随着科学技术的不断进步，动臂塔机结构逐渐向大型化发展，起重量和工作速度不断提高。臂架作为起重机的重要支撑结构件，其重量在整机中占很大比重，并且过大的自重会严重影响起重机的起重能力。为了降低起重机臂架的重量，提高整机工作性能，开始对起重机臂架的弦杆使用轻质高强度合金钢。但多数情况下该桁架结构并不能充分利用材料的性能。针对上述问题，本文做了以下研究工作： 以FZQ2000Z型动臂塔式起重机的桁架式臂架结构为研究对象，分析了该起重机的结构及工作原理，探讨了臂架变幅平面和回转平面的载荷分布，研究了各工况下臂架的受力特点，确定了起重机臂架结构稳定性最差时臂架的长度和仰角的范围；运用ANSYS有限元软件，建立了多载荷组合条件下臂架结构的有限元分析模型，分析了最差稳定性时，臂架的最大承载能力和最大破坏吊重；通过对弦杆结构的改进，采用轻质高强度合金钢D562替换普通钢Q390，分析了此时臂架的弹塑性力学特性，确定了臂架弦杆、腹杆强度的最大利用率，结果表明用800MPa级超高强度合金钢D562替代常规Q390钢后，不但可以满足实际需要还可减轻臂架自重约30％，采用高强度钢材后臂架轴向压缩变形量增大，其中额定载荷工况水平位移的最大值为增加4.1%；最后，运用有限元模态理论分析理论，建立了起重机臂架的有限元模态分析模型，分析了臂架系统自振频率以及臂架整体结构的刚性。 本研究为合理选择钢材、设计桁架结构，探索起重机臂架的力学特性及相关设计规律，提升臂架承载性能降低重量，提供理论依据。

With the continuous progress of science and technology, the structure of the boom tower is gradually developing to a large scale, and the weight and working speed are constantly improved. Cantilever crane as an important supporting structure of crane, its weight occupies a large proportion in the whole machine, and excessive self-weight will seriously affect the crane's lifting capacity. In recent years, in order to reduce the weight of crane boom and improve the performance of the whole machine, people have begun to use lightweight high strength alloy steel for the boom of crane boom. But in most cases, the structure of the truss does not make full use of the properties of the material. In view of the above problems, this paper has done the following research work: The structure and working principle of the truss type arm frame of the FZQ2000Z type boom tower crane are studied. The load distribution of the arm frame's amplitude plane and the rotary plane is discussed. The force characteristics of the arm frame are studied, and the length and the pitch of the arm frame when the stability of the crane arm is the worst is determined. With the ANSYS finite element software, the finite element analysis model of the arm frame structure under the condition of multi load combination is established, and the maximum bearing capacity and maximum failure lifting weight of the arm are analyzed when the worst stability is analyzed. By the improvement of the string structure, the lightweight high strength alloy steel D562 is replaced by the ordinary steel Q390, and the analysis is made. The elastoplastic mechanical properties of the time arm frame determine the maximum utilization of the strength of the arm and the abdominal rod. The results show that the replacement of the conventional Q390 steel with the 800MPa super strength alloy steel D562 can not only meet the actual needs but also reduce the weight of the arm frame by about 30%, and the axial compression deformation of the rear arm of high strength steel is increased. The maximum value of the horizontal displacement of the rated load condition is increased by 4.1%. Finally, the finite element modal analysis model of the crane arm is established by using the finite element modal theory analysis theory, and the vibration frequency of the arm frame system and the rigidity of the overall structure of the arm frame are analyzed. This study provides a theoretical basis for reasonable selection of steel and design truss structure, exploring the mechanical characteristics and related design rules of cantilever crane, improving bearing capacity and reducing weight of cantilever crane.