The Failure Mechanism Analysis Of The Concrete Frame Structure

The frame structure was widely used in various buildings in recent years. And the experts pay more and more attention to the seismic performance of frame structures. Chinese standard's design requirements for the framework is"strong column and weak beam", that is when the structure enters the plastic state, plastic hinges appear at the ends of beams, and have good ductility after post-yield. The structure will not collapse, and plastic deformation of structure can dissipate seismic energy.The data after the earthquake shows that the frame structures'response to the earthquake did not reach the expected requirement which is"strong column and weak beam". Most of the frame columns were damaged seriously. Some form plastic hinges at column ends and slope. Some occur interlayer lateral displacement, then lead to an overall collapse finally. While the frame beams'damage were lighter significantly.In order to study on structure's failure mechanism, this paper adopts Pushover analysis, introduces basic principle and process of Pushover analysis and SAP2000 finite element software. SAP2000 is powerful, that can meet requirement of the paper's research purpose.The reasons for the frame can not reach the strong column and weak beam requirement are :(1)over bar of the beam ends;(2)strengthening to the beams of cast-in-place floor ;(3)the minimum reinforcement ratio and the minimal stirrup ratio of the columns are small;(4)axial compression ratio of columns is large relatively. But the main reason is the requirement to the columns is not enough currently. The chapter three of this essay takes a actual building as an example, designs the structure according to our specifications strictly. Then it makes Pushover analysis by SAP2000 finite element analysis software, and gets the plastic development of the structure. Improve the structure in four aspects: The first , augmenting concrete strength grade of columns.; The second , increasing the moment magnifying factors at column ends; The third , enlarging steel strength grade of columns; The fourth,. This paper makes Pushover analysis and observes the plastic development of the structures. The result shows the first three methods are all effective, the fourth method is not very effective. Besides, the paper compared that methods on economic. Enlarging steel strength grade of columns is the cheapest, while increasing the area of column section is the most expensive. Enlarging steel strength grade of columns can be used under norms, and is economic and practical.Finally, because frame - shear wall structures'damage is lighter after earthquake, the main frame do not have serious damage, while some of the shear walls have cracks or collapses. The original structure was modified to frame - shear wall structure in the chapter four of this essay. The chapter four makes Pushover analysis on the frame - shear wall structure, observes the plastic development of the structure and studies on its seismic performance. The conclusion shows that the seismic performance of frame - shear wall is good, failure mechanism is reasonable, and can meet the design expectations.