Progressive Collapse Resistance Performance Of Steel Storage Racks Under Forklift Truck Impact

Under the good macro-economic background,the demand of the warehousing industry in China continues to grow.Especially under the guidance of the concept of "Internet + Efficiency logistics",how to effectively improve the security of storage structure has gradually become the focus of the industry.As a widely used product in the assembled racking structure,multilayer steel racks need to use forklifts frequently when they send or fetch the goods.The accidental impact of forklift may lead to progressive collapse of steel shelves,which will endanger personal safety and property loss.However,the provisions about anti-progressive collapse in domestic and foreign design specifications are not applicable to steel racking structures,and the related research results are still rare.Therefore,the failure mechanism and dynamic response of progressive collapse of steel racking structure under the impact of forklift truck were studied in this paper,and the anti-collapse scheme was given.Firstly,the analysis method of progressive collapse of structures and the criterion of failure of structures are introduced and determined in this paper.On this basis,the main process of numerical simulation in this paper is determined.At the same time,based on the conservation of momentum and energy in Newton Classical Mechanics,a brief elastic collision theoretical analysis about the process of truck impact racks is carried out.Then,on the basis of the reasonable analysis method,the accurate and refined steel rack model and the new simplified forklift model are established.Based on the push-over test of frame-truss steel rack structure finished by our Research Group,the corresponding finite element model of nonlinear mutli-scale and high-efficient nonlinear member system of the steel rack were established,and the numerical simulation results with the test results were compared,and the accuracy of the finite element model of mutli-scale and member system of the steel rack and the rationality of the connector element used in the model were verified.At the same time,the calculation accuracy and efficiency of multi-scale finite element model and member system finite element model were compared,and the modeling method used in finite element simulation in this paper was determined.Besides,based on the static and dynamic test of the forklift truck finished by Benoit P.Gilbert,a new simplified model of forklift truck is proposed,which considers the impact of the forklift on the steel storage racks along aisle.The finite element model is established and the test results are compared,and the effectiveness of the new simplified model of forklift is verified.Thirdly,on the basis of the reasonable method of progressive collapse analysis and the accurate and effective modeling method and forklift model,the parameterized analysis was carried out.The factors of parametric analysis include: impact direction,impact velocity,horizontal position of column,mass of loaded cargo and impact height.The failure collapse mechanism and dynamic response of steel rack structure under the impact of forklift truck were revealed.The dynamic response obtained by forklift collision analysis is compared with the results obtained by the static analysis method of anti-progressive collapse in foreign codes.It is found that the static analysis method of anti-progressive collapse in the code is not safe.The main reason is that the load combination form of collapse analysis in code is not suitable for steel shelf structure.The results show that the impact response of steel rack has little differences due to different impact direction,and it is positively correlated with the impact velocity of forklift truck.Compared to the impact corner column of steel rack,the impact side column has greater dynamic response to the steel rack.The dynamic response of steel racks is less affected the mass of the cargo loaded by the forklift truck.The impact force is smaller but the peak displacement is larger in the region with weak lateral impact stiffness.Finally,two kinds of anti-collapse schemes are proposed based on the assembled steel shelves in parameterized analysis.They are the use of shock isolation bearing and the adjustment of diagnal bracing and row spacer short beam.Finite element modeling and calculation are carried out for the adjusted structure of the two schemes,and the validity of the two schemes was verified.At the same time,from the whole life cycle of the assembled steel racks,the corresponding anti-collapse measures are put forward for the design,manufacture,installation and later operation and maintenance of the steel rack structure.