonds model associated with the dynamic yield strength increase factor (DIF y) were determined based on the experimental findings. A bilinear rate-dependent constitutive model was established to accurately predict the dynamic ultimate strength increase factor (DIF u) of 304 + Q235 bimetallic steel. The established bilinear model was utilized to enhance the Johnson-Cook model for accurate prediction of the true stress-strain behavior of 304 + Q235 bimetallic steel under intermediate strain rates. The calculated results obtained from the modified Johnson-Cook model exhibit good agreement with the experimental results. • The behaviors of stainless-clad bimetallic steel at intermediate strain rates were revealed by dynamic tensile tests. • The parameters associated with C-S models were presented for the yield strength of stainless-clad bimetallic steel. • A bilinear rate-dependent constitutive model was proposed for the ultimate strength of stainless-clad bimetallic steel. • The J-C model was improved to predict the behaviors of stainless-clad bimetallic steel at intermediate strain rates. [ABSTRACT FROM AUTHOR]

Nowadays precast reinforced concrete (PRC) piers have found increasing application in bridge project, due to their favourable advantages such as significant improvement in quality, reduction in construction period, less environmental impact and traffic disturbance. Seismic performance of PRC piers highly depends on the design and detailing of the pier-foundation connection. Due to limited knowledge, the application of PRC piers is restricted to low-seismic regions while is rarely in high-seismic regions. In this paper, an emulative connection method is proposed for PRC piers which combines conventional grouted splice sleeves (GSS) for the longitudinal bar splice and a grouted central tenon (GCT). To begin with, a cyclic pseudo-static experiment was performed on three piers to evaluate the seismic performance, including one CIP pier, two PRC piers with the conventional GSS and proposed GSS-GCT connections, respectively. It was found that the GSS-GCT connection could be an effective solution since it apparently increased the lateral load and energy dissipation capacities and reduced the residual displacement. Moreover, inspired by the shear-induced slip observed during the test, a fiber-based finite element model is developed for PRC piers, which is, first-of-its-kind, capable of accounting for cyclic rebar bond-slip degradation, dowel action and friction. Good agreements are obtained between the numerical and experimental results. Finally, the superior seismic performance of the proposed method is confirmed by the capacity response spectrum method. [ABSTRACT FROM AUTHOR]

• The unfavorable input directions for the test model were identified through tests. • The seismic collision is non-uniform at the joint and hits the corners frequently. • The collision could induce significantly large in-plane rotation of the bridges. • The maximum rotation decreased with the gap size regardless of the input motions. • The pulse-like near-fault motions are most detrimental to curved bridges. It is well-known that curved bridges are vulnerable to girder unseating during strong earthquakes. This is mainly attributed to its irregular geometry and seismic pounding. In this paper, a shake table experiment was designed and conducted on a 1/25-scale model to investigate the influence of collision between adjacent girders on the seismic response of curved bridges. For this purpose, two curved bridges with an expansion joint in-between were taken as the engineering background. Three historical records including a near-fault pulse-like record, a non-pulse-like record and a far-field ground motion were used to excite the test model. The seismic responses of the tested curved bridges were discussed in detail. Impact forces were measured by three load cells installed at the expansion gap joint. To begin with, the model was excited by the near-field pulse-like record in a variety of input directions without seismic collision to identify the most unfavorable input angle of the ground motions. It was found that for the test model, the secant direction of the adjacent two piers of the single-span segment is the most unfavorable input angle for seismic excitations. It was also found that the collision frequently occurred at the corners of the girders and was non-uniform along the contact surface. In addition, the girder-to-girder collision could induce significantly large in-plane rotation of the adjacent bridges, which could substantially increase the global displacement demands of the bridges. Furthermore, the maximum total impact forces increased with the gap size from 1 mm to 2 mm and then decreased with the gap size from 2 mm to 4 mm. However, the maximum in-plane rotation decreased with the gap size from 1 mm to 4 mm regardless of the input motions. Compared with the non-pulse-like near-fault motions, the pulse-like near-fault motions can result in higher in-plane rotation and force demands due to their velocity pulses and hence are more detrimental to curved bridges. [ABSTRACT FROM AUTHOR]

