Research On The Safety Evaluation Method And Key Technologies For Existing Space Latticed Structures

The application and development of space latticed structures in China has a history of several decades.Some existing space latticed structures may undergo structural degradation due to factors such as load action.Therefore,it is of great significance to evaluate the safety of structures.In the safety evaluation method of existing space latticed structures,how to select detection components and displacement measurement points from a large number of components and nodes,how to modify the structural model based on structural detection data,and how to evaluate and draw conclusions on the safety of the structure based on the detection data and damage model calculation results are key technical issues.This article conducts research on the above issues,as follows:A method for selecting detection components and displacement measurement points based on BP neural network is proposed.Using the displacement of structural nodes as the input and the damage degree of components and supports as the output,a BP neural network model is constructed.To reduce the output quantity of the BP neural network model,a substructure damage parameter is constructed as the output quantity.The selection principle of displacement measurement points is proposed,and in order to select detection components,a sensitivity analysis method is proposed to select displacement measurement points.Based on the prediction results of the BP neural network model and the component importance analysis,a method for selecting detection components is proposed considering the damage degree and importance of the components.A structural model modification method based on structural detection data is proposed.Based on a large number of existing studies,model modification methods for fractured and corroded components are proposed.Through axial compression simulation and post buckling loading and unloading simulation of typical components,it is concluded that the bended component has buckled and its post buckling loading and unloading performance is mastered.It is proposed to determine the maximum development degree of post buckling from the measured deflection and approximate axial force of the bended component,and then obtain its stress-strain curve.The average value of the slopes at each point of the curve is taken to obtain the reduced elastic modulus,and the bended component’s model is modified by reducing the elastic modulus.The midspan deflection of the bended component during buckling is used as the allowable deflection to evaluate the bending component,and a formula for calculating the allowable deflection is obtained by fitting based on axial compression simulation data.The measured node displacement is corrected by the node displacement of the initial model of the structure under dead load,and then the design coordinates of the node are corrected to complete the structural configuration correction.It is proposed to calculate the horizontal and vertical coordinates of unmeasured nodes using the regression analysis method and the vertical displacement of measured nodes,respectively.A comprehensive evaluation method for structural safety is proposed.Based on the specifications,various basic evaluation indicators for the component and the overall performance of the structure are constructed.The safety evaluation indicator system of existing space latticed structures is constructed based on the Analytic Hierarchy Process,and the weight coefficients of components are determined using the component importance coefficient ratio method,while the remaining weight coefficients are determined using the Analytic Hierarchy Process.The rating standards for all levels of evaluation indicators in the evaluation indicator system are established,and the fuzzy comprehensive evaluation method is mainly used for the comprehensive evaluation of structural safety.Finally,the safety evaluation method for existing space latticed structures was applied in the safety evaluation project of space grid structures of the natatorium of Zhejiang Sci-Tech University.