Viscoelastic artificial boundary elements are one of the most commonly used artificial boundaries when solving dynamic soil-structure interactions or near-field wave propagation problems. However, due to the lack of clear and practical stability criteria for the explicit algorithm that considers the influence of viscoelastic artificial boundary elements, the determination of the stable time increment in such numerical analyses is still a challenge. In this study, we proposed a numerical stability analysis method for the explicit algorithm with a 3D viscoelastic artificial boundary element based on the idea of a subsystem. Through this method, the artificial boundary subsystem that controls the stability of the overall numerical system is determined, and the analytical solution for the stability condition of the explicit integration algorithm with 3D viscoelastic artificial boundary elements is obtained. On this basis, the maximum time increment for solving dynamic problems with viscoelastic artificial boundary elements can be determined.
In order to improve the explosion resistance performance of masonry structures during the terrorist attacks and accidental disasters, clay brick and concrete block walls are reinforced by modified polyurea materials. Explosion resistance tests of these two kinds of masonry wall structures are carried out to analyze the failure modes and anti-explosion effects of reinforced masonry walls under different thickness and reinforcement modes. The results show that modified polyurea elastomer not only has good spraying adhesion and compatibility with the base material surface, but also can effectively encapsulate the explosive debris generated by the back blasting surface of the masonry wall under explosive load, which reduces the deformation and displacement of the wall.
Improving the survival probability of important ground facilities requires setting protective measures above ground with the development of precision guided weapons. For low altitude protection, a suitable detection system for a given velocity of target is a must. A special detection system fulfilling the requirements for protection was constructed based on multiUAVs coupled with radar device to track the coming target in this work. The target’s motion model was built as a function of signal arrival time, which was obtained from the objective function. To achieve better stability and tracking performance., an optimization method was presented according to the arrangement of detection system and parameters of the target, by minimizing the bias between the system centre and target position. It was found that effective tracking was achieved for the non-cooperative target with following control taken into consideration.
In order to reveal the influence law of explosion load when new subway under-crossing existing subway, the research with the method of combining theoretical calculation and numerical simulation was developed. With theoretical calculation method, the reasonable structural parameters and material parameters were chose, then the equivalent static load of under-crossing structure was obtained at the condition of explosion wave. By using the ANASYS/LS-DYNA software, the propagation law of explosion wave and the load change law of structure were simulated in four different models. Through comparison analysis, it showed the theoretical calculation method and numerical simulation method were rational, and the influence that existing subway on new under-crossing subway was only about the explosion wave propagation velocity except the explosion wave form and amplitude value, and the influence that new under-crossing subway on existing subway about explosion wave was very small. It provided a theoretical basis for design and construction for new under-crossing subway.
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