图3. $\alpha = 1 / 2L$时同截面对偶梁前三阶最大位移归一化振型(第一阶：黑色,第二阶：红色,第三阶：蓝色)

Fig. 3. The normalized displacement mode shapes of a dual of beams with identical cross-sections (the 1st order: black, the 2nd order: red, the 3rd order: blue)