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The effects of seawater and site conditions on the seismic response of the isolated continuous girder bridge are evaluated in this study. The seawater-muddy soil-isolated bridge coupling model is built in the dynamic analysis software ADINA, and the external seismic wave input is realized by the seismic wave motion analysis program. The influences...
Citations
... Seismic fragility analysis needs to select a sufficient number of seismic waves to account for the uncertainty of ground motion [27,28]. Based on the seismic fragility analysis of structures with the IDA method, selecting 10 to 20 ground motion records can achieve a certain accuracy [29]. ...
In order to accurately predict the seismic fragility of an aqueduct system, the General Product of Conditional Marginal (G-PCM) method was applied to the seismic fragility analysis of the aqueduct structural system, consisting of interrelated components such as the aqueduct body, pier, and support. First, a finite element dynamic analysis model of a three-span aqueduct with an equidistant simply-supported beam was established, based on the OpenSees platform. The uncertainties of structure, ground motion, and structural capacity were considered, and then the incremental dynamic analysis (IDA) method was used to calculate the seismic fragility of the three individual components, such as the aqueduct pier, the plate rubber bearing at the cap beam, and the PTFE sliding plate bearing at the aqueduct platform. Subsequently, seismic fragility curves of the aqueduct system were established using the G-PCM method and were compared with the traditional second-order bound method. The results showed that the two bearings of the aqueduct are more likely to be damaged than the pier; the failure probability of the aqueduct system is higher than that of any single component; and the seismic fragility curves of the aqueduct system acquired via the G-PCM method were all within the range of the failure probability obtained by the second-order bound method and had a better accuracy, which is suitable for the seismic fragility analysis of multi-failure mode aqueduct systems.
... The liquefaction of the foundation sand caused by the earthquake will make the foundation of the structure lose its bearing capacity and directly endanger the safety of the building. The state of saturated loose sand will change rapidly under the action of ground motion load and lose its original shear strength and bearing capacity, resulting in the destruction of ground and aboveground buildings, which is the so-called liquefaction phenomenon [3]. For many important structures, such as high-rise buildings, bridges, and nuclear power facilities, the seismic design of pile-soil structure system is a very important part. ...
To study the influence of the nonlinear connection of pile and soil on the dynamic response characteristics of the pile foundation, this article proposes to study the dynamic response of the bridge pile foundation to the slope by combining the centrifugal shaking table test and OPENSEES open source finite element program. This article introduces the pressure-dependent multiyield surface model based on confining pressure. Through the inverse calculation of the similarity ratio of the centrifuge model test, the OPENSEES two-dimensional nonlinear finite element model of the pile group in the slope section can be established. The centrifuge shaking table test is to input the preset seismic wave horizontally at the bottom of the model box. The form of seismic wave is El Centro wave verification of two-dimensional finite element model of the pile group in slope section under earthquake. The reliability of the model is verified by comparing the test and calculated values of dynamic response (residual horizontal displacement and final bending moment) of the pile body under five different peak acceleration seismic wave loading conditions. In the dynamic response experiment of slope pile foundation, in the embedded part below the bedrock surface, the residual horizontal displacement of each pile body is zero. Constrained by the cap beam and tie beam, the displacement of the free section of the pile group at these two positions is basically the same. Through comprehensive analysis, the displacement of P1 and P2 piles is basically the same. The calculated value of the final bending moment of P1 and P2 piles shows the same change trend as the test value, and the test value is slightly larger than the calculated value. The relative errors of the maximum final bending moment of P1 pile under each loading condition are 7.4, 7.8, 12.6, 3.9, and 9.6%, respectively, and the relative errors of P2 pile are 4.6, 3.6, 12.5, 13.6, and 11.5%, respectively. The analysis relative error is caused by the elastic element used in the calculation of the pile body, which is different from the mechanical behavior of the simulated pile body material in the test. Dynamic response of slope site according to the existing centrifuge test results can be seen that the deformation at the slope shoulder of slope site is the most obvious under the earthquake. The inclined interface of soft and hard rock and soil layer will aggravate the dynamic response of the overburden layer on the slope, weakening its ability of seismic energy consumption.
