Abstract: The present disclosure provides a method for identifying modal parameters of engineering structures based on fast stochastic subspace identification, and relates to the field of structural modal parameters identification. The method includes the following steps: collecting responses; obtaining a unitary matrix by performing random projection on and QR decomposition of a matrix; obtaining a small matrix by projecting a Toeplitz matrix onto the unitary matrix; obtaining U, S, V matrices respectively by performing singular value decomposition of the small matrix; performing eigenvalue decomposition; and determining an order interval. According to the present disclosure, the small matrix is obtained through performing random projection on and QR decomposition of the traditional Toeplitz matrix, the dimensionality of the matrix by singular value decomposition is reduced and the computational efficiency of the matrix is improved.

Abstract: An intelligent method for efficiently classifying concrete cracks from large amounts of image data is proposed, named inverted residual (IR) 7-Efficient Channel Attention and Convolutional Block Attention Module (EC) network. The IR7-EC network consists of a convolutional layer, seven inverted residual-ECA structures, a CBAM attention mechanism, a pooling layer, and multiple fully connected layers that are sequentially connected. The inverted residual-ECA structure consists of two components: a depthwise separable convolution-based inverted residual structure and an ECA attention mechanism. The new inverted residual structure facilitates the feature extraction of concrete cracks. Compared to conventional network structures like VGG and Resnet, the proposed IR7-EC network excels in both accuracy and efficiency. Once the IR7-EC network is fully trained, it can accurately classify various types of concrete cracks in captured images.

Abstract: An evaluation method for corrosion damage evolution of underwater concrete structures includes performing the time reversal test on the concrete beam specimen placed in the water, performing the uniaxial compression test on the concrete cube specimens; immersing the concrete beam specimen and the concrete cube specimens in a hydrochloric acid solution, and performing the time reversal test on the concrete beam specimen on the 10th, 20th and 30th days respectively. At the same time, a concrete cube specimen is taken out to perform the uniaxial compression test on the 10th, 20th and 30th days respectively; and using the above calculation results to evaluate the corrosion evolution process thereof without damaging the underwater concrete structure.

Abstract: A damage identification method for a cantilever beam based on a multifractal spectrum of a multi-scale reconstructed attractor includes: acquiring an original acceleration signal of the cantilever beam by a dynamic measurement system, performing stationary wavelet decomposition on a pretreated acceleration signal to obtain multi-scale sub-signals, selecting the multi-scale sub-signal that can represent main vibration characteristics of the cantilever beam for phase space reconstruction and normalization to obtain a normalized multi-scale reconstructed attractor, constructing the multifractal spectrum of the multi-scale reconstructed attractor, establishing a damage index based on a singularity index of the multifractal spectrum, and identifying and locating damage of the cantilever beam according to a relative numerical value of the damage index.

Abstract: A cable tension calculation method simultaneously considering the sag, inclination angle and bending stiffness includes: querying basic parameters of a stay cable according to design data and construction data; considering influences of the sag, the inclination angle ? and the bending stiffness EI, to calculate dimensionless parameters ?, ? and ?2; testing an acceleration response of the stay cable by an acceleration sensor, to identify a frequency ? of the acceleration response of the stay cable, further calculating a dimensionless frequency {circumflex over (?)} of the stay cable and the dimensionless parameters ?, ? and ?2, and substituting the dimensionless frequency {circumflex over (?)} of the stay cable into a vibration characteristic equation, to establish a function relation between the dimensionless frequency {circumflex over (?)} and a cable tension H* of the stay cable; and solving a root of the vibration characteristic equation, and identifying the cable tension H* of the stay cable according to