Non-probabilistic Reliability Study Of Truck Crane Boom System

Box--sectioned boom is one of the most important components of truck crane, and strength, rigidity and stability of the boom structure determine truck crane's overall structure safety and performance. The safety-factor-method, currently, is commonly applied in conventional design and calculation. When the truck crane working, the lifting load, the dynamic load factor and the lifting objects yaw angle, and the like, are usually not constant; in contrast, they are indefinite variables, interval variables or their combination, which however are still considered as constant values. So, consequently, the above method does not take reliability into consideration.Probability model is used to describe the uncertain variables in conventional reliability method, and application basis of probabilistic model is the existence of a large number of samples and the repeatability of events. Studies have shown that probability model of a small deviation could lead the calculation results to a great error; when lacking of adequate data to describe the probabilistic model, the probabilistic reliability calculation method is not reliable. Truck crane, on the other hand, is a kind of very expensive construction machinery and is manufactured mainly in form of small-batch production, so that it is difficult to collect enough samples to establish a more accurate probability model. Structural non-probabilistic reliability theory, however, can make full use of limited information available based on intervals, in which method there is no need to analyze distribution form but determine the boundary of the non-determined parameters in order to figure out the reliability of response and design boom considering both structure and reliability.In this paper, the lifting loads, yaw angle and dynamic load factor were taken as non-determined variables for truck crane design with hexagon box-sectioned boom, and then moments caused by the axial load, horizontal load as well as eccentric load on luffing plane and variation range of side load on rotary plane were calculated. Then the non-probabilistic reliability of rigidity, strength, overall stability and local stability were studied, and with help of practical examples the regular computation and non-probabilistic method for crane boom design were combined properly. The oval box-sectioned boom of 100t truck crane was optimized by non-probabilistic reliability analysis, so that the weight could reach the minimum under the condition that strength, rigidity, and stability all satisfy the requirement. The relation among diameter of outer circle, length of topside and distance between circle center to topside was analyzed to figure out the influence caused by the spontaneous changing and independent changing of above three variables on the weight and reliability of boom system, which provides useful reference for truck crane boom designers.