The influence of shearing forces and mass inertia on the interpretation of 4PB test results in the case of asphalt mixtures tested in two different devices

Abstract

ABSTRACT The main goal of the article is to analyse that taking into account shearing forces and the mass of the test system elements during four-point bending has an impact on the determined stiffness moduli and phase lags of asphalt mixtures in a wide range of frequencies and temperatures. Such an analysis is made possible by a computational model created using the Timoshenko beam theory and an inverse analysis program written in Excel software. It is shown that the impact of taking into account transverse forces is significant (differences of up to 7%) while taking into account the inertia of moving elements (values adopted for real devices) does not have a significant impact on the results obtained. As the tests were carried out using two measuring devices (small and large) on an asphalt concrete mixture with a maximum aggregate size of 22 mm, the influence of the size of the tested beam and its cross-section in relation to the maximum aggregate size on the obtained results was also analysed. In the case of statistically valid data, it was shown that the values of stiffness moduli in the small device were greater by about 13% than those obtained in the large device.