This article analyses and proposes suitable approaches to improve frame structures in term of weight reduction for heavy-duty truck chassis frame in general and semi-trailer frame in particular. Specifically, this study focused on reducing the weight of frame side members, which makes up the primary mass of the vehicle chassis. Some variants of design to evaluate its efficiency and applicability on semi-trailer frame were proposed. The study explored maximum stress and deformation within the frame structure under static loading conditions using the integrated finite element analysis and multi-body simulation based on which some modified designs from the existing frame was proposed to reduce the weight of the chassis frames, including altering the main beam's material property, cross-section dimension, or lightening holes. The analysis results were presented in plots of the stress and deflection spectrum of the frame in numerical simulations. The proposed approaches were analysed and discussed to find out the appropriate improvement method for the heavy truck frame and the semi-trailer frame suitable for the truck manufacturers in Vietnam.