Studies On The Performanced-Based Seismic Design Of Shanghai World Financial Center Tower

The theory of performance-based seismic design (PBSD) was proposed by American and Japanese researchers in the early 1990's, which is a milestone in the modern seismic design procedures. The objective of performance-based seismic design is to control structural damage, economic loss and casualties under designable extent, moreover, to maintain the buildings functional after earthquake.The height of 101-storey Shanghai World Financial Center Tower (SHWFC) is 492m above ground making it possible the tallest building in the world when completed, and its aspect ratio of height to width is 8.49. According to Technical specifications for concrete structures of tall building (JGJ3-2002), the height of the building clearly exceeds the stipulated maximum height of 190m for a composite frame/reinforced concrete core building. The aspect ratio also exceeds the stipulated limit of 7 for a basic seismic intensity of 7. Three parallel structural systems being composed of mega-structure, the reinforced concrete and braced steel services core and the outrigger trusses, are employed to resist lateral loads. The reinforced concrete consisting of lower core, middle core and upper core are not continuous vertically. Instead of providing braced frames at the exterior curved surfaces of the building, single-diagonal system is adopted on the vertical faces in the mega-structure frame.Considering the properties of site soil, the building functions and importance, the investment and profit, the seismic design objectives were firstly proposed. A series of experimental and analytical researches were carried on the SHWFC adopted the theory of performance-based seismic design to verify that the structural system meets the seismic design objectives. The main contests are as follows:A scaled model was made and tested on shaking table. The test was carried out in four phases representing frequent, basic and seldom occurrences of design intensity 7, and seldom occurrence of design intensity 8, respectively. 2-D waves of El Centro, San Fernando and 1-D wave of Shanghai artificial accelerogram (SHW2) were selected. The time scale was 1/11.18. After different series of ground acceleration were inputted, the white noise was scanned to determine the natural frequencies and the damping ratios of the model structure. According to the similitude law, dynamic characteristics and responses of the prototype structure were calculated. The experimental results demonstrate that the structural system meets the seismic design objectives.A finite element analysis was carded on SHWFC in the phases representing frequent, basic and seldom occurrences of design intensity 7 using the program of ANSYS. The analytical results were compared with the experimental ones to verify the accuracies. Dynamic characteristics, responses of the prototype structure and stress contour of R.C. core were obtained. The finite element analytical results demonstrate that the structural system meets the seismic design objectives.A nonlinear time history analysis was carried on the simplified structural system using TBNLDA, which was developed by State Key Laboratory for Disaster Reduction in Civil Engineering at Tongji University. The simplified model was composed of three parallel lateral resistant structural system and perimeter steel columns and beams were omitted. The analytical results were compared with ones from shaking table test. The prototype structure was analyzed to study its dynamic characteristics and responses under the different earthquakes of frequent, basic, seldom occurrences of design intensity 7 and seldom occurrences of design intensity 8. The nonlinear time history analytical results demonstrate that the structural system meets the seismic design objectives.The analytical and experimental results were adopted to Verify that the key joints at the connection of mega-column, mega diagonals and belt truss meet the seismic design objectives. Steel specimens and concrete specimens with steel embedded were tested by adopting cyclic reverse loads. Finite element software ANSYS was used to analyze the static stress and yielding distribution.A refined finite element analysis was made on transfer stories from floor 56 to floor 61 using sub-model functions of ANSYS. The characteristics of stress and displacement contours for transfer slabs and R. C. core were analyzed. The results show that the responses of transfer stories meet the seismic design objectives.Experimental and analytical studies verify and complement each other, and overall results demonstrate that SHWFC meets the seismic design objectives under different earthquake levels.