... Spyrakos et al. [21] analyzed the dynamic response of soil-structure-water interaction of the tower structure under horizontal earthquake action. Note that, for the bridge engineering, in the seismic analysis and design of some sea-crossing bridges, the seabed-pile-seawater interaction is not considered, while the method of directly inputting seabed ground motion or even land ground motion at the bottom of the fixed bridge foundation is adopted [22][23][24][25][26]. Based on Automatic Dynamic Incremental Nonlinear Analysis (ADINA [1]) and self-developed free site wave analysis program, Chen et al. [27,28] established a refined seismic response analysis model considering the coupling effect between seawater layer, seabed overburden, and sea-crossing cable-stayed bridge. ...
To consider the multiple interactions between offshore sites and sea-crossing bridges under seismic actions, a seabed–pile–seawater–bridge interaction model is established by the ADINA software [1]. This study uses seismic fluctuation analysis as an input to bedrock ground motion. It reflects the influence of submarine sites and seawater layers on ground motion characteristics through the fluid-solid coupling of seawater to the seabed. It was found that the whole bridge piers considering the coupling effect are in an elastic state. The yielding of the isolated bearings occurs. Also, the seismic response of the bridge structure under the seabed-pile-seawater-bridge interaction is significantly higher than those under the direct input of the ground motions from the fixed basement assumption. In addition, when the pile cap is above the seabed, the average seismic response of the bridge structure is 1.2–1.3 times the response when the pile cap is below the seabed. Therefore, the seismic design of marine structures should take full account of the influence of the submarine site and the seawater layer. Otherwise, it will result in greater seismic risks for marine structures such as sea-crossing bridges. In addition, this study also suggests the influence of the pile cap location on the seismic response of the bridge.
... Earthquakes are a critical reason for structural damage and collapse, and the structural responses under seismic loads are complex and diverse (Li et al., 2016;Xie and Qu, 2016;Chen et al., 2021a;Chen et al., 2021b). In the Northridge earthquake in the United States in 1994 and the Hanshin Awaji earthquake in Japan in 1995, many brittle fractures occurred in the beam-to-column connections of traditional steel frames, which seriously threatened the overall threat stability of the structure (Li et al., 1998). ...
To avoid brittle fracture and plastic yielding of steel beam-to-column connections under earthquakes, a new beam-to-column connection of steel structures with all-steel buckling restrained braces (BRBs) is proposed. The all-steel BRB is connected to the steel beam and column members through pins to form a new connection system. Taking the T-shaped beam-to-column connection steel structure as the research object, two structural types with an all-steel BRB installed on one side (S-type) and two sides (D-type) are considered. Theoretical equations of the connection system’s initial stiffness and yield load are derived through the mechanical models. The yield load, main strain distribution, energy dissipation, and stiffness of the connection system are investigated through quasi-static tests to verify the connection system’s seismic performance. The tests revealed that the proposed new connection system is capable of achieving a stable hysteresis behavior. At the end of loading, the beam and column members are not damaged, and the plastic deformation is concentrated in the plastic energy dissipating replaceable BRB, and the beam and column basically remain elastic. The proposed equations approximately estimated the load response of the proposed connection system. The results show that the damage mode of this new connection system under seismic loading is BRB yielding, with an elastic response from the beam-column members.
This paper studies the effect of seawater depth on offshore earthquake motion characteristics and seismic response of bridges. By analyzing the offshore seismic data recorded by the K-NET during 2006-2021. The horizontal amplification coefficient spectrum and V/H spectral ratio of offshore ground motions were compared for various offshore stations at different seawater depths. Moreover, a numerical model simulating the propagation process of seismic waves in the seabed was developed to investigate the effects of seawater depth and site conditions on offshore ground motions. Finally, a site-seawater-pile foundation-cable-stayed bridge coupling model was created to study the influence of seawater depth on the seismic responses of sea-crossing cable-stayed bridges. The results reveal that the vertical response spectrum of offshore ground motion in deeper seawater is lower for periods longer than 0.3 s. The numerical models reveal that seawater has a suppression effect on the P wave near the resonance frequency of the seawater layer. Due to the hydrodynamic effect, the longitudinal bridge seismic response is significantly amplified. The amplification effect becomes more obvious with an increase in water depth. Therefore, it is important to consider the influence of the seawater layer in the seismic design of sea-crossing bridges.
