Study On Secondary Internal Force And Redistribution Of Internal Force About Two-span Prestressed Concrete Frame

A historical analysis in theory is carried on studying redistribution of internal force in the bonded post-tensioned partially prestressed concrete framesin this paper. The main causes, which have effects on redistribution of internal force in the prestressed frame, including the relative height compressive zone of section, secondary moment and types of load applying are taken into account. The horizontal braces force which results from the tension of the prestressing steel, reduces the pre-compress stress is analyzed. The following conclusions are reached.(1) The relative height compressive zone of section or the axial force is bigger, the rotational capacity of the section is weaker.(2) The crack load increases with the increase of the amount of the prestressing steel or the tensioning stress. Influence of the amount of the prestressing steel and the tensioning stress to the crack load of the beam is greater than that to the crack of the column. The crack load of the frame applied horizontal load and vertical load is larger than that of the same frame applied vertical load only.(3) The relative height compressive zone of section greatly influences the redistribution of internal force of the prestressed frames. The total modulation of moment decreases according as the increase of relative height compressive zone of section.(4) The difference of the constraint conditions makes the second moment in prestressed frames less than that in the prestressed beams. Then the proportion of the modulation of moment taken by the second moment in the total modulation in prestressed frame is less than that in prestressed beam.(5) Horizontal load can increase the bearing ability of the section and the limiting load of the frame when value of is little. However, horizontal load can generates axial force and then deceases the ductility and bearing ability when is large. Then Limiting load is decreased.(6) Horizontal load can increase the coefficients of the modulation of moment when value of is little while decrease it when is large.