• Five 1/10 scale SC-PSBC specimens were tested under different loading directions. • The oblique loading caused significant damage to the outmost corners of section. • The backbone curves of the SC-PSBCs were approximately elastic-perfectly-plastic. • The oblique loading caused significantly larger residual displacements. • Design without consideration of oblique loading is nonconservative for SC-PSBCs. Self-centering precast segmental bridge columns (SC-PSBCs) have been intensively investigated in the past decade as one of prefabricated bridge components to expedite construction and improve seismic resilience. However, the application of SC-PSBCs is limited to the low seismicity areas due to insufficient knowledge about their seismic performance. In particular, the behavior of SC-PSBCs is not clear under multi-directional seismic excitations. In order to investigate the effect of lateral loading directions on the seismic performance of SC-PSBCs, five 1/10-scale identical SC-PSBC specimens with rectangular hollow sections were designed and tested under lateral cyclic loading and a constant vertical load. Each specimen was loaded at a specific angle with respect to the weak axis of the column section. The loading angles included 0, 30, 45, 60, and 90 degrees. The seismic performance of the specimens was evaluated and discussed using the test results. It was found that the SC-PSBC specimens were of good ductility, and the favorable self-centering capacity was obtained under orthogonal loading directions. Only considering the orthogonal loading direction in the design of SC-PSBCs is non-conservative since it may underestimate the local damage and residual displacement. The extent of prestress loss in each strand was very sensitive to the relative distance to the neutral axis depending on the loading directions. The equivalent viscous damping ratios of SC-PSBCs were in the range from 0.151 to 0.198 at a drift ratio of 4.0%. [ABSTRACT FROM AUTHOR]

• Electrochemical method can result in non-uniform corrosion level among the rebars. • Low level of corrosion in bridge column still results in flexural failure mode. • Corrosion can cause substantial reduction in seismic capacity of bridge columns. • CFRP fabric jacket can improve seismic behavior of corroded bridge columns. • CFRP jackets could not improve the lateral strength of corroded columns. Seismic damage mitigation of corroded reinforced concrete (RC) bridge columns in marine environment will be an impending problem in many countries in which a mass of bridges have been constructed for 20 or more years. In this paper, cyclic pseudo-static tests were conducted on three 1/4-scaled RC column specimens with and without retrofit by carbon fiber reinforced polymer (CFRP) fabric in order to investigate seismic performance of low-level corroded columns and the efficiency of CFRP as a retrofit measure. The first specimen was designed with normal design details of Chinese specifications, which worked as a reference. The second and third columns were both corroded with a target of low-level corrosion in the plastic hinge zone using an electrochemical method. Meanwhile, the third column was retrofitted by CFRP jackets in the plastic hinge region. The experimental results were then employed to evaluate the damage process, failure mode, displacement ductility, energy dissipation, lateral resistance strength, and residual displacement of each specimen. The results show that although low level of corrosion in the tested columns, the displacement ductility was significantly reduced due to weakened confinement of the corroded transverse rebars and reduced area of the corroded longitudinal bars. In addition, retrofitting the column using CFRP fabric jackets could significantly increase the displacement ductility and reduce the residual displacement to some extent. It is worth noting that retrofitting of corroded column using CFRP jackets did not improve the lateral strength. [ABSTRACT FROM AUTHOR]

The utilization of Fiber-reinforced concrete (FRC) in the construction of Precast segmental concrete bridges (PSCBs) is progressively increasing. The design of joints among precast members can considerably impact the overall integrity and safety of the structure. Consequently, accurately estimating the shear capacities of FRC joints has become critical for evaluating the safety of PSCBs structures. However, the effectiveness and efficiency of formulas or models intended for prediction of the shear capacities of joints with normal concrete are unknown in predicting the shear capacities of FRC joints. In this study, the machine learning (ML) algorithms are employed to predict the ultimate load of FRC joints, utilizing a database of 192 push-off test results. Three individual models (Lasso, SVM, and KNN) and three ensemble models (RF, GBDT, and XGBoost) were developed for estimating the ultimate load. The GridSearchCV technique was utilized for parameter optimization based on the training set, in conjunction with a five-fold cross-validation method. A comparative study revealed that the XGBoost ensemble model surpassed other models, with a predictive performance ranking as follows: XGBoost > GBDT > RF > KNN > SVM > Lasso. The best-performing XGBoost model achieved performance metrics of R 2 = 0.964, MAE = 41.318 kN, RMSE = 56.760 kN, and MAPE = 14.228%. The superior reliability of the XGBoost ensemble model was further validated through comparisons with current design codes and existing models. As ML-based models are typically black-box models, the SHapley Additive exPlanations (SHAP) method was employed to explicitly link the predicted output to the inputs. Based on SHAP results, confining stress (CS), depth of shear key (D), compressive strength of concrete (f cu), total height of joints (H), and height of flat part (H sm) recognized as the crucial parameters affecting ultimate load. • This study applies ML algorithms to predict the ultimate load of Fiber-Reinforced Concrete joints for the first time. • The performance of six ML algorithms, including Lasso, SVM, KNN, RF, GBDT, and XGBoost, was evaluated and compared. • this study compares the performance of machine learning models with design code provisions and other models. • The Shapley Additive Explanations method was used to identify crucial parameters affecting ultimate load. [ABSTRACT FROM AUTHOR]

