The Calculation of Bending Moment in Beam by the Three-Moment Equation for the Design of Trailer Chassis

Abstract

For the current design of the chassis of a trailer, the chassis is determined as a simply support beam for ease of estimating the bending moment arising from the payload. However, the value of the bending moment estimated by such method is greater than the actual value. According to this issue, this paper therefore proposes an alternative equation that can be used to more accurately estimate the bending moment in the chassis. The equations are created based on three-moment equation and used to analyze the bending moments and bending stresses that occur in the chassis, presented through a case study. The results obtained from the equations are compared with the results obtained from the finite element (FE) model to confirm the validity of the equations. The comparison results show that the results calculated with the equations created are no more than 5% different from those of the FE model. Therefore, the equations developed in this research are reliable. In addition, the case study shows that the maximum bending moment value calculated with equations in this research was 31.9% less than traditional calculations. When such bending moment value is taken into the consideration for selecting the cross-sectional size of steel for making chassis, it resulted in a 17.9% reduction in the weight of the chassis. Therefore, using the equations developed in this research, the designed chassis has lower weight and production costs compared to traditional designs.