Preliminary Research On The Design Method Of Ppc Frame Structures Considering Secondary Axial Force

Partial prestressed concrete(PPC) frame structures have been widely used at home and abroad,but the research on secondary internal force and redistribution of it still have some remaining issues to solve,it is important to verify the Moment redistribution formula of our country’s code and research on the secondary axial force issues.The main contents of this paper are to design PPC frame structures according to the Moment redistribution formula stipulated in the code for design of concrete structures GB50010-2010,do nonlinear analysis with Open SEES.Based on the above analysis,verify the rationality of the Moment redistribution formula;research the affect of secondary internal force to the performance of PPC frame structures;analyze whether need to consider the affect of secondary axial force when designing prestressed concrete frames,and how to consider.The following are the major conclusions of this paper:①Design PPC frames according to the Moment redistribution formular of our country’s code and do analysis,the ultimate load,actural capacity of Moment redistribution,relative compressive zone height and ductility all can meet the requirements,verify the rationality of the Moment redistribution formula stipulated in the code for design of concrete structures.②Comparative analyze force performance of one-layer multispan PPC frames with secondary internal force and without secondary internal force,there are big diffrences in ultimate load and Moment redistribution ability,the model with secondary internal force can bear bigger ultimate load,and have bigger Moment redistribution ability.Comparative analyze load-axial force curves of the two models and show,before loading,the two models start with secondary axial force and zero respectively,the load-axial force curves move closer gradually,and to ultimate state,the difference drastically reduced.Comparative analyze load-Moment and Moment-curvature curves of the two models and show,before loading,the two models start with secondary Moment and zero respectively,to the same curvature,the former’s support section Moment is bigger than the latter’s,and to ultimate state,the former’s support section ultimate Moment is bigger than the latter’s too.③To commom multilayer and multispan PPC frames with the linear stiffness ratio of column and beam less than 10,when the axial compression ratio is more than-0.1(compression) or less than 0.05(tension),the affect of axial force to ultimate bending capacity on normal section can be neglected.④The PPC frames of The this paper all performance damage at support section of ground layer,with analysis,get the range of axial force redistribution preliminary:for single-layer frames,the ultimate axial force performances compression,when the ratio of secondary axial force and elastic axial force is within-0.2 to-0.35,the ultimate axial force is 1.0 to 1.1 times to elastic axial force;for multilayer frames,the ultimate axial force of ground layer performances tension,when the ratio of secondary axial force and elastic axial force is within 0.05 to 0.15,the ultimate axial force is 0.12 to 0.36 times to ealstic axial force.