轨道-路基体系一致动力相似设计方法与动力试验

在室内动力试验中,为考虑缩尺模型轨道和路基结构的动力效应以及二者的相互作用,提出了轨道-路基体系一致动力相似设计方法:即在对轨道结构进行动力相似设计的同时,保持轨道-路基模型的加速度相似比为1,再通过轨道和路基遵循相同的长度相似比、控制路基模型剪切波速相似来进行路基结构动力设计.采用该方法进行了缩尺比为1/4的轨道-路基模型结构的相似设计,开展了不同激振频率工况下模型体系的动力试验,测试并分析了路基模型不同位置处的加速度反应等,确定了试验模型体系一阶固有频率.结果表明:加速度在向下传递过程中存在时间尺度上的滞后效应;同一激振频率下,路基不同结构层处加速度频谱分析的特征频率一致.

Uniform Dynamic Similitude Method and Experimental Study for the Track-Subgrade System

In order to consider the dynamic responses of track and subgrade of the scaled track-subgrade model and the interaction between them, a uniform dynamic similitude method for the track-subgrade system was first proposed. The dynamic similitude design of the track was conducted and the acceleration-scaling factor of the track-subgrade model was assigned as 1.0. Then, the track and subgrade follow the same length scaling factor and the shear wave of the subgrade model was controlled to perform the dynamic design of the subgrade structure. By using the proposed approach, the similitude design of a 1/4-scaled track-subgrade model system was conducted and a series of dynamic tests of the model system under the excitations with different frequencies were carried out. The acceleration responses of different positions of the model were measured and analyzed. The first-order frequency of the test system was obtained. The results show that there exists time delay in the process of downward transfer of acceleration. Under the excitations with a certain frequency, the characteristic frequencies, which were obtained by using the spectrum analysis of acceleration, of different structural layers are consistent.