In this paper, based on the discrete particle model, the raindrop impact load correction formula is proposed. With the frequent occurrence of extreme weather, the rain load of structures under high wind speeds accompanied by heavy rainfall conditions has become a hot issue for research. The seismic response of this bridge type under multidimensional and multiangle excitation shows obvious superposition. The variation range of upper and lower rod axial force varies from 0.63 to 1.35 and from 0.81 to 1.51, respectively, the change trend of displacement in the X and Y directions is relatively consistent, the change of displacement in the Z direction is asynchronous, and the displacement of vault section increases by one time. Under the combined excitation of X + Y with a changing angle of 0°∼90°, the axial force variation of the chord at different positions and on the same section of the arch rib has spatial characteristics. The maximum axial force ratio of X + Y to X and Y is 2.1, the maximum axial force ratio of X + Y + Z (longitudinal) to X + Y, X + Z, and Y + Z is 1.4, 1.8, and 1.8 the displacement in X and Y direction under combined excitation is independent and the displacement in Z direction is its coupling term, but the displacement under X + Y + Z combined excitation is only 10% larger than that under X + Z and Y + Z combined excitation. With the increase of excitation dimensions, the value and relative ratio of chord axial force increase. The results show that the structure of long-span top-supported arch bridge extends in the longitudinal and vertical dimensions at the same time, and the mode shape density and mass distribution have multidirection and multiangle coupling. Then, the three-dimensional El Centro recorded wave after amplitude modulation is taken as the excitation wave the structural response under three kinds of single dimension and four kinds of multidimensional combined excitation and 0∼90° transformation X(longitudinal) + Y(transverse) orthogonal combined excitation is evaluated.
Taking a concrete-filled steel tube (CFST) arch bridge with a clear span of 400 m as an example, the in-depth analysis of its natural vibration characteristics is carried out by establishing a finite element model. The study results provide a theoretical basis for the damage diagnosis of the wood structure of ancient buildings along the traffic line. The function relation between the damage index and the damage degree is obtained to determine the structural damage degree. When SNR increases, the damage index will have an increasingly higher sensitivity and certain ability to resist the effect of noise. If SNR is 40 db or larger, the damage index can accurately identify the damage of ancient wooden structures. The results show that the wavelet packet energy curvature difference can decide the damage location of the middle part of the first-floor longitudinal beam, and the index value increases with the increase of damage degree. The wavelet packet energy curvature difference index was proposed to determine the structural damage location. The node acceleration response signals on beams were decomposed with a wavelet packet. Three-dimensional finite element model of the wood structure-foundation of the North House’s main hall in Tianshui under ground traffic excitation was established, and the damage of the first-floor longitudinal beam of the wood structure was simulated by the finite element method.
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