| Constrained damping structure can reduce the vibration and noise with excellentdamping performance effectively caused by underground railway, relieving impact onthe normal life of residents. So studying the damping performance and its influencingfactors of constrained damping structure is very important.In the paper, based on Qingdao subway under construction, firstly, it studied thebasic mechanical properties of viscoelastic damping material Qtech503, includingtensile strength, elongation at break, cure time, solid content, hardness, etc. Then itmade various constrained damping structure as Qtech503is damping layer. It studiedthe influence law of the different forming method of damping layer, the thickness ratioof damping layer and basement layer and the thickness of constrained layer onconstrained damping structure. The conclusions are listed as follows:(1) Research on the basic properties of Qtech503shows, the tensile strength ofQtech503grows gradually with the development of time and is7.90MPa when time is20d, which has reached98.5%of maximum. The elongation at break of Qtech503reduces gradually with the development of time and is344.56%when time is12d,which has reached73.06%of end value. The cure time of Qtech503can not onlyguarantee the good adhesion performance to base material but also saves constructiontime, shortens the construction period and achieves good economic benefits. The solidcontent is93.13%, film density, and Qtech503is viscoelastic damping materials withhigh solid content and environmentally friendly standard. The hardness of Qtech503grows faster firstly then slower and is A57at12d, basically complete development.With increasing of temperature, the storage modulus decreases and the material lossfactor increases firstly then decreases. The change curve of storage modulus and lossfactor about Qtech503was affected by frequency.(2) Research on damping performance influenced by different forming method ofdamping layer shows, in the constrained damping structure, the compound loss factorincreases gradually and the vibration extreme value decreases when the forming method is prefabricate (PR), geotextile prefabricated (GP) and cast-in-place (CIP) respectively.The compound loss factor has minimum and the vibration extremum has maximumwhen the forming method is PR. The compound loss factor has maximum and thevibration extremum has minimum when the forming method is GP. The compound lossfactors are0.1145,0.1236and0.1542and the vibration extremums are62dB,60dB and52dB respectively, when the thickness of damping layer is1.0mm. Forming methods ofCIP and PR have best and worst damping performance of all.(3) Research on damping performance influenced by thickness ratio of dampinglayer and basic layer shows, in the constrained damping structure, the compound lossfactor increases gradually with thickness ratio in5/150~40/150and gets maximum andthe vibration extremum takes the minimum at40/150. When the thickness ratioincreased to50/150, the structure of the damping performance lowers slightly. Sodamping performance is better at40/150.(4) Research on damping performance influenced by thickness of constrained layershows, in the constrained damping structure, with the increasing of the thickness ofconstrained layer, compound loss factor increases firstly and decreases later andvibration extremum decreases firstly and increase later. The loss factor obtains themaximum and the average of vibration extremum gets minimum, when the layerthickness of constrained layer is20mm. Taking2order compound loss factor forexample, compound loss factor are0.1257,0.1538,0.1781,0.1683and0.1623respectively, when the thickness of constrained layer is10mm,15mm20mm,25mm and30mm respectively.Based on the above research, it have obtained the changing rule of Qtech503basicperformance and the damping performance of constrained damping structure underdifferent influencing factors, to provide basic data and theoretical support for theengineering application. |
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