在水平变幅塔式起重机上,多采用受力明确、结构简单的正置三角形断面平行弦杆臂架。其吊点布置通常有两种型式:一种布置在上弦杆(简称上支承式),另一种布置在下弦杆(简称下支承式)。下支承式的采用已有较长历史,上支承式则近年来才被采用。塔机设计人员关心的是两种支承型式各有何特点,在采取不同支承型式时应如何决定其位置以及何种为好等问题。本文就内力 In the horizontal luffing tower crane, the use of more force, simple structure of the triangular cross-section parallel chord boom. There are usually two types of hanging point arrangement: one is arranged on the winding rod (upper bearing type) and the other is arranged on the lower chord (lower bearing type). The lower support has been used for a long time, and the upper support has only been adopted in recent years. Tower crane designers are concerned about the characteristics of the two types of support, how to determine the location and what kind of problems should be taken when adopting different types of support. This article on internal forces