Highlights • A new optical sensor system – Discrete Diode Position Sensor (DDPS) – is presented. • It allows measuring building transient and residual earthquake interstory drift. • Reliability and accuracy of the DDPS are evaluated through shake table testing. • The capability to evaluate in-structure accelerations from DDPS is demonstrated. • DDPS system optimization is investigated and two solutions are finally proposed. Abstract Interstory drift (ID) is a key response parameter for buildings subjected to lateral loads and is used to define performance-based limit states, allowable deformations and damage states in a number of seismic design codes and standards. An ability to rapidly and accurately measure both transient and residual ID during an earthquake would provide important observables for understanding the seismic demands and post-earthquake condition of a building. Accurate retrieval of ID from accelerometer-based instrumentation systems can be very challenging, if not impossible, as a result of instrumentation limitations and the post-processing associated with strong motion accelerometer data. This is particularly true for the case in which residual drifts occur during inelastic building response. In the study presented herein, a newly developed optical sensor system, designed specifically for directly measuring both transient and residual ID, was experimentally evaluated through shake table testing and computational simulations. The ability of the sensor to accurately measure ID is demonstrated and key operational considerations for sensor system deployment are examined through a model-based investigation. [ABSTRACT FROM AUTHOR]

A novel built-in elastomeric pad was incorporated into the plastic hinge zone of precast bridge columns with grouted corrugated duct connection to improve its seismic performance. Appropriate energy dissipation and minimal local concrete damage are expected in the innovative precast reinforced concrete (RC) columns. Four 1/4-scaled bridge column specimens were designed and tested under constant axial compression force and cyclic lateral loads to evaluate the feasibility and effectiveness of the proposed concept. Detailed experiment results were compared and discussed. The testing results showed that the main seismic index of precast RC bridge columns with grouted metal corrugated duct connection was similar to that of the cast-in-place bridge columns. It was also found that the precast RC column with a built-in elastomeric pad in the plastic hinge zone effectively minimized local concrete damage at the bottom of bridge columns and increased the energy dissipation capacity. The laminated elastomeric pad is recommended to be applied in the precast bridge column to maintain necessary initial stiffness and energy dissipation capacity and to avoid lateral bulge of single thick rubber. Excessive buckling and shear deformations of longitudinal rebars should be prevented by inserting a rectangular or square steel tube at the center of the elastomeric pad. • A built-in elastomeric pad was incorporated into the plastic hinge zone of precast bridge columns. • Quasi-static cyclic tests were performed on four bridge column models. • Seismic performance of precast bridge columns with built-in elastomeric pads was satisfactory. • Excessive buckling and shear deformations of unbonded longitudinal rebars should be prevented. [ABSTRACT FROM AUTHOR]

• Quasi-static test on hollow RC bridge piers with constant and varied vertical load. • Hollow thin-walled RC piers experienced a mixed flexure-shear damage progression. • Both specimens collapsed as a result of the flange local compression buckling. • The specimen collapsed much severer under variable axial load. • Valuable dataset can be used to validate advanced numerical modeling techniques. This study aims to investigate the seismic behavior of thin-walled rectangular hollow reinforced concrete (RC) bridge piers through quasi-static cyclic tests. For this purpose, two identical 1:12 scale specimens were designed and tested under different loading protocols. One specimen was subjected to displacement-controlled cyclic lateral loading with a constant axial load, and the other to the same lateral loading history, but with a variable axial load. The behavior of both specimens was evaluated in terms of the damage progression and failure mode, concrete crack width, hysteretic response, backbone curve, and residual displacement. The results revealed that both specimens experienced a mixed flexure-shear damage progression from the first crack through collapse. Flexural cracks were first observed in the flange surfaces, followed by the development of shear diagonal cracks in both web surfaces. Meanwhile, both specimens exhibited stable hysteretic behavior. Then, concrete spalling and longitudinal bar buckling were concentrated at the corners of the flanges due to the shear lag effect. Eventually, both specimens collapsed as a result of the flange local compression buckling. In addition, the specimen under a variable axial load collapsed much severer than the one under a constant axial load. Ultimate drifts of the specimens under a constant or variable axial load were 2.25% and 2%, respectively. This experiment provides valuable dataset for validating advanced numerical modeling techniques for thin-walled rectangular hollow RC piers, especially the data points in the collapse stage. [ABSTRACT FROM AUTHOR]