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Typical small-to-medium-span highway bridges in China are often installed with economical laminated-rubber bearings that allow for thermal movement of girders and concrete shear keys that restrain transverse girder displacement. However, the damage investigation after the 2008 Wenchuan earthquake had shown that sliding between the girder and the la...
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... which six were constructed according to the common details in China. The lateral cyclic loadings were applied to the specimens during the tests. The test results showed that the specimens with common details displayed typical shear failure with major cracks diagonally stretching downward. The shear failure progress of Unit 1A specimen is seen in Fig. 3. Based on the test results, a simplified hysteretic model (Fig. 4) for typical shear keys with shear failure was proposed, considering the contributions of concrete and steel materials. Compared with the previously mentioned model pro- posed by Megally et al. (2003), the simplified model assumed that the unloading stiffness and ...
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... The selected case study is a three-span skewed bridge that presents the typical configuration of a Chilean highway bridge, i.e., precast prestressed concrete girders supported on laminated elastomeric bearings, a continuous RC deck, multi-column bents, and Energy-dissipation devices work as structural fuses, concentrating the seismic damage and maintaining the main structural components with minor or no damage. Although several studies have been carried out to evaluate the seismic performance of bridges with hysteretic dampers, they have been focused on unidirectional hysteretic dampers applied only in the transverse direction [17,18], which in practice can be materialized as metallic dampers, such as X-shaped steel dampers [19], buckling-restrained braces [20][21][22][23][24][25], or pipe dampers [26], among others. On the other hand, research analyzing the effect of bidirectional hysteretic dampers on the seismic performance of skewed bridges is limited. ...
... In previous sections, hysteretic dampers were considered to act on both principal directions of the bridge (i.e., longitudinal and transverse). On the contrary, this section assesses the performance of unidirectional dampers acting only in the transverse direction since this direction has been commonly proposed in various research on highway bridges [17,85]. Figure 9 shows the probability of exceeding a performance level for different hazard levels when using only transverse metallic dampers. ...
... This study provides new evidence that unidirectional hysteretic dampers, which are placed only in the transverse direction, as suggested by other researchers [17], are insufficient for achieving desired performance levels. The probability of damage increased by at least a factor of 2.0 when unidirectional dampers were considered instead of bidirectional dampers. ...
Bridges are one of the most critical and costly structures on road networks. Thus, their integrity and operation must be preserved to prevent safety concerns and connectivity losses after seismic events. Recent large-magnitude earthquakes have revealed a series of vulnerabilities in multi-span highway bridges. In particular, skewed bridges have been severely damaged due to their susceptibility to developing excessive in-plane deck rotations and span unseating. Although seismic design codes have been updated to prescribe larger seating lengths and have incorporated unseating prevention devices, such as shear keys and cable restrainers, research on the seismic performance of skewed bridges with passive energy-dissipation devices is still limited. Therefore, this study focuses on assessing the effectiveness of implementing hysteretic dampers on skewed bridges. With that aim, dampers with and without recentering capabilities are designed and incorporated in representative Chilean skewed bridges to assess their contribution to seismic performance. Three-dimensional nonlinear finite element models, multiple-stripe analysis, and fragility curves are utilized to achieve this objective. The results show that incorporating bidirectional dampers can effectively improve the seismic performance of skewed bridges at different hazard levels by limiting in-plane deck rotations independently of their skew angle. Additionally, the influence of external shear keys and damper hysteretic behavior is analyzed, showing that these parameters have a low influence on bridge performance when bidirectional dampers are incorporated.
... However, previous studies have carried out tests and finite element studies on columns, beams, joints, and other common components in steel structures under various extreme loads (such as earthquake, corrosion, fire, etc.), and little research has been conducted at the structural level [2][3][4][5][6][7][8][9][10]. When extreme loads such as earthquakes act on structures (such as long-span steel arch bridges), even if members such as columns and joints are not completely destroyed, the damage caused by excessive relative displacement between members (such as unseating due to damage of restrainers) might still seriously affect the service function of the bridge [11][12][13]. Therefore, from the perspective of the whole, the analysis at the structural level may be closer to the real situation. ...
