Analysis Redistribution Of Internal Force Of Prestressed Frames In Vertical Loads

Based on the experimental study of two presstressed frames, it analyses the question of redistribution of internal force and analyses influence of moment modulation of prestressed frames. Therefore, it draws some conclusion as follow:1) Post-tensioned prestressed frames can be practiced on moment modulation. But how to operate decides on practical situation in design.2) The secondary moment is an important factor on moment modulation. When ξ is small, influence of the secondary moment on moment modulation is small. Contrary, when ξis high, influence of the secondary moment is important. Sometimes it controls moment modulation.3) The relations between modulation of the secondary moment and modulation of load is very osculation. When ξbecomes greater, modulation of the secondary moment becomes greater. But modulation of the load moment reduces in more extent.4) As designing, modulation of the secondary moment must be considered. But when the secondary moment is very great, the whole secondary moment as modulation is unfit. There maybe have a fit reducing coefficient.5) The secondary moment postpones coming of plastic hinge on frames. In other words , it reduces requisition of rotation ability of section. Therefore, it maybe improve modulation ability of frame. However when ξis small, section has adequate rotation ability. The secondary moment has no influence on ultimate limit loads. When ξis high, rotation ability of section is shortage. The secondary moment improve ultimate limit loads of frames by improvement rotation ability of section.6) Horizontal braces force of horizon that results from tension. Therefore, it reduces pre-compress stress. Horizontal braces is stronger, it's influence is more important.7) In the prestesssed frames, direction of secondary moment of horizontal brace and secondary moment of equivalent load is sameness. Horizontal brace is stronger, secondary moment of horizontal brace is bigger.8) Crack of column has influence on moment modulation on prestressed frames. Crack of column equal to improve rotating ability of end of beam. Therefore ,it improves ability of moment modulation of end of beam.9) The secondary moment has important influence on crack load.