Author(s): Marcocci Sébastien
Expansion joints constitute an important element in the conception of a bridge. In Wallonia the Administration has define several rules and steps to fulfil before the installation of a new device. These requirements concern only the technical aspects without regarding the acoustical one. Years after years the Administration has to deal with plains concerning the noise coming from the expansion joints from people living close to bridges.\n\nConsidering the demand of people and in order to characterize the noise coming from these devices the Noise division of the Administration has been in charge to study the possibilities to define a method. It is important to precise that a “Walloon method” had already been used several years ago but the analysis of the results was not relevant. \n\nThe Administration was looking for an in situ method in order to characterize the joint in its environment. After the analysis of the European literature dealing about this problem five methods have been identified. Due to several practical aspects it was decided to study the Dutch method (RTD 1007-3) and to compare it with the one used in Wallonia. \n\nAn analysis of the RTD 1007-3 has also been done. The Dutch method consists of the comparison between the noise levels measured at 3m from the ground and at 7.5m from the centre of the lane. These are made right on the joint and at the surface upstream and downstream of the joint. Finally the joint is considered as valid if the difference between the levels are less than 5dB(A).\n\nL_joint – L_surface ≤5dB(A)\n\nBecause of the SPB method it is necessary to take into account the 7.5m long between the microphone and the centre of the lane. This parameter could be a problem because this distance is not available in most situations. \n\nFor this reason a second study has been done by measuring the levels at 7.5 meters and at 5 meters from the centre of the lane. A first step was to use a “theoretical” law on the 5m results and compare them with the other ones. The verifications due to the method were applied and the results compared. \n\nAfter contacted them the Dutch authorities indicate that using a “comparative” method the most important element is the distance of all the microphones from the centre of the lane. Taking this into account the analysis was done considering the same position for all the microphones. The measurements are done on several types of expansion joints in order to compare them. \nSeveral measurements were done in order to know the characteristics of the joints on the bridges better. The most of them are compliant with limit of 5dB(A) but is this limit enough in every cases? Could we use more restricted limits for joints closed to dwellings? In which conditions and accuracy? Is this limit valid for all types of expansion joints? \n\nThese elements will help to build a data base of expansion joints and may in the future become a central element for the choice of new devices in Wallonia.
Name: Mr Sébastien Marcocci