《起重机介绍外文文献翻译@中英文翻译@外文翻译》由会员分享，可在线阅读，更多相关《起重机介绍外文文献翻译@中英文翻译@外文翻译（9页珍藏版）》请在金锄头文库上搜索。
1、附 录外文文献原文：The Introduction of cranesA crane is defined as a mechanism for lifting and lowering loads with a hoisting mechanism Shapiro, 1991. Cranes are the most useful and versatile piece of equipment on a vast majority of construction projects. They vary widely in configuration, capacity, mode of
2、operation, intensity of utilization and cost. On a large project, a contractor may have an assortment of cranes for different purposes. Small mobile hydraulic cranes may be used for unloading materials from trucks and for small concrete placement operations, while larger crawler and tower cranes may
3、 be used for the erection and removal of forms, the installation of steel reinforcement, the placement of concrete, and the erection of structural steel and precast concrete beams. On many construction sites a crane is needed to lift loads such as concrete skips, reinforcement, and formwork. As the
4、lifting needs of the construction industry have increased and diversified, a large number of general and special purpose cranes have been designed and manufactured. These cranes fall into two categories, those employed in industry and those employed in construction. The most common types of cranes u
5、sed in construction are mobile, tower, and derrick cranes.1. Mobile cranesA mobile crane is a crane capable of moving under its own power without being restricted to predetermined travel. Mobility is provided by mounting or integrating the crane with trucks or all terrain carriers or rough terrain c
6、arriers or by providing crawlers. Truck-mounted cranes have the advantage of being able to move under their own power to the construction site. Additionally, mobile cranes can move about the site, and are often able to do the work of several stationary units.Mobile cranes are used for loading, mount
7、ing, carrying large loads and for work performed in the presence of obstacles of various kinds such as power lines and similar technological installations. The essential difficulty is here the swinging of the payload which occurs during working motion and also after the work is completed. This appli
8、es particularly to the slewing motion of the crane chassis, for which relatively large angular accelerations and negative accelerations of the chassis are characteristic. Inertia forces together with the centrifugal force and the Carioles force cause the payload to swing as a spherical pendulum. Pro
9、per control of the slewing motion of the crane serving to transport a payload to the defined point with simultaneous minimization of the swings when the working motion is finished plays an important role in the model.Modern mobile cranes include the drive and the control systems. Control systems sen
10、d the feedback signals from the mechanical structure to the drive systems. In general, they are closed chain mechanisms with flexible members 1.Rotation, load and boom hoisting are fundamental motions the mobile crane. During transfer of the load as well as at the end of the motion process, the moto
11、r drive forces, the structure inertia forces, the wind forces and the load inertia forces can result in substantial, undesired oscillations in crane. The structure inertia forces and the load inertia forces can be evaluated with numerical methods, such as the finite element method. However, the driv
12、e forces are difficult to describe. During start-up and breaking the output forces of the drive system significantly fluctuate. To reduce the speed variations during start-up and braking the controlled motor must produce torque other than constant 2,3, which in turn affects the performance of the cr
13、ane.Modern mobile cranes that have been built till today have oft a maximal lifting capacity of 3000 tons and incorporate long booms. Crane structure and drive system must be safe, functionary and as light as possible. For economic and time reasons it is impossible to build prototypes for great cran
14、es. Therefore, it is desirable to determinate the crane dynamic responses with the theoretical calculation.Several published articles on the dynamic responses of mobile crane are available in the open literature. In the mid-seventies Peeken et al. 4 have studied the dynamic forces of a mobile crane
15、during rotation of the boom, using very few degrees of freedom for the dynamic equations and very simply spring-mass system for the crane structure. Later Maczynski et al. 5 studied the load swing of a mobile crane with a four mass-model for the crane structure. Posiadala et al. 6 have researched th
16、e lifted load motion with consideration for the change of rotating, booming and load hoisting. However, only the kinematics were studied. Later the influence of the flexibility of the support system on the load motion was investigated by the same author 7. Recently, Kilicaslan et al. 1 have studied the characteristics of a mobile crane using a flexible multibody dynamics approach. Towarek 16 has concentrated the influence of flexible soil foundation on