In the present study, multiscale finite element (FE) models of half-through steel basket-handle arch bridges were established. The eigenvalue analyses were conducted to explore the dynamic characteristics of the arch bridges based on the FE models. In addition, a parametric analysis was carried out to investigate the impact of the inclination angle of the arch rib (0°, 4°, and 7°) on the longitudinal and transverse seismic performances of arch bridges. The results show that with the increase in inclination angle, the out-of-plane stiffness of half-through steel basket-handle arch bridges increases, resulting in the natural period of the structure becoming shorter from 3.09 s to 2.93 s. Adjusting the inclination angle appropriately has a beneficial impact on the overall seismic performance of the structures, affecting both displacement and internal forces, in which the most significant improvements include a 42.8% decrease in displacement and a 62.6% reduction in internal forces. Adjusting the inclination angle can cause the arch springing and transverse brace to undergo larger plastic deformation. It is advisable to judiciously enlarge the sectional dimensions and enhance the material strength of both the arch springing and the transverse bracing in seismic designs.
... Additionally, the effect of local tensile strains in the bearings can be effectively mitigated due to the single-side bonding. Previous studies have incorporated the seismic sliding behavior and resultant isolation effect of SSB bearings, both experimentally [22][23][24][25] and numerically [26][27][28][29]. However, the sliding of SSB bearings may cause excessive girder displacements during strong earthquakes, necessitating the application of restraints to control bearing sliding displacements [30,31]. ...
To enhance the seismic performance of highway bridges supported by laminated rubber bearings, this study proposes a novel hybrid placement of bonded and unbonded bearings. The typical analytical models of the hybrid bearing system are obtained and its critical design parameters are identified through theoretical analysis. A design procedure is then established to rapidly determine the design parameters for the hybrid bearing system according to specified design objectives. Nonlinear time history analyses are conducted to demonstrate the impact of the hybrid bearing system on the seismic responses of bridges. The analytical results indicate that the hybrid bearing system, when designed using the proposed procedure, can achieve the desired hysteretic behavior. The hybrid system combines the benefits of both bonded and unbonded bearings, effectively controlling maximum and residual bearing displacements without significantly increasing the seismic demand on bridge piers. The design parameters for the hybrid bearing system should be determined by carefully balancing the responses between the bearings and the piers.
... They have demonstrated a high capability for dissipating energy under dynamic loads. In most cases, dampers absorb energy as a result of material failure, yielding [20], or the movement of viscous liquid through orifices [21,22]. Viscous dampers are one type of damper that has demonstrated excellent performance under dynamic loads. ...
It's crucial to keep bridges safe and operational all the time. They may require immediate seismic retrofitting before or after an earthquake. A solution could be using the concepts of weakening and damping, which have not been widely used in bridge applications. The weakening is achieved by isolating piers with Elastomer Bearings (EBs), and viscous dampers are added for the damping part. Since a proper damping coefficient distribution and velocity exponent are required for the concept, the study investigated an optimal velocity exponent and presented a novel iterative-based design approach for viscous damper distributions. The results revealed that Sys1 (EBs + nonlinear viscous damper) and Sys2 (EBs + linear viscous damper) lowered the maximum bending moment of the most affected pier between 77% and 89%, and 82% and 90.5%, respectively when compared to the “pier fixed” system (i.e., the piers are fixed to the deck). For the maximum deck shear force, Sys1 increased the forces between 70% and 155%, whereas Sys2 increased the forces between 17% and 77%. In conclusion, Sys2 outperformed Sys1 by lowering the piers' bending moment and resulting in lower deck shear forces. Deck shear forces could also be decreased to a tolerable level by selecting a bearing with different mechanical properties (such as a lead rubber bearing).
