| Talking about the earthquake is like talking about the tiger.The earthquake brought us a painful lesson.Ten years ago,the 8.0-magnitude WenChuan earthquake was still fresh in our memory.According to the investigations,most of the frame structures in the Wenchuan earthquake failed to appear in the form of structural destruction of"strong pillars and weak beams."On the contrary,the column hinge appeared before the beam hinge and gradually developed into destruction,that is the"strong beam weak column[2]"Fragile destruction,which led to the collapse of a large number of buildings,brought catastrophic losses to the people.According to the research,the ductility of RC frame structure"strong beam weak column"is much worse than that of"strong pillar weak beam".This paper is based on the Chinese,American and European standards for seismic design,combined with the formation mechanism of the RC frame structure"strong pillar weak beam".Several factors affecting the formation of"strong column and weak beam"are pointed out,such as the effect of cast-in-situ floor and its reinforcement,the axial pressure ratio,the reduction coefficient of seismic force,the reinforcement rate of the beam column,and the filling wall.In this paper,the in-situ floor plate and its reinforcement and frame girder are mainly studied.In order to improve the ductility reserve capacity of RC frame structure under rare earthquake,Pushover analysis of RC frame structure was carried out by SAP 2000,and the ductility reserve of the structural measures of"strong column weak beam"in seismic codes of China,the United States and Europe was studied.It is concluded that RC frame structure has the highest ductility reserve under the construction measures in the American ACI code under the rare earthquake conditions.The proposed values of increasing coefficient of bending moment of column end under different seismic level are given.The work accomplished in this paper is as follows:1.According to the ductility of the formation mechanism of"strong column and weak beam"of RC frame structure,this paper listed the construction measures related to Chinese building seismic design specification GB 50011-2010,American ACI and European Code specification with compared their implementation characteristics of"strong column and weak beam"of RC frame structure.In chapter 2,the theory of elastoplastic analysis is introduced.2.This paper use PKPM first with no considering the role of cast-in-place floor slab and steel rectangular section beams reinforcement calculation and elastic analysis.Combining SATEWE elastic calculation results and the reference to relevant literature of formula calculate by hand,the American norm?ACI?,Europe EC8 specification in the conversion effects of cast-in-place floor slab and steel pillars side bending moment increase coefficient[2].3.In this paper,the reinforcement of the RC frame column is recalculated based on the converted coefficient about moment increase of column end.It is assumed that the ideal RC frame simplification model is used.The finite element software SAP 2000 is used to analyze each model at 7 degrees?0.15 g?and 8 degrees?0.30 g?respectively.Pushover analysis.The energy dissipation mechanism and ductility reserve of RC framework structures in rare earthquakes in China,the United States,and Europe are studied by means of the basement shear force,displacement,time,sequence,development state,and damage degree of plastic hinge of beams and columns in each model.Based on the results of elastoplastic analysis,some suggestions are given for the increasing coefficient about the bending moment of the column end in our architectural design specification. |
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