Comparison Of Seismic Design Of RC Frame-core Tube Structure Between Chinese And American Codes

The frame-core tube structure is widely used in China and the United States.In this paper,a simplified frame-core tube structure is established to carry out seismic design in accordance with the Chinese and US codes under the condition of the same seismic hazard,same load,basically the same site conditions and basically the same material strength.By optimizing the two structures to the limit of the story drift as far as possible,the reinforcement of the two structures is obtained,and then the elasto-plastic analysis model is established to compare the seismic performance of the two structures.The main work and conclusions are as follows:(1)The relevant provisions on seismic design of frame-core tube structures in China and the United States are compared,and the seismic precautionary criterion,seismic design method,seismic action calculation,seismic calculation measures and structural measures of the two countries are analyzed and evaluated.(2)Take a simplified frame-core tube structure,and introduce how to build the model and conduct the seismic design according to the Chinese and US codes.The major differences are as follows: when building the model,the US scheme needs to reduce the bending stiffness of all components,while the Chinese scheme only needs to reduce the stiffness of the coupling beams.In the calculation of seismic action,the US scheme requires both response spectrum method and equivalent lateral force method,while the Chinese scheme only needs to use response spectrum method.Under the same component size,the base shear of the US model is smaller than that of the Chinese model,the story drift is larger than that of the Chinese model,and the frame shear ratios in dual system is smaller than that of the Chinese model.(3)Take the story drift as the objective to optimize the structure of the two schemes.The Chinese scheme controlled by torsional stiffness cannot be further optimized,while the US scheme controlled by strength cannot be further optimized.After optimization,the amount of concrete used of the beam and column in the US scheme is smaller than that in the Chinese scheme.The amount of column longitudinal reinforcement is smaller than that of the Chinese scheme,but the amount of stirrup is larger than that of the Chinese scheme.The amount of beam reinforcement is less than that of the Chinese scheme;Compared with the Chinese scheme,the amount of reinforcement of the shear wall constraint boundary element and the constraint scope is larger.The shear wall of the upper floor in Chinese scheme needs to set structural boundary member,while the US scheme does not need to set boundary element after calculation.(4)The elasto-plastic analysis model of two schemes was established in SAUSAGE and time history analysis was conducted.The results show that the yield sequence of the two structures is reasonable under the action of different seismic strength grades.Under the action of rare earthquake,the compression damage of beam members,bottom columns and bottom shear wall in the US scheme is lighter than that in the Chinese scheme,and the tensile plastic strain of constraint boundary element is less than that in the Chinese scheme.However,the compression damage of the upper shear wall of the US scheme is slightly heavier than that of the Chinese scheme.Both schemes meet the performance requirements of their respective codes under rare earthquakes and did not collapse.(5)The range of constraint boundary element and the reinforcement of the bottom shear wall of the US scheme are larger than the Chinese scheme,and the US scheme has strict requirements on the stirrups of beams,columns and the shear wall,which is worthy of Chinese code learning.The constraint range of the boundary element is fixed by Chinese code,the design process is simple,and the upper shear wall needs to set the structural boundary element.These practices are better and should be retained.When the structure is relatively soft and close to the story drift limit,the designer should be aware of strengthening the vertical reinforcement rate of the bottom shear wall to improve the seismic performance of the structure and prevent collapse.