Propagation Law And Overpressure Load Of Blast Wave In Urban Complex Environment

Since"9.11", people are more and more concentrated on the problem of security. With the progress of social civilization and the development of economy, the scale of cities is larger and larger with the density of population bigger and bigger. Once the sudden and unexpected explosive events happen in such an urban complex environment, it will bring extremely severe consequences to the security of urban citizens and the city public finances. Therefore, damage assessment and mitigation of structures in complex urban environment to explosive loads has become one of the most important scientific programs of the country.Aiming at the complex environment in the urban, this paper analyzes the propagation law and the overpressure loads of blast wave with the ALE method using the LSDYNA3D soft, based on the theory of hydrokinetics and explosion mechanics. And it also analyzes the shadowing mechanism and proofing effects of an explosion-proof wall model for the blast wave. Mostly, the primary works include three sections:(1) A two-building model is established, compared with one-building model, to analyze and explicate the shadowing effect for the blast wave by the border buildings, and to analyze the reflecting effect for the blast wave between the buildings and the second impulse effects.(2) A typical T-style street model is established to simulate the complex environment. Compared with the simple environment, at the first, this paper analyzes the propagation law of the blast wave in the T-style street; and secondly it analyzes how the key parameters of the street such as the scaled distance and the scaled height and so on affect the overpressure loads evoked by the blast wave; and finally it analyzes distribution of the peak overpressure loads along the target building vertically.(3) Aiming at the impulse effects of the blast wave, an explosion-proof wall model is established to study the propagation law of the blast wave when there are some explosion-proof walls in front. At the same time, the shadowing mechanism and the proofing effects of the explosion-proof walls are analyzed as well.According to the works above, some main conclusions are drawn as follows: the blast wave can either be shadowing by other buildings or can be enhanced due to the presence of other buildings in an urban environment; In an urban environment, the blast wave includes two phases: the positive overpressure phase and the negative overpressure phase. The peak positive overpressure evoked by the blast wave in the complex environment is about 5-6 times as more as it in the simple environment, however, it lasts a quite short time. In the contrary, the negative phase lasts a longer time, although its peak overpressure is lower; The key parameters of the street such as the scaled distance and the scaled height and so on affect the overpressure loads evoked by the blast wave a lot; the explosion-proof walls show a good performance that they can block the blast wave effetely and can decrease the peak overpressure loads a lot.