地震作用下库区拱桥的动水响应研究

发布时间：2018-07-06 17:15

本文选题：库区拱桥 + 拱圈淹没深度　；参考：《昆明理工大学》2017年硕士论文

【摘要】：位于高烈度地区的库区上承式拱桥,地震作用时因受到动水压力作用,其地震响应与普通上承式拱桥(无水时)差异较大。工程中,为了减小拱圈跨径或降低工程投资,常以增加拱圈淹没深度为代价,而淹没深度是影响动水压力的主要因素。库区拱桥的地震响应与拱圈淹没深度以及激励方向密切相关,目前这方面的研究较少。本文以永春河大桥为依托,对不同拱圈淹没深度下的库区拱桥作动力特性分析,研究动水压力对拱圈内力、位移的影响规律,并分析库区拱桥的最不利地震响应。本文主要研究内容及结论如下:(1)阐述和对比了常用的动水压力计算理论,并在考虑内域水(拱箱内水体)的影响下,推导出拱圈动水压力计算式。概述有限元和地震时程分析理论,推导得库区拱桥自振特性的求解公式。本文选用Morison方程和欧洲规范计算动水压力,并比较两者的差异。(2)分析不同拱圈淹没深度下,动水压力对拱桥自振特性的影响。分析得出,拱桥自振频率与拱圈淹没深度成反比;当淹没深度超过5f/8(f是计算矢高)后,结构频率降低速率加快,且出现振型对调的情况;动水压力主要影响低阶振型,而对6阶以上振型影响较小。(3)对不同淹没深度下的拱桥作地震激励分析,以研究动水压力对拱圈内力及位移的影响规律。分析得出,当淹没深度小于5f/8时,动水压力对拱圈内力、位移的影响较小;超过5f/8后,欧洲规范计算结果偏小且不合理,应采用Morison方程计算动水压力;对于高烈度地区的深水拱桥,建议拱圈淹没深度小于5f/8。(4)综合分析了地震激励方向、拱圈淹没深度对库区拱桥地震响应的影响,并得到拱圈内力、位移的最不利地震响应规律。分析表明,0°、45°和90°(与拱桥纵轴线的逆时针夹角)均有可能是最不利激励方向,主要依拱圈内力和位移类型而定;拱圈横桥向剪力Fy、弯矩Mz、扭矩和拱顶横桥向位移DY的最不利激励方向为45°,进行设计时可按0°考虑,但需将设计值提高约40%计算。(5)对于高烈度地区的库区拱桥,当淹没深度超过5f/8后,应加强拱脚段的轴心抗压、竖向抗剪以及抗扭能力;加强4L/16截面处的抗扭能力(L为净跨径);加强2L/16、5L/16截面处的横桥向抗弯能力;加强拱顶处的竖向抗剪及抗变形能力。
[Abstract]:The seismic response of the upper bearing arch bridge in the reservoir area in high intensity area is different from that of the ordinary arch bridge (when there is no water) due to the action of dynamic water pressure. In order to reduce the span of arch ring or reduce the project investment, increasing the submerged depth of the arch ring is often the cost, and the submerged depth is the main factor affecting the dynamic water pressure. The seismic response of arch bridges in the reservoir area is closely related to the depth of arch submergence and the direction of excitation. Based on the Yongchun River Bridge, this paper analyzes the dynamic characteristics of the arch bridges with different submergence depths in the reservoir area, studies the influence of the hydrodynamic pressure on the internal forces and displacements of the arch rings, and analyzes the most unfavorable seismic response of the arch bridges in the reservoir area. The main contents and conclusions of this paper are as follows: (1) the commonly used calculation theory of dynamic water pressure is expounded and compared, and the calculation formula of dynamic water pressure of arch ring is deduced considering the influence of inner region water (water body in arch box). The finite element method and seismic time history analysis theory are summarized, and the formulas for solving the natural vibration characteristics of arch bridges in reservoir area are derived. In this paper, Morison equation and European Code are used to calculate the dynamic water pressure, and the difference between them is compared. (2) the influence of dynamic water pressure on the natural vibration characteristics of arch bridge is analyzed under different submergence depth of arch ring. The analysis shows that the natural vibration frequency of arch bridge is inversely proportional to the submerged depth of arch ring; when the submergence depth exceeds 5f/8 (f is the calculated vector height), the frequency reduction rate of the structure is accelerated, and the vibration mode is adjusted, and the dynamic water pressure mainly affects the low order vibration mode. In order to study the influence of hydrodynamic pressure on the internal force and displacement of arch ring, the seismic excitation analysis of arch bridge with different submergence depth is carried out to study the influence of dynamic hydrodynamic pressure on the internal force and displacement of arch ring. The results show that when the submerged depth is less than 5f/ 8, the influence of hydrodynamic pressure on the internal force and displacement of the arch ring is small, and when the calculation results are small and unreasonable after 5f/8, the dynamic hydrodynamic pressure should be calculated by using Morison equation. For deep water arch bridges in high intensity area, it is suggested that the submergence depth of arch circle be less than 5 f / 8. (4) the direction of earthquake excitation and the influence of submergence depth of arch circle on seismic response of arch bridge in reservoir area are comprehensively analyzed, and the most unfavorable seismic response law of arch ring internal force and displacement is obtained. The analysis shows that both 0 掳and 90 掳(angle of counterclockwise angle to the longitudinal axis of the arch bridge) are probably the most unfavorable direction of excitation, which is mainly determined by the type of internal force and displacement of the arch ring. The most unfavorable excitation direction of shear force FY, moment Mz, torque and displacement DY of arch ring transverse bridge is 45 掳, which can be considered as 0 掳in design, but the design value should be increased about 40%. (5) for reservoir arch bridge in high intensity area, When the submergence depth exceeds 5f/8, the axial compression, vertical shear and torsion resistance of the arch should be strengthened, the torsion resistance at the section of 4L / 16 (L is the net span), the flexural capacity of the transverse bridge at the section of 2L / 165L / 16 should be strengthened, and the bending resistance of the transverse bridge at the section of 2L / 165L / 16 should be strengthened. Strengthen the vertical shear and deformation resistance of the vault.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U448.22;U442.55

【参考文献】