Comparison Of Strong Column Weak Beam Failure Mechanism Of Reinforced Concrete Structure And Its Improvment

In Wenchuan earthquake, the damage to multistory frame structure is mainly caused by the failure of vertical component, leading to the local structure collapse. In this case, it is really serious that the hinge at column end fail earlier than that of beam, which is also contrary to the seismic design concept in Chinese code and causing concern to researchers and designers. In this paper,Comparing Chinese code, New Zealand’s code and Japanese code, analyze about the similarities and differences and the actual effect of strong column weak beam failure mechanism, then improve the Chinese seismic design detail.Comparing the norms of assurance measures of strong column weak beam mechanism in Chinese code, New Zealand’s code and Japanese code, which is mainly about internal force adjustment measures and construction measures,Analyze the similarities and differences and its strictness in theory. After analysis, internal force adjustment measures in New Zealand’s code is essential to that in Chinese code. But its moment magnification factor of column is more conservative. Internal force adjustment measures in Japanese code combines directly with design under rarely earthquake, preferably ensuring the effect of strong column weak beam failure mechanism. For construction measures, norms in New Zealand’s code and Japanese code are overall closed to that of first class and second class seismic degree frame structure in Chinese code.Through the use different internal force adjustment in Chinese code, New Zealand’s code Japanese code, adjust the frame structure example and then carry out dynamic elasto-plastic analysis and compare the strictness of three different kinds of internal force adjustment for controlling the strong column weak beam failure mechanism. By comparison, the frame structure which is controlled by the internal force adjustment method in Chinese code is destroyed as hybrid mechanism of beam hinge and column hinge. While the structures controlled by internal force adjustment measures in New Zealand’s code sand Japanese code are destroyed as the mechanism of the beam hinge.Based on the difference of the actual failure mechanism of structure by different internal force adjustment method, there reflects the demand forimproving the moment magnification factor in Chinese code. Under the premise of considering the line stiffness ratio of beam and column or not, concerning six different seismic fortification intensity and four different seismic class frame structure, carry out dynamic elasto-plastic analysis and observe its effect of strong column weak beam failure mechanism under different value of moment magnification factor. Through analysis, except the forth seismic class frame structure under six degrees(0.05g) fortification intensity and the first seismic class under nine degree(0.4g) fortification intensity adjusted by ∑Mc=1.2∑Mbua in Chinese code, the moment magnification factor of column of other frame structure in other fortification intensity need to be increased. Under the premise of considering the line stiffness ratio of beam to column, the strong column weak beam failure mechanism can be guaranteed according to the moment magnification factor of column in Chinese code.