Adaptive Decommissioning Mechanism For Metal Structures Of Bridge Cranes Oriented To Environmental Properties

General overhead crane is a kind of special equipment for hoisting and handling items,widely used in steel metallurgy,equipment manufacturing,equipment maintenance and material handling.Bridge structure,the "skeleton" of whole machine,is an important part of the equipment,playing a key role in carrying and load transfer.At present,there is a lack of research on the decommissioning mechanism of the bridge structure of general overhead cranes at home and abroad,and there is no standard and theoretical support for timely retirement.As a result,many structures are either scrapped ahead of time or in service over a period of time.The former has low resource and energy utilization rates,while the latter causes major security risks.Therefore,scientifically,comprehensively and effectively determining the decommissioning mechanism of the bridge structure is the only way to avoid major accidents,reduce waste of resources and energy,and then achieve the goal of "double carbon".1)Load capacity calculation.In order to avoid the insufficient load capacity of the bridge structure due to unreasonable design under the ultimate working conditions,the load capacity of the bridge structure is verified based on the limit state method.To ensure that the structure will not have plastic deformation or instability in the early stage of service,and provide an index quantification method for structural safety and green comprehensive performance evaluation.2)Adaptive equivalent load spectrum prediction.Aiming at the difficulty of implementing large-scale and equal-proportional load spectrum tests for general overhead cranes,only predicting large samples from small samples measured in a fixed period of time will reduce the accuracy of the prediction results over time.From the perspective of iterative update of small samples,an adaptive equivalent load spectrum prediction method based on the lion optimization algorithm is proposed to improve the relevance vector machine.According to the load characteristic information,an acquisition system is built to obtain sample data for prediction.Based on the traditional lion optimization algorithm,the improved algorithm is formed by introducing Logistic chaotic map and dynamic search interval.In this way,the hyperparameters of the relevance vector machine model are optimized and packaged into the equivalent load spectrum prediction model with the best accuracy under the current measured data.According to the sample distribution of the load characteristic information,combined with the Latin hypercube sampling,the prediction of the load spectrum under the regular inspection period is completed.Using the iterative update mechanism of the load acquisition information,the above predicted load spectrum is adaptively modified,so as to achieve the purpose of multiplying the load spectrum,and also provide the load characteristic basis for the calculation of the fatigue residual life of the in-service equipment.3)Fatigue life assessment.In view of the problems of short life of strain gauges,tedious and time-consuming patching process,and large amount of labor or material resources consumed in the field stress measurement process,the remaining life assessment method of bridge structure based on equivalent load spectrum is adopted for structural life prediction.Based on the equivalent load spectrum after flourishing,the information is extended according to the limit running distance to obtain the loading and unloading positions of the crane and trolley under each working cycle.The metal structure design theory is used to determine the dynamic effect of load during the working cycle,combined with the structural mechanics method to calculate the internal force influence line of the bridge structure during the moving load motion and extract the stress history of the danger point.The three-point rainflow counting method is used to extract the two-parameter spectrum in the stress history,and the fracture mechanics theory is used to obtain the fatigue remaining life and crack expansion of the bridge structure,which provides the calculation method of the remaining life index for the comprehensive performance evaluation.4)Comprehensive performance evaluation.In order to comprehensively consider the structural safety and greenness of the general overhead crane in service,the environmental impact potential calculation method based on the equivalent load spectrum is proposed to form a comprehensive crane performance evaluation program for the decommissioning mechanism of the bridge structure.The fuzzy comprehensive evaluation method is used to construct a comprehensive evaluation system for the safety and green performance of the bridge structure.The load spectrum prediction method and the life assessment method are used to quantify the safety indexes in the system.Based on the three-scale hierarchical analysis method and CRITIC method,the weight of each safety index is determined by the combination of sequential information and intensity information assignment method.The electric energy value consumed by operation of driving structure during the working cycle is converted into the green evaluation index value,and each index is weighted.Combined with the fuzzy comprehensive evaluation matrix,the total score of comprehensive performance evaluation is obtained.Based on the prediction result of adaptive equivalent load spectrum,the change law of comprehensive performance evaluation result of bridge structure with time is explored to provide decision data for adaptive decommissioning mechanism of general overhead crane bridge structure.5)Decommissioning decision.For the decommissioning of the bridge structure of general overhead cranes,the adaptive decommissioning mechanism is established by taking into account the change process of the user’s economic benefits and the comprehensive performance of the structure.The AHP-TOPSIS multi-objective decision-making method is utilized to determine the optimal decommissioning time by combining the year-to-year changes in both the cumulative economic benefits of the crane and the comprehensive performance of the structure.Based on the historical service information,the initial crack length a and the remaining life n of the current hazardous section are determined,and the predicted equivalent load spectrum for the next n years is updated with the in-service state data to update the optimal decommissioning time point.An important theoretical basis and feasible implementation plan is provided for the decommissioning decision of the general overhead crane bridge structure.