A Study on the Test Method of Post-tensioned Prestressed Concrete Continuous Beam

A test method of post-tensioned prestressed concrete continuous beam is presented in this paper.In the test,the prestressed secondary moment is established by adjusting middle support height.The prestressed concrete continuous beam built by the method is equivalent to the beam in practice.     

Study on the Application of Large-span Prestressed Concrete Frame in Added Floor and Rebuilding

Around the reconstruction design of the Popular Science Image Building of the Southwest Hospital, the advantage of prestressed concrete frame used in the rebuilding was approved. At the same time, the problem in the prestressed frame design was pointed out. In the end, the method to decrease the moment in the column had been put forward.     

Discussion on the Secondary Moment of Prestressed Frame

The secondary moment of prestressed concrete frame is different from that of continuous beam. In this paper,the principle and calculation method of equivalent load secondary moment and axial secondary moment are discussed,and the infection of secondary moment in moment modulation is analyzed,together with the suggestions of moment modulation for prestressed concrete frame with adopting the total control. The suggestions would be able to distinguish the advantageous and disadvantageous effect of secondary moment. Some helpful advises for moment modulation design are given in this paper.     

Curvature Force Method for Nonlinear Analysis of Prestressed Concrete Frame

In this paper, based on the structure characters and load applying means, a method called as curvature force method is put forward and proved in the nonlinear analysis of bonded prestressed concrete frame. Based on the nonlinear program, the simulation calculation was carried out on test results of two prestressed concrete frames by this method. The results from calculation are identical with the experiment ones. So it may be added to the methods for the nonlinear analysis of prestressed concrete frame.     

Experimental Study on a Prestressed Frame of Two Spans Under Unsymmetric Load

By the experimental study on a full-dimensioned prestressed frame of two spans, the relative factors are analyzed such as relative height of equivalent compression zone in critical section, secondary moment, ratio of beam rigidity to column and development of cracks in the top of columns etc., which influence the moment distribution of the post-tensioned prestressed concrete frame from the side of internal force redistribution. It is believed that that the factors of relative height of concrete equivalent compression zone and secondary moment influence the moment modulation in most degree, and ratio of column rigidity to beam also plays a part in the moment modulation to some extent. Second, the plastic joints of frame with excessive spans exit in the span which endure the whole load, at last the whole frame is destroyed because of the destruction of the loading frame, the influence to the non-loading span is little.     

Analysis Theory of Unbonded Prestressed Concrete Continuous Beams

In this paper, the energy method has been used to study the change of the secondary moment of unbonded prestressed concrete continuous beams and it has been contrasted with bonded prestressed beams. The question, whether the secondary moment changes or not while loading, was answered. It shows that the primary secondary moment does not change when increment method is adopted to study the beams, but the total secondary moment will change while the force in prestressed reinforcement changes.     

The Effect of Axial Compression on the Prestressed Concrete Frame under Vertical load

For prestressed frames, the axial compression ratio will affect not only the ductility of structures but also the structural internal force.Based on the computer-calculation for four groups of 24 prestressed frames combined with the references, in this paper, the effects of axial compression ratio on the prestressed frames are studied and discussed through three aspects: the second-order effect, the axial deformation of frame-columns and the comparison with ordinary concrete frames.The study results show that the effects of axial compression ratio on the prestressed frames and the ordinary concrete frames are basically consistent, but there are some self-born characteristics.As a whole, the effect of axial compression ratio on the prestressed frames is more notable than that on the ordinary concrete frames, but under common situation the effect is small.     

Test Analysis on Prestressed Frames with Three Kinds of Beam-column Section Strength

"Strong column with weak beam","strong beam with weak column" and"column & beam with equal strength"can be existed in one-storey prestressed concrete frames and the top storey of mult-storey prestressed concrete frames.Through the test of four prestressed concrete frames under vertical load,three kinds of prestressed concrete frames performances are studied,such as ultimate load,deflection,displacement ductility,redistribution of internal force.When the relative height of equivalent compression zone is smaller enough,the test proves that three kinds of prestressed concrete frames can realize full redistribution of internal force and have better displacement ductility,the width of cracks and deflections can satisfy the rules of code for design of concrete structures.     

Experimental Study on Moment Modulation of Prestressed Frames

Based on the experimental study of two prestressed frames in redistribution of Internal force, it can be concluded that the dominating influence factors on moment modulation are the relative height of equivalent compression zone, the secondary moment, the ratio of beam rigidity to column and development of cracks in the top of columns.The secondary moment is very important in modulation of frames. Especially, the secondary moment will governing the modulation when the relative height of equivalent compression zone is large enough.     

Several Matters to be Noticed During the Moment Modulation Design of Prestressed Concrete Frame

The moment modulation of prestressed concrete frame has some differences compared with that of continuous beam.Based on the analysis of ratio of column linear rigidity to beam one,form of load,second moment and plastic hinge in column,this paper is intended to get some helpful advise for moment modulation design.     