... The experimental result highlighted that the transversal poundings at the shear keys can contribute to an increase in bending moment at the pier bottom. To reduce the adverse effect of transversal poundings on the highway bridge, a new type of steel damper was proposed by the authors [47,48] and was recommended to replace traditional shear keys. However, the shear keys used in highspeed railroad (HSR) bridges in China are different from those in highway bridges. ...
Shear keys bolted at the underside of bridge girders are expected to act as restrainers to prevent girder dislocation in the transversal direction when experiencing a strong earthquake. However, the impact forces generated at the restrainers will be transferred to adjacent structures and may cause damage to the bridge. Previous research on this topic was scarce as shear keys are usually regarded as secondary structures due to their relatively small dimensions compared to the main components, e.g., girders and piers. This study investigates the pounding effect on the transmission of seismic force in a simply-supported bridge with spherical steel bearings. Shake table tests are carried out on 1:6 scaled models with and without shear keys. To incorporate the effect of excitation characteristics, three ground motions with different peak accelerations are considered. The result indicates that in the absence of shear keys (i.e., no pounding), the bearings can partially isolate the girder from piers. Consequently, the table acceleration transferred to the girder is much smaller than to the pier top. In the case of installing shear keys, the seismic behavior of bearings would significantly influence the pounding occurrence and thus the subsequent bridge response. When involving poundings, the generated impact loads will dramatically increase the acceleration of the girder and the bending moment at the pier base compared to the counterpart without shear keys. Based on the experimental result, a numerical model is established and validated. The model is then used to determine a proper gap size between the participating impact components for obtaining a good overall bridge performance.
... The unbonded laminated rubber bearing (ULRB) supported highway bridges have been widely built in China [1][2][3]. They act as the lifeline infrastructure and play a key role in post-earthquake recovery, especially in densely populated urban areas. ...
Predicting the post-earthquake residual displacement of isolated bridges is crucial in deciding their operational and recovery strategies after a seismic event. This study proposes a probability-based approach to estimate the residual displacement of a trilinear hysteretic system representing the unbonded laminated rubber bearing (ULRB) supported highway bridge retrofitted with transverse steel dampers (TSDs), considering the uncertainty of structural parameters and the variability of ground motions. To this end, this study systematically derives the quasi-static residual displacement of a trilinear hysteretic system, and presents the statistical distribution model for the related structural parameters, especially for the pier height and the TSD model parameters. After that, the dynamic residual displacement property of the ULRB supported highway bridge retrofitted with TSDs is investigated considering the uncertainty of various parameters, including model parameters of TSD and ULRB, the mass of superstructure, the height of piers, as well as the ground motions with and without pulse. The maximum possible residual displacement of the trilinear hysteretic system is then related to its quasi-static residual displacement and peak displacement demand. Finally, an innovative probability-based approach is developed in this study to estimate the conditional probability of the dynamic residual displacement of the trilinear system exceeding a threshold at the given ground motion intensity, and this innovative approach is further validated by comparing it with the incremental dynamic analysis (IDA) method. Results show that the dynamic residual displacement of the TSD retrofitted ULRB supported highway bridge system is random, and the ratio between the dynamic residual displacement and the maximum possible residual displacement approximately satisfies a uniform distribution bounded by zero and one. The probability-based approach can obtain a close result with the IDA method and significantly reduce computational efforts. This research represents a first step toward developing a rapid post-earthquake assessment approach for seismically isolated bridges and the seismic design of these bridges considering the residual displacement.
... Extensive studies suggest that using seismic bearings and dampers leads to seismic retrofit of buildings and bridges (Xiang and Li 2016;Mansouri and Nazari 2017;Zhou and Tan 2018;Luo et al 2019;Kontoni and Farghaly 2019). Recently, studies on the effects of using seismic bearings and dampers indicated that these devices could reduce the seismic response of structures (Cho et al 2020;Hassan and Billah 2020;Cao et al 2020;Zheng et al 2020;Wei et al 2021;Xing et al 2021;Ristic et al 2021;Khedmatgozar Dolati et al 2021;Yuan et al 2021;Chen and Xiong 2022;Marnani et al 2022;Guo et al 2022). ...
