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In this study, a procedure is developed to evaluate and improve the seismic performance of long-span suspension bridges based on the performance objectives under the fragility function framework. A common type of suspension bridge in China was utilized in the proposed procedure, considering its approach structures according to earthquake damage exp...
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Extended Abstract :
Today, a wide range of tools and software are available for nonlinear dynamic analysis as a comprehensive method for estimation of seismic demand in highway bridges. Generally, nonlinear structural analysis methods based on the structural mechanic and mathematical methods are using in the estimation of the structural vulnerabili...
Citations
... Out of three different anti-seismic methods (FVDs, friction dampers, shear link method), the FVD had the lowest base shear demands and had the most beneficial effects on the bridge model in the transverse direction (Vader & McDaniel, 2007). Analyses from both the Vincent Thomas Bridge and the Taoyuan Bridge commonly uphold the result that FVDs can limit earthquakeinduced displacements and damp forces at a satisfactory level (Ingham et al., 1997;Lu et al., 2020). ...
... Seismic isolators, according to analyses, can also reduce the stress put on bridges during earthquakes. The elastomeric isolator system of the Taoyuan Bridge was found to be able to lessen the demand on the bridge column (Lu et al., 2020). Similarly, the Shipshaw Cable-stayed Bridge (although not a suspension bridge,) had substantial decreases in deck acceleration, base moment, and shear force with seismic isolators compared to a model without (Javanmardi et al., 2017). ...
... Most research, including papers from Casciati andGuiliano (2009), Vader andMcDaniel (2007), Ingham et al. (1997), Lu et al. (2020), Raheem et al. (2011), andJavanmardi andGhaedi (2017), examined performance through nonlinear modeling analyses of simplified bridge forms or mock structures derived from existing bridges. Other research from Mokrani et al. (2017) and Meng et al. (2020) performed experimental labs to confirm findings from numerical analyses. ...
Suspension bridges are vital transportation infrastructures that support high traffic levels. It is of great importance for suspension bridges to remain operational following hazardous earthquake motions. Seismic devices preserve crucial bridge elements and aid in the control of ground motion response through energy dissipation and damping. This literature review introduces and evaluates the performance of widely-applied anti-seismic technologies such as tuned mass dampers, fluid viscous dampers, and seismic isolators in suspension bridge designs. The paper condenses and compares the results of analytical literature surrounding the effectiveness of seismic devices. Conclusions from current research indicate that the implementation of fluid viscous dampers is optimal for deck displacement damping in suspension bridges. Less effectiveness is found for seismic isolators and almost negligible success is found for tuned mass dampers under high seismic motions. The generalization of the results and the potential performance discrepancies due to spatial variability are noted.
... In theory, the distinction between the two frameworks involves the different ways of considering IM when building seismic demand models. In terms of implementation, the classical cloud approach requires that the engineering demand parameters (EDPs) calculated by nonlinear time history analysis (NTHA) meet normal distribution in logarithmic space, and keep a linear relationship with IM, which finally establishes an explicit relationship between IM and P f [1][2][3][4]. The IDA methodology does not explore the explicit relationship between EDP and IM, but directly calculates the damage probability under specified ground motion intensity. ...
A R T I C L E I N F O Keywords: Small-and medium-span girder bridges Double-column piers Cox hazard model Survival analysis Fragility A B S T R A C T Fragility analyses have undoubtedly been critical steps in the seismic risk assessment of highway bridges, and even in transportation networks. In view of the shortcomings of the previous fragility analysis methods, this paper discusses the application of survival analysis based on the Cox hazard model in the establishment of bridge pier seismic fragility. In the IDA framework, the ground motion intensity and censored value (damage state) are taken as dependent variables, and the pier attributes are used as covariates to generate fragility curves. Next, the uniform design experiment is used to generate the attribute data set training model of the pier samples. It can be observed that compared with the traditional strip analysis method, the proposed procedure can provide accurate estimation of the fragility curves, and the fragility curves established by the traditional method are in fact the fragility curve corresponding to the pier average sample. In addition, the primary survival analysis of the pier samples with average value and the hazard ratio provided by the Cox model can be used to quickly analyze the impact of significant factors on the fragility curves and estimate the seismic loss. The pier height, reinforcement ratio and reinforcement strength may be the dominant factors affecting the pier seismic loss in highway bridges.
... In the previous sections, the sliding characteristics of LRBs with different frictional surfaces have shown that the three-fold mechanical constitutive model is considered to be a reasonable model for accurately emulating the sliding characteristics of the LRBs. Two parallel non-linear spring elements were employed to simulate the behavior of LRBs under earthquake load in OpenSEES [15,36]. One of the spring elements was modelled by Steel01 material, which mainly simulates the frictional force requirements when LRBs are under sliding friction. ...
