Traffic Vibration Damping With Innovative Materials: Development And Calibration Of a Simulation Model

The reduction of vibrations transmitted by transport infrastructures, without increasing too much the construction cost, is going to be a very important issue to deal with. The most effective construction techniques used up to now are based on very complex and expensive solutions (such as floating slabs) and on the use of special and once again expensive materials (such as elastomeric mats). One of the possible innovative techniques is based on the use of hot mix asphalt in which a share of the traditional aggregates is substituted with rubber granulate (2 – 4 mm) produced using waste tyres. This material could be used as sub ballast layer in railway constructions and as binder or base layer in road construction. “Modified” hot mix asphalt results in lower elastic modulus and higher loss factor compared with the traditional one, it can be produced with the same machines and procedures resulting in comparable costs, as a consequence it can be regarded as a very promising material to be used in the traffic vibration control field. The prediction of the effectiveness of vibration damping systems is very complex due to the number of variables involved and to the complexity of their relationships. Simulation and thence the possibility of a low cost “try and error” approach becomes in this context an obvious answer to the problem, but once again the complexity of the systems, the peculiar dynamic behaviour of involved materials makes reliable models hard to be defined and calibrated. The proposed approach is based on the calibration of the materials behavioural models comparing real and simulated results of manageable and repeatable experiments (such as the complex modulus test or tests on multilayer systems). The large amount of experimental data collected and evaluated allows first assessment on the best material composition (share of aggregate substituted with rubber granulated first of all), and on the more promising geometrical configurations, and leads to the definition of a reliable model suitable to be used to individuate best solutions.