Numerical Analysis And Research On Moving Load Identification Based On L-M Algorithm

Bridges are subjected to moving loads continuously during service.Accurate assessment of load-bearing status of bridge structures is an effective guarantee for structural safety in service.As an important branch of bridge health monitoring technology,moving load identification technology can help superintendents to understand the real stress state of bridge structure clearly,and provide important reference for maintenance and management decision of bridge structure.Previous studies mostly focus on the identification and analysis of moving loads for structures with certain parameters,but the uncertainties in structural parameters are not taken into account enough.However,in the process of bridge construction,manufacturing and installation errors are unavoidable,and structural parameters are easy to contain a certain degree of uncertainty.It is of great engineering value and theoretical significance to study the identification of moving loads combining the uncertainty of parameters.For the problem of moving load identification,the structural response analysis and load identification of simply supported beam and cable-stayed bridge are carried out respectively,and the method of uncertainty treatment combining uncertain parameters with fuzzy membership degree is constructed.The method takes into account the uncertainty of structural parameters comprehensively and is convenient to solve the upper and lower bounds of structural response intervals,thus providing a new idea for the identification of moving load intervals.The research work of this paper mainly includes the following aspects:1.For the structural model with certain parameters,the direct and inverse numerical model of moving load problem is constructed.On the basis of direct problem analysis of moving loads,combined with the L-M algorithm,a numerical analysis model for time-history identification of moving loads is constructed.Based on the numerical models of simply supported beam and cable-stayed bridge,the effects of load form,speed of load moving,load variation and noise level on the identification of moving loads of structures with certain parameters are discussed.In addition,the relevant numerical analysis program is written,and the interactive calculation and analysis between the program and the finite element software is realized.2.The direct numerical model of the moving load problem is constructed for the structural model with uncertain parameters.Based on the calculation model of simply supported beam and cable-stayed bridge,the uncertain parameters are fuzzified by the fuzzy theory,and the corresponding response intervals of different membership degrees are analyzed.The effect of different uncertain parameters on the structural response interval is compared and analyzed,and the influence of multiple uncertain parameters on the structural response interval is discussed.3.The numerical analysis of interval identification is carried out for the problem of moving load identification with uncertain parameters.Combining uncertainty analysis model and L-M algorithm,the identification model of moving load interval is constructed,and the identification of moving load interval of simply supported beam and cable-stayed bridge structures with uncertain parameters is carried out.The effects of different parameter types,load types and membership degrees of different fuzzy parameters on the identification effects of intervals are discussed respectively,the characteristics and the rules of identification effects are summarized.Through structural response analysis,load identification research,direct and inverse numerical analysis of uncertain problems for simply supported beam and cable-stayed bridge structures,the effect rules of relevant parameters on structural response and load identification interval are obtained.The relevant research idea and research results can provide important reference basis for the follow-up study of moving load identification.