Abstract:The paper presents the theory of Hamilton variation principle which is the current method for impact problem, central difference method which is efficient solution of finite element (FE) method for impact problem and adapts to solve non-linear dynamic problem. And it introduces the ANSYS/LS-DYNA which is the popular FE software for impact problem both at home and abroad. Then it gives solutions for one simple model by analytical method and ANSYS/LS-DYNA respectively to validate function of software, and they are consistent. Afterward, it gives model of singlelayer Kiewitt reticulated dome with a span of 60 m, and the cylinder impactor, and introduces the contact interface arithmetic, especially the material model of steel (piecewise linear plasticity model) which takes stain rate into account and makes steel failure stress higher under impact loads. The vertical displacement, stress in main members, and the plastic deformation for dome under impact loads were obtained. Then four failure modes (no failure, moderate failure, global failure and slight failure) were summarized according to the rules of dynamic response. And the characteristics of dynamic response for each failure mode were shown.The progressive collapse of the World Trade Center towers in the 9/11 incident, stimulates interests of researchers for investigating performance of important buildings under impact. Large space structures are such symbolic buildings of a city, usually with social and economic significance. However, the research on this kind of structures under unexpected impact has so far been little.Tan [1] conducted test study of means to strengthening floors in steel buildings to prevent progressive collapse. Xiong et al [2,3] extended the research to analyzing performance of steel structures with composite floors under impact loads. Their studies involved single-story buildings only. Lu and Jiang [4] simulated the progressive collapse of the World Trade Center towers by finite element (FE) method in the wake of the 9/11 incident. Zhao et al [5] investigated the damage of reinforced concrete structures supposed to be under impact of aircraft. However, published studies of the behavior of large space structures subjected to impact loads are few. Li and his team [6][7][8] investigated the dynamic response of single-layer Kiewitt reticulated dome under impact, and no failure dome appeared under the smaller impact loads.In this paper, the FE model of the single-layer Kiewitt reticulated dome with a span of 60 m and the FE model of impactor were developed. Numerical simulations of the behavior of single-layer Kiewitt reticulated dome under impact loads were conducted. Dynamic responses of single-layer Kiewitt reticulated dome, which contain the stress of main members, the vertical deformation, and the plastic deformation development, were given. Then four failure modes were summarized according to the dynamic responses. Moreover, it displayed the impact loads, stresses of R 1 and R 2 , and the vertical deformations of types 2-4 for wh...
Abstract:No failure, moderate failure, severe failure, and slight failure are the four failure modes generalized observed in the dynamic response of the single-layer reticulated dome under vertical impact load on apex. T E (the time that the end of impact force) and T F (the time that members are broken) are two key times in the failure process. Characteristics of dynamic responses at the two key times are shown in order to make the failure mechanism clear. Then three steps of energy transfer are summarized, i.e. energy applying, energy loss and energy transfer, energy consumption. Based on the three steps, energy transfer process for the failure reticulated dome under once impact is introduced. Energy transmissibility and local loss ratio are put forward firstly to obtain LF E (the energy left in the main reticulated dome) from the initial kinetic energy of impactor. Moreover, the distribution of failure modes is decided by LF E which leads to the maximum dynamic response of the reticulated dome, but not by the initial impact kinetic energy of impactor.
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