【作者】 李玉梅；

【导师】 周慎杰；

【作者基本信息】 山东大学 ， 工程力学， 2008， 硕士

【摘要】 随着社会进步和技术的不断发展,以及各施工企业对高效益和高效率的执着追求,整体吊装工程越来越普遍,这就要求吊装用起重机的起重能力、作业幅度和高度越来越大。起重机日益向着大型、高耸、轻柔、格构化方向发展。由于高强度钢材的大量采用,提高了结构强度,却使刚度和稳定性问题日显突出。复杂桁架式结构的稳定性分析成为当代大型起重机结构设计计算的难点。履带起重机的臂架是由钢管焊接而成的大型空间超静定桁架结构,工程中常使用有限元法来进行设计计算,具有主副臂结构的履带起重机格构式臂架的整体稳定性分析更是目前我国起重机设计分析人员所面临的难题。因此,结合起重机设计规范,寻求简单、实用、有效的方法极为必要。通过对起重机吊臂的受力分析,采用了用放大系数法求截面弯矩,从而用应力法校核其稳定性;引入了悬臂式结构端部水平位移的便捷算式。在此基础上,通过位移比较的方法,引入了双肢格构式构件和四肢格构式构件等效为实腹构件时等效惯性矩的计算公式。在不改变构件长度的情况下,实现了格构式结构到实腹式结构的等效。通过等效惯性矩的计算方法,对变截面格构式构件的稳定性计算进行了初步的探讨,引入了两端铰支的变截面梁失稳特征方程。为研究弯曲梁的失稳问题打下了基础。对两节梁组成的弯曲梁在横向力和竖向力作用下的失稳问题进行了研究,通过建立每节梁临界状态下弯曲和扭转变形微分方程,根据杆件变形的边界条件以及杆件之间的变形协调关系,得出了一端固定一端悬臂的弯曲梁在横向力和竖向力作用下平面外失稳的特征方程,并进行了讨论。对具有主、副臂结构的履带起重机格构式臂架的整体稳定性进行了研究,给出了具有主、副臂结构格构式臂架失稳的临界载荷的计算方法和采用应力法校核稳定性的方法。以具体的实例给出了具有主副臂结构的履带起重机格构式臂架整体稳定性的计算方法和步骤。更多还原

【Abstract】 With the constant development of society and technology, as well as, the unremitting pursuance of the construction enterprises for more benefits and higher efficiency, integrative suspension-and-installation projects become more and more prevalent, thus caused a more and more demanding request of lifting ability, working extent and height of the cranes used for suspecting and installing. Modern cranes tend to be larger, higher, more ingenious and lattice structural. The adoption of ample high-strength steels has improved the structure strength, but it has also made the problem of intensity and stability more conspicuous at the same time. The stability analysis of complex truss structure gets to be the nodus of the calculations in the structure designs of modern good-size cranes. Tracklayer-cranes’ arms are good-size space-hyper-static truss structures made up by jointing steel tubes. The finited-element technique is often used to perform calculations in designs in projects. The analysis of integrative stability of the lattice structural arms of tracklayer-cranes with main & subsidiary arms is even the puzzle for designers and analyst in our country. So we conclude that it is very necessary to seek for pithy, practical and efficient techniques following crane designing criterions.By analyzing force bearing status of cranes’ arms, adopting enlarge-coefficient techniques to work out section bend quadrature, then we can use stress technique to collate the integrative stability of it.A convenient formula to calculate the horizontal displacement of the cantilevered end was introduced. On this basis, by a method to compare the displacements, a formula was reached to calculate the equivalent inertia quadtature, when two-limbs lattice structural component and four-limbs lattice structural component are equal to abdomen-solid component. Without changing the length of components, the equivalence between the lattice structures and abdominal structures has come true. Through the method of calculating the equivalent inertia quadtature, we conducted a preliminary study about the stability calculation of variable cross-section lattice members, and reach to a characteristic equation which describes the stability-losing of the variable cross-section beam which was hinged at both ends.The stability-losing problems of bending beam which is component of two beams and under the force from horizontal and vertical directions have been studied, through the establishment of differential equations of each beam bending, reversing and deformation under the critical state, according to the boundary conditions of bar deformation and coordinating relations between the transformative bars, we achieved a characteristic equation that describes the stability-losing beyond the plane of the bending beam whose one end was fixed and the other was cantilever when it is under the force from horizontal and vertical directions, and had a discussion.Studied the integrative stability of the lattice structural arms of tracklayer-cranes with main & subsidiary arms, the methods to calculate stability critical load in and out of the lattice structural jibs with main & subsidiary arms lifting plane and using stress technique to collate the integrative stability are presented. Specific examples are given to show the method and steps to calculate the the integrative stability of the lattice structural arms of tracklayer-cranes with main & subsidiary arms.更多还原