城市轨道交通振动下西安鼓楼动力响应分析

Analysis of the Dynamic Response for Xi’an Drum-Tower under the Vibration of Urban Rail Transit

为评估城市轨道交通振动对古建筑木结构的影响,本文以西安鼓楼为研究对象,综合运用现场振动测试和有限元数值模拟的方法,研究了西安鼓楼的动力特性以及地铁六号线不同运行模式下西安鼓楼的动力响应规律,并依据国家相关规范对其振动性能进行预评估.结果表明:目前状态下,西安鼓楼木结构东西方向一阶频率为1.2081Hz,南北方向一阶频率为1.5572Hz;西安鼓楼整体结构的低阶自振频率和振型与木结构较为接近,四阶以上的自振频率和振型与高台基更为接近;地铁六号线以不同模式运行时,高台基和木结构对于加速度响应和速度响应普遍具有放大效应;地铁运行引起的振动不仅与车速有关,还与地铁振源的频率特性有关;当地铁六号线以单线40km/h运行时,西安鼓楼顶层柱顶水平速度响应达到最大值0.1719mm/s,低于规范规定的容许振动速度.此研究结果可为西安地铁六号线的施工及西安鼓楼延寿保护提供理论依据.

In order to evaluate the effect of the vibration of urban rail transit on the wooden structure of ancient architecture, Xi’an Drum-Tower was chosen as the research object in this article.By combining on-site vibration test with finite element numerical simulation, the dynamic characteristics of Xi’an Drum-Tower and its dynamic response law under the operation of Metro Line 6 were researched, the result of which was then used topre-evaluate the vibration performance of Xi’an Drum-Tower according to relevant national norms.It shows that the current first-order frequency in the east-west direction and south-north direction for the wooden structure of Xi’an Drum-Tower is 1.2081 Hz and 1.5572 Hz respectively.Moreover, the low-order natural vibration frequency and mode for the overall structure of Xi’an Drum-Tower are closer to that of the wooden structure, while the above-fourth-order natural vibration frequency and mode are closer to that of the high stylobate.When Metro line 6 is operated under different modes, both the high stylobate and the wooden structure generally have an amplification effects on the acceleration and velocity response.The vibration induced by metro operating is not only related to the metro speed, but also related to the frequency characteristics of the metro vibration source.When Metro Line 6 runs at 40 km/h under single-line mode, the horizontal velocity response at the top of the pillar on the attic of Xi’an Drum-Tower reaches the maximum of 0.1719 mm/s, which is lower than the permissible vibration velocity in relevant national norms.These results can provide a theoretical basis for the construction of Xi’an Metro Line 6 and the life extension and protection of Xi’an Drum-Tower.