Researches On The Underpinning Technology Of Building Structures

In order that old buildings meet people's new use requirements, they usually need to be reconstructed to increase useable space. When the underpinning technology of building structure is applied to reconstruction work for extending span, only a small part of columns and load-bearing walls need to be removed and the rest of structural members is barely affected, moreover, the other parts of the reconstructed buildings can be used normally in reconstruction period. For these reasons, more and more building reconstruction engineering begins to use the technology. However, when the underpinning technology is used, the internal force of original structure will take place big changes and the technology is quite complex. If we can't use it properly, then the structural members are likely to crack or the building may even collapse, therefore, it is very necessary for us to further study all kinds of underpinning technology in order that the underpinning reconstruction of buildings can be implemented successfully.The dissertation has made a systemic study and summarization on the underpinning technology of bent frame structure, masonry structure, frame structure and foundation .The main contents are as follows:(1) As far as each existing underpinning technology is concerned, its construction method, technical characteristics and application range has been summarized in the dissertation.(2) The author puts forward reacting force bracket underpinning technology applied to bent frame structure.(3) Aiming at bent frame structure, the author puts forward supportless underpinning technology with external prestress based on structure member strengthening method with external prestress. The technology improves the existing supportless underpinning technology.(4) In the dissertation, the design principles of underpinning technology for frame structure are stated amply. Aiming at internal-supporting underpinning technology for frame structure, when frame structures bear vertical load, the paper puts forward a calculation method of internal force.(5) As a result of research, the author puts forward increasing supporting-point underpinning technology. It recurs to prestressing bars to remove axial pressure borne by columns. After the axial pressure is unloaded, diagonal braces will be installed. After columns are removed, prestressing bars, diagonal braces and reconstructed frame structure will bear load together. As the help of prestressing bars and diagonal braces, the deformation of reconstructed frame structure will be very small.