Two kinds of damping structures

annular free damping structure and annular constrained damping structure

were designed to simulate the structure used in the damping system of subway shield tunnel.Through the free beam single-point excitation experiment

the effect law of the thickness of the damping layers on the damping performance

such as composite loss factor and vibration acceleration level

was discussed.Then

the optimal thicknesses of the damping layers of the two kinds of structures were found.The experiment results of annular free damping structure show that when the thickness of damping layer ranges from 1mm to 7mm

the vibration acceleration amplitude i

s reduced by 1.1%

6

5.6% respectively than the undamped structure.Meanwhile

the composite loss factor and its amplification increase

but the vibration acceleration level reduces gradually.The experiment results of annular constrained damping structure show that when the structure is undamped and the damping layer thickness of the damped structure are1 mm and 3mm

the composite loss factor of the latter are increased by 18.75%

8.91%respectively than the former.On the other hand

when the thickness increases to over 3mm

the composite loss factor changes little.Results of this research indicate that the damping performance of annular free damping structure increases with the increase of damping layer thickness.The annular constrained damping structure has better damping performance when its damping layer thickness is 3mm.