Elastoplastic Dynamic Time History Analysis Of Two-way Prestressed Concrete Space Frame

With the development of construction technology, prestressed concrete has been widely used in China. Prestressed concrete structure has the advantages of crack resistance and deformation recovery ability, etc. However, there are still some concerns about the seismic performance of prestressed concrete frame in high intensity area. At present, many studies about prestressed concrete component and plane frame have been done. But there are a few studies on the seismic performance of the two-way prestressed concrete space frame at home and abroad.In the paper, according to the current design code, 5 two-way prestressed concrete space frames including 1 frame of Grade 2 in intensity-category 7, 1 frame of Grade 2 in intensity-category 8 and 3 frames of Grade 1 in intensity-category 8 were designed in the same conditions of the structure plane layout and the vertical load etc. And The paper reduced the reinforcing bars of intorior columns of the frame of Grade 1 in intensity- category 8. Based on OpenSEES, this paper set up three-dimensional space models and input bidirectional earthquake waves to study the seismic behavior of the two-way prestressed concrete space frames through the dynamic time-history analysis under rare earthquake load. And the problem of the weakening the reinforcing bars of intorior columns of the frames of Grade 1 in intensity-category 8 was discussed. The comparison and analysis were made on seismic behavior of two-way and unidirectional prestressed concrete space frames. The main conclusions of this paper were as follows:(1)The global and local reactions of the two-way prestressed concrete space frames of Grade 2 in intensity-category 7 or 8 and Grade 1 in intensity-category 8 at the critical height(24m) and critical span(18m) could meet the requirements of the national criteria and achieve the target of “No Collapsing in the rare Earthquake”. the bearing capacity had considerable surplus.(2)The lateral displacement curve of the two-way prestressed concrete frames was shearing type. And The maximum inter-story displacement angle was at the level 1 or level 2. The energy dissipation mechanism of the two-way prestressed concrete frames was column hinge mechanism.(3)The energy dissipation mechanism of unidirectional prestressed frame was mixed energy dissipation with RC beam hinge mainly while in the RC frame direction was beam hinge mechanism and in the PC frame direction was column hinge mechanism. The hinge rate of prestressed beam and column of two-way prestressed concrete frames were larger than unidirectional prestressed frames in the PC frame direction.(4)Adopted the Huang Peng’s method of reducing reinforcement of intorior column, the rare seismic response of two-way prestressed concrete frames of Grade 1 in intensity-category 8 could fit the standard requirement. And this method could guide the plastic hinges to form at the end of the interior columns and reduce the rotation angle of side columns. But it couldn’t ensure the side columns don’t form plastic hinges.The main innovations of this paper were as follows:(1)The three-dimentional two-way prestressed concrete frame models were made to conduct the dynamic time history response on the two-direction seismic waves, and the response results were summarized.(2)The initial investigation on the interior column’s reinforcement of the two-way prestressed frame of Grade 1 intensity-category 8 was made. Comparison was made on influence on the column’s reinforcement between the “strong column weak beam” by the Huang Peng and the code. The seismic behavior of the two-way prestressed frame based on the weaken method by Huang Peng was investigated to make a foundation for the improvement of the midlle column’s reinforcement.