Study Of The Response And Protective Methods Of Steel Structure With Composite Slab Under Impact Loads

The research about the response of important structures subjected to impact loads is a very difficult problem due to inter-disciplinary contributions, and also critical to the safety of countries. Since 1980's, a large number of important buildings through out the world have been destroyed by impact loads in terrorist attacks, from which "9.11"was the most catastrophic incident and cost many people's lives and millions of dollars. However, it also challenges the development of the prevention of progressive collapse. There are many very important structures that are the symbols of politics and economy in our country. Once the important structures are damaged by impact loads in terrorist attacks such as "9.11", the losses are huge. So how to study the response and improve some more effective methods to prevent the structure from collapsing is very urgent. The FE analysis of the response and protective methods of steel structure with composite slab subjected to impact loads is done using finite element program LS-DYNA and ABAQUS based on tests in this thesis. This analysis includes three parts: in the first part, it simulates the tests and the results of FE analysis show a great agreement with the results of test; in the second part, it gives the methods to make sure the key elements, and analyzes the the failure rule of the composite structure subjected to impact loads, then gives the formula of critical deflection of collapse using MATLAB; in the third part, it studies the protective methods to prevent the structure from collapsing according to different situations: when the impact loads act on the upper part, the key element is destroyed and the load path is changed, some members will not collapse because the external loads are small, but those members will generate big deflections, and the deflections will effect the fire resistance of members very much. In order to prevent the structure from collapsing, we must strengthen some local parts of the structure on the stage of design or increase the thickness of fire protection; when the impact loads act on the lower part, the key eement is destroyed, and the remained structure will collapse due to the excessive loads. In order to prevent the structure from collapsing, we can add some steel cables under some members to give some alternate load paths. Through the analysis of FEM, it is feasible and effective.