Research On Influence And Calculation For Moment Magnifying Coefficients At Column Ends Based On Beam Hinge Mechanism

In Chinese Aseismic Code, flexural bearing capacities of columns and beams aredifferent by means of moment augment factor of column. Further more, other aseismicmeasures work well in forming reasonableenergy dissipation mechanism. Research andpracticedemonstrate that the value of the capacity ratio is the key parameter forcontrolling structure’s response and forming reasonableenergy dissipation mechanism.“Strong column-weak beam” parameters of all kind of frame structures are amplified inearthquake resistant code(2010edition) comparing with the former one. The function ofthis parameter is to form beam hinge mechanism while structures are suffering largeearthquake, however, it is impossible to avoid the appearance of plastic pivot at ends ofcolumn.During large earthquake, the generation of ideal “beam hinge mechanism”, whichmeans there is no plastic pivot at ends of column,request various the capacity ratio fordifferent kind of frame structures, and the authentic the capacity ratio is the subjectinvestigated here. In this paper, a series oftypical plane frames located in5kind ofareas(7degree0.1g,7degree0.15g,8degree0.2g,8degree0.3g, and9degree0.4g)are designed following seismic design code(2010edition) and concrete structure designcode(2011edition). In these nonlinear response models, reinforcements in columns areprevented to reach yield point under large earthquake, and other materials are same asnormal ones. The area of longitudinal reinforcements is obtained based on the structuralinternal force and response level, and the real requirement of adjustment coefficient arecalculated for equation6.2.2-1and6.2.2-1in seismic design code(2010edition).Considering the randomicity of earthquake waves,30earthquake waves inputs areselected in the calculation of every frame. Based on the summary of the datadistribution and statistical results of all models, the suggested value the capacity ratiofor each seismic area is provided. For the purpose of verifying the suggested value, anew frame is design by using the value, and a nonlinear response analysis is run underlarge earth quake. By investigating the response of the whole and the part of the frame,the reliability of suggested value is verified.The following conclusions are obtained due to the works mentioned above:①After the adjustment of moment at column ends according equation6.2.2-1inseismic design code, amplification factors for interior joint and exterior joint is different: the later one is smaller than former one. The parameterη cfor interior joint increaseswith the raise of building height, and this phenomenon is more conspicuously in lowseismic intensity area. As a result of that, a single parameter can not meet the demandfor all parts of structures.②During the designing, negative moment area is always distributed in both endsof beam when the seismic intensity is low, and∑Mbis relative small for interior joint.Although the existingmoment augment factor of column according equation6.2.2-1isobviously differ from1.3, aseismic measures such as minimum reinforcement ratiooften cover up this insufficient.③In this paper, the capacity ratio of moment at column ends is adjustedbypracticalflexural capacity, amplification factors in exterior joint is close to the one forinterior joint. What is more, this method is not sensitive with the variation of buildingheight and distribution of floor bar, and it has a better controlling for exiting methodwhich is based on bending momentdesign value of beam.