| Container cranes are main equipment and symbol of container internals, nowadays container crane's status and function are paid much more attention. As important technological foundation of port, container crane is able to show seaport's productivity level. For bridge container crane the cost of steel structure occupy a majority of total costs, and service life of bridge container crane lie on that of steel structure.With the development of economy, more and more container cranes were put into service, at the same time some problems are brought out such as safety. User always hope the service life of crane is much longer because of high price of crane, but most of cranes in service was manufactured in 1980's or even more early, at that time engineers design the crane inconsiderate of according to fatigue, so it is very necessary to implement the evaluation of reliability of crane steel structure.A 5-grade comprehensive evaluation method for reliability assessment of steel structure of bridge container crane is presented in this paper. The evaluation of steel structure of bridge container crane includes five levels: single part contributing factors, single part, subsystem, whole steel structure and the combination property of the crane structure. The traits of this method are as follows:1. Quantitative analysis of contributing factor and the establishment of the membership function by analogy method. The membership function, which is able to describe fuzzy distribution more accurately, belongs to mountain range distributing.2. Determination of the weight value of each factor according to its significance by the analytic hierarchy process (AHP). In general, the weight value is presented directly according to experience, but it is difficult to decide the weight value accurately when the contributing factors' number is very large. The method of AHP gets the weight value according to all one-one weight value, hi order to avoid cycle contradiction in judgment matrix the weight value need to be inspected by coherence.3. Use of the weighted average model in reliability assessment of steel structure of bridge container crane. This model thinks over fully contribution of all factors, so the conclusion is more reasonable.4. Classification of the quality grade of steel structure of bridge container crane also adopt to weighted average model.Many factors are represented in this paper about the evaluation of reliability of container crane, such as static intensity, dynamic intensity, fatigue intensity, static rigidity, dynamic rigidity, buckling and stability. This paper stress on the buckling, because buckling calculation of crane design specification does not include the beginning thedefects of thin plate, it isn't suitable to evaluate container crane that is used for many years. This paper study the calculation method of buckling of plate with beginning defects based on thin plate theory, that is small flexibility theory calculation method.In addition, a new method to obtain critical load of small flexibility plate is presented in this paper according to the traits of local stability in small flexibility plate. It is not appropriate in engineer field to calculate directly the critical load by small flexibility theory. As it's shown in flexibility chart that flexibility increase faster than load, in a other word, when load is more than some level, a little bit enhancement of load will cause tremendous flexibility enhancement, this is very dangerous in engineer. Based on this trait the new method presented in this paper is that the critical load of local stability of small flexibility plate is controlled by flexibility curve slope.Based on the theory of fuzzy comprehensive evaluation of reliability of steel structure of bridge container crane, this paper develops the software system of fuzzy comprehensive evaluation of reliability of steel structure of bridge container crane. This program keep to the flow of software engineer principle, this software system is developed by in... |
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