Suggestion for Moment Modulation of Prestressed Concrete Continuous Beams

Based on the information from China and overseas,a design suggestion for moment modulation of post-tensioned prestressed concrete continuous beams with bond has been put forth in this paper. The result calculated by the suggestion is consistent with the result of varying rigidity method.     

A Varying Rigidity Method in the Analysis ofStatically Indeterminate Prestressed Concrete Structures

A varying rigidity method is simple,convenient and accurate in analysing the statically indeterminate prestressed structures.The results from this method are verified by a series of large scale experiments.     

The Effect on the Column Moment Considering Compress of Prestressed Concrete Beam

Axial compress is produced by the tension of prestressing beam, which engenders the third moment of column. And the third moment is always ignored in design. The thesis analyses elementarily the third moment of column and finds that the third moment must be taken seriously in some condition, and it is not the same value as the manner of tensions is different . As a result, some helpful conclusion and suggestion are presented.     

Comparative Study on Plastic Hinges of Prestressed Concrete Frames Under Vertical or Horizontal Loads

In With one-storey, two-span prestressed frames, a comparative study is done between under vertical and horizontal loads. The studies include the pattern of the plastic hinges occurring and, the demanded and available rotational capability of the hinges in critical sections. The relative height of compression zone and prestressed degree are considered. The result indicates that there is much difference in the pattern of the plastic hinge occurring when each plastic hinge has enough rotational capability. The beams can finish a full redistribution of internal force under vertical loads, but not under horizontal loads. Moreover, as increasing of the relative height of compression zone, a stronger rotational capability of hinges will be demanded to finish a full redistribution under vertical loads when a weaker rotational capacity will be needed under horizontal loads.     

Uncertainty Analysis of Long-term Deformation for Prestressed Concrete Beam

Owing to the randomness of shrinkage and creep of concrete, random analysis method should be adopted to give a reasonable result with probabilistic guarantee. Stochastic variables for long-term analysis with GL2000 model about creep and shrinkage of concrete were presented. Combining Monte Carlo sampling with the response surface method, the stochastic analysis model was performed which is on time-variant deflection of prestressed concrete bridge. The long-term deflection of a prestressed concrete bridge was analyzed by this model. Sensitivity analysis and parametric study were carried out. And the uncertainty of creep model, elastic modulus of concrete, magnitude of sustained load, and prestress forces are the most important factors for long-term deflection. Furthermore, controlling accuracy of prestress forces and delaying the loading time are helpful to inhibit long-term deflection.     

Analysis and Optimization of Tension Sequence of Prestressed Reinforcing Steel Bars in Concrete Beam

Post-tensioned prestressed concrete beam in tensioning of prestressed reinforcement is based on the symmetry principle to determine the tensioning sequence.Simulation of the tensioning process of a 54m span post-tension concrect beam of a Prestressed Concrete Frame Structure in Fuxin was conducted with the finite element analysis program ADINA. With two different tensioning schemes,the influence of the tensioning sequence on deformation is calculated and then compared with the tensioning one by one in order the tensioning sequence is optimized.     

Construction Stage Analysis on Replacement of Closure Segment in Prestressed Concrete Cable-stayed Bridges

To deal with failure of wet joint between a closure segment and its neighboring segments of main girder in an existing prestressed concrete cable-stayed bridge, the technology on replacement of closure segment was presented. In order to analyze structural characteristics of this technology, its technical approaches and construction key points were introduced. Then a FEM model for a typical prestressed concrete cable-stayed bridge was established, and a construction stage analysis method was given in detail, including establishing a structural basement calculation model for replacement of closure segment and simulating its construction procedures. Based upon calculation results, variations of some structural state parameters with construction stages, such as deck deflection of main girder, longitudinal horizontal displacement at the top of pylons, cable forces, were analyzed. The results showed, this method could reflect actual change process of structural state and existing inspected results of cable-stayed bridge, and FEM results could well meet with construction monitoring results during replacement of closure segment. Thus variations of structural characteristics with construction stages could actually be revealed. This method could provide references for design and construction control of replacement of closure segment in existing prestressed concrete cable-stayed bridges.     

Mechanical Characteristics of Earthquake-Resistant Reinforced Concrete Frame Joints

On the basis of analysis and induction of experimental results on earthquake-resistant frame joint both at home and abroad, it is clearly pointed out that the mechanical characteristics of the joint in which shear failure may occur after yielding of longitudinal rebars at the beam end or at the column end are classified into three types, i. e ., diagonal tension, diagonal compression and a combination of diagonal tension and diagonal compression. A region of these three types of mechanical characteristics in the coordinates composed of relative shear force and relative ratio of transverse reinforcement is given, and the variation law and the corresponding reasons for the mechanical behaviors with the relative transverse reinforcement are analysed.