Progressive Collapse Evaluation for Historic Building Structures

摘要

Important historic buildings may be subjected to accidental loads during their service life. It is therefore necessary not only to evaluate their safety under traditional loads and seismic action (only in earthquake area), but also to evaluate the structural performance of resisting progressive collapse. For historic buildings, two aspects make them different from the modern buildings: the material properties are usually deteriorated to some extent, and the structural system/constructions may not meet the requirements of current design and construction codes. Considering such aspects, a method consisting of four steps to evaluate the performance of the historic buildings to resist progressive collapse is presented in this paper. Firstly, the building layout should be evaluated whether it can protect the occupants from the possible explosion. Secondly, geometrical information, structural constructions and the material properties are to be investigated in details. Thirdly, by means of tie force method and the alternate path method the performance of the structure is analyzed to resist progressive collapse. The load combinations used in the analysis are derived based on the expected service life of the structure. The failure criteria for the structural elements as well as the damage limits for the structure follow the provisions addressed in American Unified Facilities Criteria “Design of Structure to Resist Progressive Collapse” (UFC 4-023-03). Finally, based on the above information an overall evaluation is made for the probably structural retrofitting and strengthening. This method is illustrated with a case study of a steel frame historic building, namely the Bund 18 building, in Shanghai, China. Some suggestions for retrofitting and strengthening this building are also presented.