Simulation of pavement roughness and IRI based on power spectral density

The international roughness index (IRI) for evaluating pavement surface roughness is simulated using the power spectral density (PSD) of pavement surface fluctuation. Quarter-car models recommended by the World Bank for measuring pavement roughness are adopted to simulate vehicle response. Surface roughness in time domain is generated based on 36 known PSDs of roughness. Newmark sequential integration method is employed to conduct the simulation of quarter-car motion. Statistical analysis of system output shows that the IRI is linearly correlated with the standard deviation of relative vertical velocity between the axle and sprung mass. A linear regression equation is obtained, based on which further analysis is conducted to represent the IRI in terms of PSD roughness. It is found that if PSD roughness is expressed as a polynomial function, the IRI can be simply calculated by means of the square root of the sum of the weighted regression coefficients of PSD roughness. The weighting coefficients are provided and can be conveniently used in practice.