| The moment modulation method is one kind of the design method for reinforced concrete continuous beams and frames considering redistribution of internal forces,which has been used for many years.The correlative codes and specifications all give provisions about it,but they are different from each other.To solve this problem,the analysis as follows have been finished:(1) According to the provisions of the Code for Seismic Design of Buildings (GB50011-2001),the beam fails before the column for a RC plane frame structure in zones of Earthquake Intensity 9. Based on the limit state of bearing capacity, a single-story and singl-span plane frame model is build to simulate the failure of RC plane frame structure under earthquake action.The structural analysis shows that the moment modulation method decreases the bearing capacity of plane frame structure. Furthermore, the rationality of moment modulation is discussed in the aspect of ductility, energy dissipation capacity,seismic performance,etc. The result shows that moment modulation would be disadvantageous to the seismic perfor-mance of RC plane frame structure.So the moment modulation method should not be used for plane frame structure in zones of Earthquake Intensity 9.(2)The design based on plane frame model for 3D frame always forms a strong-bean and weak-column RC plane frame structure.To clear about why this happen,several factors that influence the failure form of frame are studyed,such as slab,3D effect, overstrength of materials, the column moment amplification factor,etc. According to the comparison and the fruits the academe has achived,we can have a conclusion that the failue mode in zones of Earthquake Intensity 9 is "strong bean,weak column".so,when the 3D frame is simplified to a plane frame,,the moment modulation method should not be used in zones of Earthquake Intensity 9.(3)At present,the PKPM is widely used in structural design.Based on the conclusions above, a suggestion is given to optimize the PK programme. |
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