189W activities were produced via the 192Os(n, α) reaction using irradiation of isotopically enriched 192Os metallic powder of ～100 mg/cm2 with 14 MeV neutrons. The X-γ and γ-γ coincidence measurements were made ...189W activities were produced via the 192Os(n, α) reaction using irradiation of isotopically enriched 192Os metallic powder of ～100 mg/cm2 with 14 MeV neutrons. The X-γ and γ-γ coincidence measurements were made so as to obtain γ rays from 189W decay and its coincidence relations. A new simple decay scheme of 189W including three γ rays of 210.2, 229.6 and 260.2 keV is proposed. Two new levels of 189Re at 470.4 and 489.8 keV are assigned.展开更多
Once a column in building is removed due to gas explosion,vehicle impact,terrorist attack,earthquake or any natural disaster,the loading supported by removed column transfers to neighboring structural elements.If thes...Once a column in building is removed due to gas explosion,vehicle impact,terrorist attack,earthquake or any natural disaster,the loading supported by removed column transfers to neighboring structural elements.If these elements are unable to resist the supplementary loading,they continue to fail,which leads to progressive collapse of building.In this paper,an efficient strategy to model and simulate the progressive collapse of multi-story reinforced concrete structure under sudden column removal is presented.The strategy is subdivided into several connected steps including failure mechanism creation,MBS dynamic analysis and dynamic contact simulation,the latter is solved by using conserving/decaying scheme to handle the stiff nonlinear dynamic equations.The effect of gravity loads,structure-ground contact,and structure-structure contact are accounted for as well.The main novelty in this study consists in the introduction of failure function,and the proper manner to control the mechanism creation of a frame until its total failure.Moreover,this contribution pertains to a very thorough investigation of progressive collapse of the structure under sudden column removal.The proposed methodology is applied to a six-story frame,and many different progressive collapse scenarios are investigated.The results ilustrate the efficiency of the proposed strategy.展开更多
基金Supported by National Science Foundation of China (10575118) and Chinese Academy of Sciences
文摘189W activities were produced via the 192Os(n, α) reaction using irradiation of isotopically enriched 192Os metallic powder of ～100 mg/cm2 with 14 MeV neutrons. The X-γ and γ-γ coincidence measurements were made so as to obtain γ rays from 189W decay and its coincidence relations. A new simple decay scheme of 189W including three γ rays of 210.2, 229.6 and 260.2 keV is proposed. Two new levels of 189Re at 470.4 and 489.8 keV are assigned.
文摘Once a column in building is removed due to gas explosion,vehicle impact,terrorist attack,earthquake or any natural disaster,the loading supported by removed column transfers to neighboring structural elements.If these elements are unable to resist the supplementary loading,they continue to fail,which leads to progressive collapse of building.In this paper,an efficient strategy to model and simulate the progressive collapse of multi-story reinforced concrete structure under sudden column removal is presented.The strategy is subdivided into several connected steps including failure mechanism creation,MBS dynamic analysis and dynamic contact simulation,the latter is solved by using conserving/decaying scheme to handle the stiff nonlinear dynamic equations.The effect of gravity loads,structure-ground contact,and structure-structure contact are accounted for as well.The main novelty in this study consists in the introduction of failure function,and the proper manner to control the mechanism creation of a frame until its total failure.Moreover,this contribution pertains to a very thorough investigation of progressive collapse of the structure under sudden column removal.The proposed methodology is applied to a six-story frame,and many different progressive collapse scenarios are investigated.The results ilustrate the efficiency of the proposed strategy.