Unbonded LRBs (laminated rubber bearings) are commonly applied in small-to-medium-span bridges in China. The frictional sliding characteristics of LRBs have a vital influence on the seismic response of the bridge. Nine square LRBs were subjected to the quasi-static displacement loading test in this paper, and the differences in sliding characteristics of LRBs at the interface of steel and concrete test pad were investigated. The variation of the friction coefficient during sliding was then analyzed. Based on the experimental data, a three-fold mechanical constitutive model of LRBs that considers the breakaway-sliding friction characteristics is established. Further, the bridge seismic demands in longitudinal directions with different friction interfaces are compared by nonlinear dynamic analysis on a typical LRB-supported concrete bridge. The results show the causalities of the displacements and decreases of the friction coefficient of the LRB. The breakaway coefficient of friction of the concrete surface was generally greater than that of the steel in the pre-sliding stage, while the sliding coefficient of friction of the steel interface in the post-sliding stage was greater than that of the concrete. Moreover, the proposed three-fold constitutive model is able to simulate the frictional sliding behavior of LRBs accurately. Lastly, the seismic design of small-to-medium-span bridges should take into account the breakaway-sliding friction effect of the LRBs and the preference for steel as friction pads for LRBs is recommended.
... For the study of the seismic vulnerability of bridges, most of the research studies have been conducted on completed bridges [3,4]. To study the seismic fragility of long-span suspension bridges, Lu et al. [5] applied the probabilistic seismic demand models (PSDMs) method and improved a design based on fragility. Wu et al. [6] applied the incremental dynamic analysis (IDA) method and obtained the seismic capacity residual ratio of a structure. ...
To evaluate the vulnerability of bridges at various construction stages under the action of strong earthquakes, the incremental dynamic analysis (IDA) method is applied, and the vulnerabilities of a continuous girder case study bridge with the cast-in-place cantilever construction method, which owns five main construction stages, are evaluated and compared. The results show the following: With the increase in the peak ground acceleration (PGA), the vulnerabilities of bridges at different construction stages all increase. The fragility and vulnerability are mainly determined by the structural mechanical system condition and the mode shapes but not the modal frequency. For the working condition of seismic PGA of 0.4 g, (1) the bridge at the substructure construction stage may only experience slight or moderate damage with the exceedance probability of 8% to 5% and the mean loss ratio being only about 5%; (2) the vulnerabilities of bridges at the middle cantilever construction stage and the long cantilever construction stage are similar, the collapse damage exceedance probability is about 80%, and the mean loss ratio is about 65%; and (3) the vulnerabilities of bridges at the middle span closure construction stage and the bridge completion construction stage are nearly the same, the collapse damage exceedance probability is about 98%, and the mean loss ratio can reach 80%. The research results explore a new method for evaluating the vulnerability of bridges at different construction stages, which can provide suggestions for seismic damage defense and seismic insurance risk evaluation.
Double-deck curved bridges can overcome the limitation of space, connecting areas with complex terrains to form a traffic network. However, they have many vulnerable parts and weak seismic performance, which can easily paralyze the traffic network. Seismic fragility can quantify the seismic performance of double-deck curved bridges from the perspective of probability, which provides a reference for the seismic design and evaluation of bridges. Therefore, in this study, the excitation angle of the ground motion was considered a random variable with a uniform distribution to consider its randomness. In addition, based on the random forest algorithm and partial dependence plots, an analysis framework of the multiparameter fragility model of a double-deck curved bridge was established, and an efficient vector model was constructed in the analysis framework to predict the demand and capacity of the double-deck pier. The analysis results indicated that [0, 0.06π] is the most sensitive range of fragility of double-deck curved bridges to seismic excitation angle θ; if θ < 1.56π, the bridge is a typical ductile seismic system owing to the energy dissipation part of the bridge being at the pier; if θ > 1.56π, the damage of the upper constraint system precedes the yielding of the pier, which has a particular role in seismic reduction and isolation; among all possible seismic excitation angles, the unseating risk of the upper beam is higher than that of the lower beam. The spacing between the upper beam and its limit device can be appropriately increased or double-layer limit devices can be set to enhance the seismic performance of double-deck structures.
Buckling-restrained braces (BRBs) are widely used to improve the seismic performance of buildings. This paper aims to introduce BRBs to suspension bridges and assess the seismic performance of bridges with BRBs. Taking the Dadu River Bridge as a case study, an FEA model of the bridge is established, and different seismic measures (BRBs between the deck and the tower, BRBs at the middle of the span to replace the inclined suspenders to connect the deck and the main cables, fluid viscous dampers (FVDs) between the deck and the tower, the combination of BRBs to replace the inclined suspenders as well as FVDs between the deck and the tower) are applied to the suspension bridge. The influence of the parameters of BRBs on the seismic response of the suspension bridge is studied, and the performance of the bridge with BRBs is compared with that of the bridge with FVDs. The results indicate that the use of BRBs in place of the inclined suspenders is beneficial to reduce the displacement of the deck and limit the shear force and bending moment of the tower. The seismic performance of the suspension bridge with BRBs and FVDs is better than that of the bridge with BRBs or FVDs. Therefore, the application of BRBs is a feasible method to improve the seismic performance of the suspension bridge.
