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In order to study the influence of shape memory alloy (SMA) on the seismic response of railway self-centering piers, the SMA restrainer element is added to the verified two-spring model. Taking a railway bridge pier as the engineering background, the numerical analysis model is established based on OpenSees platform. By inputting three strong earthquake records, the influence of SMA restrainer on the pier is analyzed by nonlinear time history analysis method. The influence of the initial clearance and the change of the initial prestress of the key parameters of the SMA restrainer device on the displacement of the pier top and the bending moment of the pier bottom is discussed, and compared with the prestressed reinforcement restrainer. The results show that under ordinary ground motion El-Centro and Taft waves, the displacement at the top of the self-centering pier decreases with the decrease of the initial gap δ of the restrainer device, and the bending moment at the bottom of the pier increases with the decrease of the initial gap δ. With the increase of the initial preload of the SMA restrainer, the displacement of the top of the self-centering pier decreases and the bending moment of the bottom of the pier increases. The influence of SMA restrainer on the seismic response of self-centering piers under near-fault ground motion Northridge is complex. Under three strong earthquake records, compared with the prestressed reinforcement restrainer, SMA restrainer will reduce the bending moment of the pier bottom and increase the horizontal displacement of the pier top. [ABSTRACT FROM AUTHOR]

The influence of offset crack on dynamic impact fracture behavior is studied using the digital-leaser dynamic caustics system in conjunction with impact loading device. An inner mother crack along loading direction and its offset edge crack in PMMA were employed. The initiation and propagation behavior, as well as the caustics patterns of both cracks are observed. Some important dynamic fracture parameters of mother crack, such as the initiation time, maximum speed and dynamic stress intensity factor, are analyzed with different offset distance. The results show that the radio of crack spacing to crack offset distance is virtually important to the initiation time and maximum speed of mother crack, which are also influenced by the location of both cracks in the midline of the specimen. Moreover, the changes of dynamic intensity factor of mother cracks with different crack spacing are found to be similar, while the time of their maximum values are quite different.