Dynamic Analysis of Infinite Beam on Modified Vlasov Subgrade

Abstract

Analysis of pavement-subgrade system under traffic load has been traditionally done by static method, such as multilayer elastic theory. Although, in some instances, the static analysis method is sufficient and conservative for the daily practice, truly dynamic analysis is needed in some special cases, such as shallow bedrock with high vehicle speed. Furthermore, interpretation of nondestructive testing data from falling-weight deflectometer (FWD) and Dynaflect tests requires the use of more rigorous dynamic back-calculation techniques. Presented in this paper is an efficient dynamic analysis procedure for the interaction behavior of an infinite beam on a modified Vlasov subgrade. A complete description of the dynamic analysis procedure is given, followed by a comprehensive parametric study to investigate the effects of subgrade depth, the material stiffness and damping ratio, and vehicle speed, on the calculated beam response. The analysis results indicate that the subgrade depth exerts significant influence on the beam response. Increasing vehicle speed only causes a small amount increase in dynamic displacement under the load. An efficient back-calculation algorithm based on the derived dynamic compliance function is also developed in this paper. Two case studies are given at the end of this paper to illustrate the accuracy and convergence rate of the developed back-calculation algorithm. The developed dynamic analysis procedures (both forward and back-calculation) are implemented into personal computer (PC) based computer program for field application.