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- 2018
考虑SSI的整体式钢桥抗震性能参数分析
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Abstract:
利用SAP2000建立了某整体式钢桥的三维有限元模型,采用非线性弹簧单元和阻尼单元模拟地震作用下桥台-土和桩-土之间的相互作用,分析了桥梁的模态、非线性时程与相应的参数,研究了考虑土-结构非线性相互作用的整体式钢桥动力特性和抗震性能,以及整体式桥台系统的主要设计参数对此类桥梁动力特性和抗震性能的影响。研究结果表明:压实台后填土、增加桥台高厚比、增加桩周土刚度将使桥梁结构纵向主频增加约6.5%~16.0%,而H型钢桩的朝向影响仅为1.6%左右; 结构地震响应随着桥台高厚比增加而明显降低,桥台高厚比为1.44时,桩顶截面处于塑性阶段,而高厚比增大到3.15和3.85后,桩保持弹性状态; 随着台后土密实度的减小,结构的地震响应明显增大,增幅大都在40%以上; 桩的朝向由绕强轴弯曲调整为绕弱轴弯曲时,桩的最大弯矩减小,但弯曲应力增大,材料由弹性进入塑性阶段; 随着桩周土刚度增大,桥梁位移响应明显减小,桩顶、台顶最大位移及墩底弯矩减小50%左右,但是桩顶弯矩增大40%以上,桩的朝向对此几乎无影响; 在满足设计要求及合理范围内,建议采用高厚比较大与柔性较高的桥台,并压实台后填土以减小整体桥结构的地震响应,桥台基础采用H型钢桩时,建议将其朝向调整为绕强轴弯曲以减小桩、桥台和墩柱的最大弯曲应力与位移。
A 3D finite element model of integral abutment steel bridge was established by the SAP2000 software, the nonlinear spring elements and damping elements were used to simulate the soil reactions behind the abutment and around the piles under the earthquake action, and the mode, nonlinear time history and relevant parameters of the bridge were analyzed, In addition, the dynamic and seismic behaviors of integral abutment steel bridge considering the nonlinear soil-structure interaction, as well as the influence of the main design parameters of integrated abutment system on the behaviors were studied. Research result indicates that compacting the abutment backfill, increasing the abutment height-to-thickness ratio, and increasing the foundation stiffness will increase the dominant longitudinal frequency of the bridge structure by about 6.5%-16.0%, while H pile orientation has a minimal influence of about 1.6%. The structural seismic response significantly reduces as the abutment height-thickness ratio increases. When the abutment height-to-thickness ratio is 1.44, the top of the pile enters the plastic stage. When the height-to-thickness ratio increases to 3.15 and 3.85, the pile remains elastic. When the compactness of the abutment backfill decreases, the seismic response of the structure increases significantly, and the increment is mostly above 40%. When the orientation of the pile is adjusted from bending about the strong axis to bending about the weak axis, the maximum bending moment of the pile decreases, but the bending stress increases, and the material enters the plastic stage from the elastic stage. As the soil stiffness around the pile increases, the displacement response of the bridge decreases significantly. The maximum displacements at the top of the pile and abutment, as well as the bending moment at the pier bottom decrease by about 50%. However, the bending moment at the pile top increases by more than 40%, and the orientation of the pile has almost no effect on the displacement responses.