高墩自复位隔震机理与设计方法研究

Bridges supported on tall piers with pile foundations are widely constructed in the western areas of China with high earthquake intensities. However they are unfavorable earthquake resistance systems. The damages of tall piers from earthquake action impose great threats on the politics, economy and national defense. Domestic and foreign seismic codes do not apply to the seismic design of tall piers. The multiple plastic hinge zones in the pier combined with the huge earthquake action of the pile cap base make it difficult to be designed according to the traditional method. The deformation capacity and self-centering are very limited for common isolation bearing. The expensive viscous damper has directionality, and its stroke is also limited. Based on the principle of avoiding seismic damage, with the separate of the piers and pile foundation at the pile cap for tall piers with pile foundations can utilize the vertical loads of the structural system like dead load to counteract the wind load, braking force of train and the frequent earthquake action under the normal use and so as to make sure the serviceability of the structures. While subjected to the strong earthquake, the bridges can isolate the earthquake action by the up-lift of the tall piers, which can avoid the development of plastic hinge region in the piers，and the tall piers can reset by gravity after earthquake. Since the self-centering pier has an explicit bending moment at the bottom, the seismic damage can be easily avoided for both the pier and pile foundations by the principle of capability design. The self-centering device for tall piers with pile foundations is proposed in the issues, and its analysis model will be established. Relationship between bending moment of the pier base and the key parameters of seismic isolation device will be defined. Function between pier top displacement and the key parameters of restrainer will be discussed. The effect of input ground motions on the rocking response of tall pier - pile foundations will be brought to light. Mechanism of the tall pier - pile foundations will be clarified. Seismic design methods for tall pier with self-centering device will be established.

高墩桥梁在我国西部高烈度地震区被广泛应用,却是抗震不利的结构体系。高墩地震破坏对政治、经济及国防有重大影响。国内外的抗震规范均不适用于高墩。墩中多个塑性铰区及承台底巨大地震作用使得其按传统方法抗震设计存在困难。常用的支座减、隔震装置变形及自复位能力有限，粘滞阻尼器具有方向性、冲程有限且价格昂贵。桩基础高墩自复位隔震基于避免地震损伤的设计理念,通过桥墩与桩基础在承台处分离，充分利用自重等竖向荷载平衡水平荷载以满足正常使用，强震时利用桥墩的提离进行摇摆隔震，震后靠自重实现自复位。自复位隔震高墩的墩底提离弯矩明确，通过能力设计很容易保证桥墩及其桩基础免受地震损伤。本课题提出桩基础高墩的自复位隔震装置,建立其分析模型，明确墩底弯矩与隔震装置关键参数的关系、墩顶位移随限位装置关键参数变化的规律,揭示地震动输入对高墩摇摆反应的影响，阐明桩基础高墩的自复位隔震机理,建立桩基础高墩自复位隔震的设计方法。