| Composite structural system composed by Steel Reinforced Concrete (SRC) or Concrete Filled Tube (CFT) frame with Reinforced Concrete core is a new type of structural option, which was rapidly developed in the design of high-rise and super high-rise buildings in China in recent years. In view of its significant advantages, such as decreasing the overall cost, reducing the component section, speeding up the progress of construction and etc, this structural system attracted extensive attention from the engineering field to the investor.As the concrete core generally occupies the main part of the stiffness of the total system, the plastic hinge will occur firstly among the concrete core when the structure is subjected to rarly earthquake and cause degeneration of total stiffness. Thus the external steel frame will be suffered damage or even collapse caused by the redistribution of the seismic force. Therefore the frame shall be distributed more shear force in the stage of elastic design. The study and research for this type of structural system has been carried on in Chinese engineering field in recent years. Some progress have been achieved to some extent, but it not be very deep, especially the practical design experience base on the Chinese code for the super high-rise composite structure in the high seismic zone is still very infrequent. At present, many of the super high-rise buildings around 150m to 200m height or even above 300m height in China adopt composite structure, but these buildings were basically built in the zone of intensity 7. According to the Chinese code JGJ3-2002, maximal applicable height for the building adopting composite system made up of SRC external frame and RC core is 150m for the zone of intensity 8, where the main part of as-built composite buidings are generally lower than this limit at present, and the highest one is not more than 200m as well.This article takes the project of Beijing Fortune Plaza 2 Office Tower, the current highest composite building exceeding code in intensity 8 of China, as the practical example, systematical summary and study are base on the author's work during the project scheme and preliminary design, feasibility study for exceeding code limit and the series of seismic measures. The research work mainly focus on the structural system and member selection, second seismic defense line for perimeter frame design, seismic performance based design, the elastic and elasto-plastic time history analysis and so on. The author of this dissertation, as the projiect engineer and primary designer, has specifically responsible for a series of analysis and study work during the project preliminary design, feasibility study for code exceeding design, structural optimization design, and design review for construction design. Measures and suggestions are given in this artical for the composite design in high seismic zone base on the intensive analysis and study for the key technology.The Beijing Fortune Plaza 2 office tower, with 264m tall, will become the second tallest building after the China World Trade Centre 3A mage tower in Beijing as intensity 8 seismic zone and the tallest building adopting composite structural system composed by steel reinforced concrete frame and concrete core, which exceeds the Chinese code limit by 114m or 76%. The length-to-width ratio is close to 1.5, but unfavorable influence caused by torsional effect is successfully reduced by a rational control on the structural layout. Four strengthened-stories with outriggers and belt trusses are installed to provide additional lateral strength. Composite Steel Plate Wall (CSPW) is adopted in the lower level of the core to increase the lateral stiffness and enhance seismic performance effectively, at the same time reduces the self weight with thinner wall as well. Seismic performance based concept was overall embodied in the structural design. Large diameter circle Concrete Filled Tube (CFT) column is used in the perimeter frame along overall height, thus greatly reduce the section size and the amount of steel consumption. Base on the elastic and elasto-plastic time history analysis, the effective measures are taken to resist the significant influence from whiplash effect for the tall and slender structure caused by high order models, thus enhanced the structural safety. The seismic design of the tower has satisfied the additional requirements by expert review panel based on the general Chinese seismic codes. The structural scheme and member selection reflect comprehensive economic advantages in aspect of steel tonnage, fire proof and wind comfort, etc. thus, decrease the construction cost successfully. |
PDF Full Text Request