Experimental Research On Post-tensioning Prestressed Concrete Frame Under Vertical And Horizontal Loads

The technique of prestressed concrete is already to get in our civil engineering realm more and more extensive application. Because of its special function the prestressed concrete shows the greatly advantages to resolve the lacking of stiffness of concrete beam, to nicely control the development of the cracks and deflection of beam and acquire bigger safety store in long span construction. For the statically indeterminate structure of pestressed concrete, it is especially have the favor of the designers by its superiority. However now days the cognition about the behavior of such structure under loads is not enough for the realm of prestressed concrete all of the word.For example still the arguments exist about the cracking controlling, the behavior of secondary moment and the re-distribution of internal forces, especially for the moment, of the prestressed concrete continues beam or frame. To some degree those existing problems is due to the lacking of plenty of experiments with enough-size members that can reflect the practical structures effectively. To the prestressed concrete continues beam, considerable experiments have been finished and nice achievements have been acquired at Chongqing JianZhu University (renamed Chongqing University since the year 2000) in these years. But few of experiments have been finished about the prestressed concrete frame. And the finished experiments were mainly based on members with the shorten size and the vertical loads. For the comprehensive cognition to the prestressed concrete frame, four monolayer and monospan frames is built, two of which are loaded only vertically and the other two are loaded vertically and horizontally at the same time. In the experiments the fixed supports of the bottom of the columns are simulated creatively and the reaction of forces is tested. In this article the development of the cracks and the moment redistribution are discussed based on the two frames which are loaded vertically and horizontally at the same time. On the base of the research about the prestressed concrete structures at Chongqing JianZhu University, a convenient and practical way to control the cracks is introduced in the pages, which is called the method of nominal tension stress that control the width of cracks by the nominal tension stress γftk under the working loads and the limited loads. The discussion is focused on the moment redistribution of the frames, the effects of the secondary moment and horizontal loads under the loads vertical and horizontal at the same time. In conclusion, a formulae about the moment distribution is introduced on the consideration of several factors, which is suggestive for the designing of practical prestressed concrete structures.