Study On Seismic Provisions For RC Seismic Design Category I Frame-wall And Frame-tube Structures Based On Nonlinear-Dynamic Analysis

Some seismic provisions of RC frame-wall dual systems and RC frame-tube dual systems in Chinese executive RC designed codes are enacted in accordance with the experiment results,earthquake-damage experiences and the practice art of engineering, and also involved some measures in foreign codes, so these provisions still have not been verified by theoretical analyses and actual earthquake action. Considered the realistic background, the task, that to validate and improve the availability of this seismic measures related the RC frame-wall & frame-tube dual systems, seems to be very important and significative. Therefore, five typical structures up to 60m and located in Intensity Region 8 were selected in this article(three frame-wall dual system and two frame-tube dual system), and designed exactly according to The Code for Design of Concrete Structures,The Code for Seismic Design of Buildings and The Technical Specification for Concrete Structures of Tall Building, after the design working to be complete, these nonlinear dynamic response analyses of corresponding structures imposed on rare earthquake are carried out in virtue of the nonlinear dynamic response analysis program FW-EPA, which is verified to be stable and credible. According to the analytical results, the related seismic criterions about upper structures in the Chinese codes have been identified.To attain these objectives , analyses in this article are conducted as following:①Five buildings were choosed and designed in term of the provisions prescribed by Chinese codes. A 30-story frame-wall structure located in Intensity Region 8(0.2g), two 24-story frame-wall structures located in Intensity Region 8(0.3g), and a 25-story frame-tube system located in Intensity Region 8(0.2g) and a 20-story frame-tube system located in Intensity Region 8(0.3g). Beside, two structures, selected from the upper three frame-wall systems, were designed in the manner, which is not to consider the 8.1.4 Provision of The JGJ3-2002. So the total structures is seven.②The acceleration-histories at rare earthquakes level were imposed separately to the seven structures and the nonlinear dynamic response analyses conducted. Afterward study every model's response behavior of the each history on the foundation of existed research conclusions, and mainly focus on the shearwall's seismic shear performance,the demand of ductility about coupled-beam,the performance of frame and the overstrength of the integer structures about the overturning-moment and shear aspect. From the evaluations and discussions of the results presented in this report, the main specific conclusions are given below:①Because the shearwall and tube of every structure exhibits better axial-flexural strength and nonlinear stiffness at the rare earthquake level, the total seismic performance seems to be fine.②The rotational ductility-demand of the coupling beams with different span to depth ratio have been identified, and find that the maximal ductility demand does not exceed to 3.0 in generally and the corresponding coupling-beam located below the middle of structure's height. Further research and find out the maximal story drift is the most direct parameter to affect the coupling beam's maximal ductility demand.③Because of the shearwall and tube exhibits better axial-flexural strength and nonlinear stiffness at the rare earthquake level, the earthquake load level acted on the frame of dual systems is low and the seismic provisions enhances greatly the flexural strength. Based on the two factors, the frame in the frame-shearwall system remains non-yield states. Therefore, it is advice that easing some seismic provisions related the frame moderately, even if the structure's height breaks though 60 meter.④Because of the shear-redistribution exceeding the compressed pier's shear level, dynamic effect and great flexural overstrength of structures, the shearwall appears probably the shear failing during the rare earthquake. So it is suggested to the code makers that the shear strength of wall should be enhanced to higher level.⑤According to the analytical results, it is found that the shear overstrength demand is higher than the flexural overstrength demand. And the great flexural overstrength has increased the globe stiffness, hence the actual increased response shear level exceeds the shear capacities of the walls, which is designed according to the design shear forces enhanced, there are certain risks of shear failures. Therefore, it is to remind the academe and engineer to pay attention to the use of the flexural overstrength.⑥From time-history curves of the story shear, the globe overturning moment,and the story displacements, it is discovered that the each story's response history is much more similar and postpositive, so the viewpoint is brought forward that the essence of each story response history is the earthquake wave spreads through the medium of reinforced concrete, so the all reactions possess of the features of wave.