The Technique Of Adding Extra-floors Spanning Existing Building With Steel Structure And Its Application

The technique of adding extra-floors spanning existing building with steel structure has many remarkable aspects on technology, economy and safety . In order to extend application of this new structure, this paper introduces its usual structural system, design procedures and initial analyses of seismic performance. Meanwhile this paper provides calculation methods combining with two study cases and proposes some new suggestion to optimize structural design compared with some existed projects. The contents are as follows:1. Correlative technique: From rational structural scheme perspective, the weaknesses of this structural system in designing are pointed out, the sound section types and the stabilization control measures of beams and columns are introduced. Finally, The foundation treatment projects of new and old buildings are put forward.2. The static analysis: combining with two study cases, and using ANSYS software, the static analysis is done for separated type and integral type coat framing. The key factors in structural design are brought forward through comparing the results and further optimized measures are advanced.3. The seismic analysis: According to the code for seismic design of building and combining with two study cases, The dynamic characteristics of adding extra-floors spanning existing building with steel structure are analyzed through making three-dimensional models, and the seismic responses of the separated and integral coat framing are obtained by using response spectrum method and time history analysis method, the results are compared and studied which can be served as the basic of such structure design.4. The application of base-isolation technology: Taking example for the separated type coat framing which adopted base-isolation technology, making the three-dimensional model, and importing the nonlinear characteristics of base-isolation bearings, the seismic responses under the horizontal earthquake are obtained by using elastic-plastic time history analysis method. And the results are compared with those of traditional earthquake-resistance design. That makes the initial research for extending the application of base-isolation technology in the structure of adding extra-floors spanning existing building.All the results described above make sense to develop the technique of adding extra-floors spanning existing building with steel structure and revise the anti-seismic theory and construction design.