The Study Of Crane Structure Design Based On Limit State Method

The main objective of crane structure design is to make the structure satisfy all kinds of prospective functions in scheduled service period on the premise of economy, namely, possess enough reliability. In order to achieve this objective, a scientific and reasonable structure design method is very important. Allowable stress method has been used many years, but after all, it has some defects in theory and practice. Limit state method, based on the theory of reliability and probability, depends on the probability that the structure accomplish its prospective functions to weigh reliability. It is more scientific and reasonable than allowable stress method, as it depends on general safety factors. Therefore the development of crane structure design from allowable stress method to limit state method indicate the development from the fixed value method to the probability method, and from the qualitative analysis phase based on experience to quantitative analysis phase based on statistic math. It is an important advancement of the structure design thoughts and methods.Now some countries have started studying how to use limit state method in crane structure design, and some standards have had correlative contents. The study on the method is late in our country. Allowable stress method is still used in the current design rules for cranes. It is necessary to do systemic studies on limit state method, and to apply the method in crane structure design of our country.In this thesis, based on the theory and application of limit state method in construction , some kind of correlative rules and standards, the limit state method theory of the crane structure is studied, including the calculating method of reliability, the statistic analysis method of loads and structure resistance, and the method of determining object reliability index. Meanwhile, the limit state method is contrasted with the allowable stress method in theory. After that, the practical limit state design method of crane structure is studied, including the method of determining partial load factors, resistance coefficient, and important coefficient. As an example, the lattice boom of crawler crane is calculated by these two methods. The results verify that the limit state method is better than the allowable stress method. Compared with limit state methods and their different rules, the allowable stress method is revised. It is hoped to solve some problems of the allowable stress method, to contribute to the revision of the design rules of cranes in our country and the design of other mechanism, and to improve the design quality and reliability of mechanism.