混凝土桩与H型钢桩支撑的整体桥抗震性能研究

Study on the seismic performance of Integral Bridge Supported by Reinforcement Concrete and H-shaped Steel Piles

整体桥取消了全桥伸缩缝与伸缩装置,使其具有较好的整体性、行车舒适性与养护维修费用低等优点,深受国内外桥梁设计者的喜爱。国外整体桥多采用H型钢桩为主,然而,我国主要以混凝土桩为主,两者在受力方面存在较大差异。目前,对于整体桥在抗震性能方面的研究还不够深入,缺乏完善的抗震设计方法,对整体桥的推广与应用产生了较大影响。文中将依托某座整体桥,建立其全桥杆系有限元模型,模型中分别在其柔性桥台下设置混凝土圆形桩和矩形桩与H型钢桩,考虑E1、E2地震作用,对采用三种桩基支撑的整体桥上、下部结构的地震响应进行研究。研究结果显示:采用不同类型桩基对整体桥自振模态的影响较大,但对结构频率的影响较小,频率最大误差约为5.7%;在地震荷载作用下,H型钢桩支撑的整体桥在梁端会出现较大的竖向位移,易引起主梁与桥台固结处较大的拉应力,对主梁和桥台的受力不利;整体桥采用矩形桩可有效降低主梁的位移地震响应,但采用不同类型桩基础对其主梁内力地震响应的影响不大。其次,采用不同类型桩基对整体桥下部结构位移的地震响应存在较大差异,整体桥的桩基础变形普遍较小,主要依靠柔性桥台的变形来消耗地震能量;在强震作用下,整体桥的桩基础会承受较大的地震荷载,建议采用H型钢桩更好,其强度高,延性好,可很好地抵抗较大的地震荷载。混凝土桩基承受的地震荷载明显较H型钢桩大,尤其在大震区使用应采取有效措施防止混凝土桩基发生严重的混凝土破碎甚至剪切破坏。研究结果可为整体桥的抗震设计及相关规范制定提供参考。

The expansion joint and expansion device are eliminated in the integral abutment jointless bridge(IAJB).It has the advantages of favorable integrity,driving comfort and low maintenance cost,which is deeply loved by many bridge designers in the world.H-shaped steel pile is widely used in IAJB in the West,while the concrete pile is mainly adopted in China.A large difference in stress can be found in IAJB supported by concrete pile and H-shaped steel pile.At present,the research on the seismic performance of IAJB is superficial,and lack of a perfect seismic design method,which has a large impact on the promotion and application of IAJB.Based on a IAJB,its finite element model is established,in which the concrete circular pile,concrete rectangular pile and H-shaped steel pile are respectively set under the flexible abutment.Considering the E1 and E2 seismic loads,the paper studied the seismic responses of substructure and superstructure in IAJB supported by three types of piles.The results show that different types of pile foundation have great influence on the natural vibration mode of IAJB,but little influence on the structural frequency,and the maximum error of frequency is about 5.7%.Under the earthquake load,a large vertical displacement would occur at the beam end of IAJB supported by H-shaped steel pile,which can easily cause a large tensile stress at the fixed connection of girder and abutment.This is unfavorable to the stress of girder and abutment.The displacement seismic response of the girder can be effectively reduced in IAJB supported by rectangular pile,but the influence of different types of pile foundations on the internal force seismic response of the girder is not significant.Secondly,the displacement seismic responses of substructure in IAJB supported by different types of pile foundations are quite different.The deformation of pile foundation of IAJB is generally small,which mainly depends on the deformation of the flexible abutment to consume the seismic energy.Under the strong earthquake,the pile foundation of IAJB will bear a large earthquake load.It is recommended to use H-shaped steel pile to support the IAJB.It has high strength and good ductility and can well resist the large earthquake load.The seismic load of concrete pile foundation is obviously larger than that of H-shaped steel pile,especially in the large earthquake area,effective measures should be taken to prevent serious concrete crushing and even shear failure of concrete pile foundation.The results of this research in this paper can be used as a reference and guidance for the seismic design of IAJB and the formulation of relevant codes.