**5.1 The effect of the stubs on the lower frequency complete BGs**

**Figure 14** displays the evolution of the first complete bandgap as a function of the steel-stub height, hS. We can find that, with the increase of the steel-stub height, both the lower and upper edges of the first complete shift to a lower frequency range firstly and then move to higher frequency range. For example, when the steel-stub height is less than or equal to 3 mm, with the increase of the steel-stub height, the lower edge shifts to lower frequencies, but when the rubber stub height is larger than 3 mm, the lower edge frequency shifts to higher frequencies as the steel-stub height increases.