This paper investigates the effects of earthquakes’ duration, intensity, and magnitude on the seismic response of reinforced concrete (RC) bridges retrofitted with seismic bearings, such as elastomeric bearings (EB), lead rubber bearings (LRB), and friction pendulum bearings (FPB). In order to investigate the effects of the seismic isolation, the condition of the deck with a rigid connection on the cap beams and abutments (i.e., without isolation) was investigated as the first model. The EB, LRB and FPB bearings are used between the superstructure and substructure of the studied bridge in the second, third and fourth models, respectively. First, the effects of using seismic bearings on the seismic retrofit of an RC bridge under the Tabas earthquake were investigated. The results of the nonlinear dynamic analysis showed that the use of seismic bearings leads to seismic retrofit of the studied bridge, and FPB and LRB had the best results among the studied isolation equipment, respectively. The same models were also studied subjected to the Landers and Loma Prieta earthquakes. The magnitude of the Landers and Tabas earthquakes is equal to 7.3 Richter, and the magnitude of the Loma Prieta earthquake is equal to 6.7 Richter. However, the duration and intensity of the Landers and Loma Prieta earthquakes are much larger than the Tabas earthquake. The Landers and Loma Prieta earthquakes caused instability in the isolated models due to their significant duration and intensity. This issue shows that using seismic bearings is very useful and practical for seismic retrofitting bridges subjected to far-fault earthquakes. According to most seismic codes, selecting earthquakes in far-region of faults is based on just magnitude criterion. However, this study indicates that there are two main factors in the features of far-fault earthquakes, including duration and intensity. Ignoring these factors in selecting earthquakes may lead to the instability of structures. Considering earthquakes’ duration, intensity, and magnitude are vital for selecting earthquakes in the far region of the fault.
... Nevertheless, it can be shown from the post-earthquake investigations of the 1995 Kobe earthquake that such restrainers cannot meet expectations in restraining displacement due to their poor deformation ability [10]. Concrete shear keys are restrainers constructed on abutments or piers, which mainly depend on self-stiffness to provide transverse support for superstructures of bridge [11][12][13][14][15]. However, this type of restrainer usually affects a bridge due to the sudden changes in stiffness when an earthquake occurs. ...
The steel ring restrainer (SRR) is a novel restrainer for bridges, which can prevent the unseating of bridges when an earthquake occurs. The traditional SRR is commonly made of mild steel, so it has the limitation of low strength and insufficient safety margin. In this paper, a new type of high-performance steel with negative Poisson’s ratio effect (NPR steel) is introduced for use in an SRR. Finite element (FE) models of SRRs are constructed, and the credibility of the FE model is validated based on previous experiments. Then, the FE models of SRRs under the mild steel, high-strength steel, and NPR steel are established, and the mechanical performance of SRRs fabricated of different steel grades is compared. The comparison results show that the macroscopic deformation processes of SRRs made of different steel grades during operation are similar, but their mechanical properties differ. Among them, the SRR made of NPR steel (SRR-NPR) has the advantage of high strength, excellent ductility and sufficient safety margin, so it can overcome the limitations of traditional SRRs. Subsequently, in order to further explore the mechanical behavior of SRR-NPR, several FE models of SRR-NPR are supplemented by changing the design parameters. The analytical results indicate that the trends in the influence of the design parameters on the mechanical properties of SRR-NPR are similar to those of traditional SRRs. However, the sensitivity of the mechanical properties of SRR-NPR to design parameters is higher than that of traditional SRRs. Finally, based on the results of numerical analyses, the problem that the conventional method of predicting the relationship between force and displacement of SRRs is inapplicable to SRR-NPR is overcome, and prediction formulas of SRRs that considers more factors are proposed and verified.
