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Flexible job shops motivated by small batches and multiple orders require the collaboration of machines and automated guided vehicles (AGVs) scheduling to boost shop floor flexibility and productivity. The joint scheduling of machines and AGVs can better achieve global optimization. However, joint scheduling requires two NP hard problems to be solved simultaneously. Therefore, this paper employs a multi-AGV flexible job shop scheduling problem (MA-FJSP) with an effective hybrid algorithm. First of all, a model is established with the objectives of minimizing the makespan, the total AGV running time and the total machine load. To solve the MA-FJSP, high-quality initialization methods and improved elite strategies are designed to improve global convergence in the proposed algorithm. In addition, a problem-knowledge-based neighborhood search is integrated to improve its exploitation capability. At last, a series of comparative experimental studies were performed to exam the effectiveness of the improved algorithm. The results demonstrate that the solutions gained by the proposed algorithm perform well in respect of convergence, diversity and distribution. [ABSTRACT FROM AUTHOR]

Owing to the light weight and high fundamental frequency, timber floors exhibit impulse-like responses under human-induced excitation, which is different with the resonance-like responses for heavy concrete structures. The vibration serviceability of timber floors thus needs to be considered in a different manner. Many design codes for timber structures have required that the static displacement or dynamic response under human excitation should be limited within a threshold for the purpose of serviceability, while failing to provide appropriate method for predicting structural responses considering various affecting factors. Inspired by the idea of response spectrum, this paper proposed a design-oriented method for the peak acceleration prediction of high-frequency floors under human bouncing excitation. The prediction can be obtained for any desired confidence level. Statistical analysis shows that the acceleration responses are mostly dependent on structural fundamental frequency, structural damping ratio, and excitation frequency, which are considered in the proposed mathematical model. The application procedure and the experimental assessment of the proposed model are provided, showing the decent applicability of the proposed method. [ABSTRACT FROM AUTHOR]

The vibration caused by human excitation has become a key factor at the structural design stage of large-span structures including footbridges, sport stadia, and high-rise buildings. As the structures tend to become slenderer and lighter, the mass of the crowd is not negligibly small compared with the mass of the structure. In such cases, the crowd and the structure form a coupling system through a mechanism known as human–structure interaction (HSI). Researchers found that the structural responses with and without HSI are different. However, the interaction effect on the structural responses has rarely been quantitatively evaluated from the perspective of human system parameters. In this paper, a novel method using a physical principle to predict jumping-induced structural responses is proposed, in which the structural response is expressed as the multiplication of a series of transfer functions representing human system and structural dynamic properties. Structural responses of a large-span concrete structure under jumping excitation are predicted using the proposed method and identified human system parameters. Comparison with measured responses shows satisfactory agreement. The proposed method provides a solution to consider HSI effect on the calculation of structural responses in the vibration serviceability design for large-span structures. [ABSTRACT FROM AUTHOR]