凹底平车设计中几个问题的研究（下）张俊克，刘晓林，吕俊超４．４大底架横截面如何利用各限界所允许的有效空间，选择合适的截面形式，在保证强度、刚度和满足工艺要求的前提下，必须优化大底架横截面结构型式。为便于研究和应用，提出一些比较常用的三种型式，并加以比... Study on Several Problems in the Design of Concave Car (Part 2) Zhang Junke, Liu Xiaolin, Lv Junchao 4.4 How to Use the Effective Space Allowable by Each Limit in Major Cross Section How to choose the suitable cross section, To meet the technical requirements of the premise, we must optimize the cross-sectional structure of the large chassis type. For ease of research and application, put forward some of the more commonly used three types, and to be more than ...