Structural System Identification Of Single-tower Cable-stayed Bridge With Wide Box Girder Basing Observability Technology

With the development of China’s transportation economy,the traffic volume of large and medium-sized cities increased rapidly.The single pylon cable stayed bridge with wide box beams will be the mainstream design concept for middle span bridge,to the utilization efficiency of channel resources,as well as the aesthetics.However,the shear deformation of this type of structure,especially the shear lag effect,was more notable than that of the "narrow beam bridge".Proper consideration should be given to the shear lag effect in the field of health monitoring,otherwise,it would cause a series of system parameter prediction errors and reduce the actual effectiveness of the health assessment.This paper proposed a method for identifying the structural system of a wide box girder single-pylon cable-stayed bridge based on observed data and two-dimensional beam element stiffness matrix.This method uses a combination of observability technology,plane finite bar element and the analytical theory of the shear lag effect of the wide box girder,to establish a process for identifying parameters such as the axial stiffness of the cable,the bending stiffness of the main beam,and the warping to moment of inertia.Subsequently,the experimental model of continuous beams and corresponding data in the literature were cited to verify the feasibility of the method in this article,in which three identification conditions was set,included not considering shear deformation,considering the shear coefficient of the overall shear section of the section,and the identification method of structural system with additional displacement considering shear lag effect,to illustrate the feasibility of this method.An example study of a single-pylon cable-stayed bridge with wide box girder was used to compare the method proposed in this paper with two others structural system identification method,which mentioned in the feasibility test.The identification results of structural parameters indicated that compared with the identification error of EA and EI by the method of considering shear deformation by shear coefficient,the proposed method can reduce the overall identification error of EA by about 10%;reduced by about 5%,the recognition error from mid-span to the end of the main beam can be reduced by about 20%.This paper set a series of height-to-width ratio for the section,and substituting the obtained structural material parameters into the finite element model to study the sensitivity of different methods to section width.Finally,the results showed that the method proposed in this paper had better adaptability to section width than the structural system identification method considered shear deformation with shear coefficients.