Study to Clarify The Mechanism of Uniquely Large Horizontal Bridge Response Located in The Wake of aHill

本研究旨在阐明在孤立山丘尾迹中观察到的桥梁模型的独特大水平响应机制。桥和山的模型被简化为一个悬臂和一个锥体。改变桥梁模型在山体尾迹中的位置和水平倾斜角度，并测量其响应。山的直径为4.5H，以H为高度。悬臂模型的长度为H，位于0.123H的高度。当模型位于离山中心约3.3H背风处时，水平响应变大。当风偏角为40度时，悬挑模型的响应也变大。反应的峰度有时达到4到4.5。通过一系列流动可视化实验，提出了轴角为40 ~ 50度的锥形涡的形成，并认为这些涡可能是产生较大水平响应的原因。然后同时测量响应和脉动风速，并根据大响应的发生情况进行条件采样，明确引起大响应的脉动风速特征。这是一些波动风速作用在倾斜锋线约40度的桥模型上引起较大响应的情况，这被认为与流动可视化实验中提出的涡结构相对应。另一方面，也有一些情况没有观察到这些波动的风速特征，或者实验结果的再现不好。考虑到流动条件等因素的敏感影响，目前正在寻找原因。采用同步测压实验，测量了气动力特性。

This study was conducted to clarify the mechanism of uniquely large horizontal response observed with a bridge model located in the wake of an isolated hill.The bridge and hill models were simplified as a cantilever and a cone. The location of the bridge model in the wake of the hill and horizontal skew angle were varied and responses were measured. The diameter of the hill was 4.5H, taking H as the height. The length of the cantilever model was H and it was located at height of 0.123H. The horizontal response became large when the model when the model was located around 3.3H leeward from the hill center. Also the response became large when the cantilever model had wind skew angle of 40 degrees. The kurtosis of the response sometimes reached to 4 to 4.5. With a series of flow visualization experiment, the formation of conical vortices that has the axis with skew angle of 40 to 50 degrees was suggested, and these vortices were thought to be the possible cause of large horizontal response.Then the response and fluctuating wind velocity were measured simultaneously, and conditional sampling based on the occurrence of large responses was conducted to clarify the fluctuating wind velocity characteristics causing the large response. These were some cases where fluctuating wind velocity that acts on the bridge model with skew front line of around 40 degrees caused large responses, and that was considered to correspond to the vortex structure suggested in the flow visualization experiment.On the other hand, there were other cases where these fluctuating wind velocity characteristics were not observed, or reproduction of the experimental results was not good. The cause is now sought considering sensitive effects by flow condition etc. Also the aerodynamic force characteristics are to be measured using simultaneous pressure measurement experiment.