Seismic Study Of Existing Masonry Structure On Extension-Story-Adding Renovations

With the development of city construction,multi-storied brick buildings constructed in the 1980’s massively can’t meet the demands of function application.at the same time,the limited economic ability and land resource in present stage impede the demolition and reconstruction work.So storey-adding to these buildings has significant social and economic benefits. Especially to the longer multi-layer brick houses, bearing ability is limited, so the extension-storey-adding is widely used.Extension-storey-adding reform is divided further into disunion type and union type,the Integral type connect the old buildinngs with newly added frames, in order to increase extension ground floor’s stiffness and reduce the column’s effective length factor. And then it can improve the structure of the integrity and stiffness uniformity, the earthquake resistant ability has also been raised greatly. The transfer structure is successfully applied to extension-story engineering of building in order to ensure the security of new added structure ’s load transfer. More research on its stress performance and overall seismic performance is significant. At present, The integral storey adding is not explicit in force transmission and the connections have some effection on the seismic behaviour. To these questions, we need further study. This paper based on the actual engineering using "axillary-adding wall"transfer structure, studies the seismic performance of the whole structure and the effects on the extisting building. Using SAP2000 to research both the old masonry structure and the new structure after extension-storey-adding reform.Fristly the momen、shear force and the stress distribution are analysed to know the concrete filled steel tube have enough bearing capacity and have a good anti-seismic capacity, ensuring connections between the old and new structure will not damage prematurely, and then keep the safety of the whole structure. Then researching the vibration characteristics of the structure before and after storey adding, the flexibility become higher and the period become longer after storey adding reform, so it meets the actual structure property. Thirdly elastic time-history analysis were conducted to analyse the inter-layer stresses、layer-displacement and torsion angle comparatively.The results of studies show, after extension-storey-adding reform, the new adding frame using "axillary-adding wall "transfer structure distributes of stress more uniformity and effectively reduce the beams’ section height, so it not only increase the use of space, but also increase the extension adding frame of the lateral stiffness; the maximum lateral displacement、interstory drift and the inter-layer stresses increase obviously, so effective earthquake-resistant improvement measures are needed; maximal accelerations in erery storey decrease significantly, then the new adding part have obviously limite to the acceleration factor; using the concrete filled steel tube pined in one side and fixed in another as combination of the young and old structure is most lucrative.