... The analytical model is developed based on the strut-and-tie models. Following the study by Megally et al. (2002) and Xiang and Li (2016), the lateral capacity of shea key, V y , is contributed by concrete, V c , and steel reinforcement, V s . Two parallel nonlinear springs in series with a gap element (see Figure 2) are assigned to describe the nonlinear behavior of the concrete, reinforcement, and gap of the shear keys. ...
... Two parallel nonlinear springs in series with a gap element (see Figure 2) are assigned to describe the nonlinear behavior of the concrete, reinforcement, and gap of the shear keys. To achieve this, bilinear and trilinear materials are properly defined to model the contributions of concrete and reinforcement (Xiang and Li, 2016). ...
The use of superelastic shape memory alloy (SMA) in reinforced concrete (RC) pier and restrainers between girder and pier/abutment has been proposed in an earlier study to improve the seismic performance of highway bridges. This paper aims at identifying the significant factors that affect the seismic response of such a novel bridge system. A sequential fractional factorial design method is performed to statistically evaluate the effects of six design factors (three geometry-related and three material-related) as well as their interactions. Additionally, a multi-criteria optimization technique is implemented to determine the most efficient combination of the design parameters for SMA RC piers and SMA restrainers. Results demonstrate that the geometry-related factors and their interactions have large effects (with a contribution greater than 91%) on the relative displacement between the girder and pier. The target residual drift of the pier, design target displacement of the restrainer, and their interaction are the three most significant factors (with contributions approximately 30%–68%) affecting the base shear of the pier. The residual drift of the pier is sensitive to the design target displacement of the restrainer, its interaction with the forward transformation stress of SMA, and material-related factors with regard to the energy dissipation of SMA.
... Given the imperative need to avoid superstructure unseating, numerous analytical and experimental studies have been carried out on devices that modify its response or prevent its collapse [15][16][17][18][19][20][21][22][23][24][25]. Saiidi et al. [15] carried out a parametric study of restrainer devices as an alternative to seismic retrofitting of bridges. ...
... Among studies related to transverse displacements, Xiang and Li [25] analytically and experimentally evaluated the seismic behavior of concrete shear keys, flexible steel dampers, and friction dampers as transverse displacement prevention devices. Although these devices reduce the seismic demand, the results showed that the seismic demands are lower for the friction damper and the flexible steel damper as compared to the shear keys. ...
... Introducing the kinetic energy from Equation (25) and the generalized forces from Equations (27) and (28), the equations of motion for the substructure and the superstructure result: Moreover, Equations (31) and (32) can be resumed in one matrix equation as follows: ...
Shear keys are elements in bridges designed to prevent or limit transverse unseating, rotation, and/or collapse of the superstructure responding to strong-intensity earthquake input ground motion, as well as to absorb breaking and various self equilibrating forces. During the 2010 Maule earthquake, Chile's highway infrastructure was seriously impacted. Shear key failures were endemic and did not function as intended. As a result, some bridges experienced partial or complete collapse. Even when the shear keys appeared to have worked, the superstructure exhibited large offsets, which required expensive repairs. An expensive retrofit of undamaged bridges was also carried out as a result of the inadequate response of the bridge infrastructure. This paper addresses the behavioral issues of bridges designed incorporating conventional shear keys and proposes an innovative self-centering concept that eliminates residual displacements in the superstructure. The self-centering shear key concept, as it will be termed here, makes use of the bridge self-weight as a restoring force to ensure self-centering. This concept proposal takes advantage of the kinematics of the bridge. The self-centering shear key concept was validated for a typical Chilean bridge via an extensive study that made use of nonlinear time history analyses. The results indicate that the increase in seismic demand on the substructure is small enough to maintain the bridge base structure in the elastic range while eliminating any residual displacements in the superstructure.
