Experimental Research On Two Spans Prestressed Concret Frame Under Unsymmetric Load

Based on the experimental study of a prestressed frame of two spans under unsymmetric loading, the moment modulation of prestressed frames has been discussed. And the influence on the moment modulation of prestressed frames by ratio of column rigidity to beam,continuity of frames and the secondary moment etc. have been analysed. And some conceptional understanding and conclusion of moment modulation have been got.The moment modulation characteristics are mostly same of one and two spans frame.The height of compress area still influences the moment modulation by influencing the turning capacity.The secondary moment still has much influence on the moment modulation.In a "strong column and soft beam" frame, the plastic hinges always appear in the beam. The structure's destroy also starts from the beam plastic hinges.The load of a two more spans frame has little influence on no load span.A simple analysis method of experiments --Sectioned dropping rigidity method also has been found. The secondary moment of prestressed frames is changing during loading, and it often becomes less. So the modulation action of secondary moment becomes less too, but the modulation of load becomes more. So we should regulate the summation of the secondary moment and the load's when we regulate the amount of modulation.The ratio of column rigidity to beam influences the original elastic moment and the secondary moment. So it will influence the redistribution of internal force because the redistribution of moment by the rigidity dropping will be changed.