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.     

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.     

A Study on the Test Method for Post-tensioned Prestressed Concrete Frame

A creative test method for post-tensioned prestressed frame is presented in this paper. In the test, the stationary supports at the column base are simulated and the forces at the column base can be tested while the two column bases are not connected with concrete beam. The prestressed secondary moment and the weight-produced moment are established by adjusting the support device at the column base. In this paper, the necessary conditions of the method and the basic process are recommended. It is proved theoretically that the prestressed concrete frame built by this method is equivalent to that used in practice.     

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.     

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.     

多点锚固体外无粘结CFRP预应力加固RC梁的抗弯性能

在梁侧或梁底用波形齿横向张拉CFRP片材并锚固的体外预应力加固混凝土结构技术,对3根完全相同的7 m跨T形截面梁进行加固：其中2根梁侧面加固;1根梁底部加固。试验表明：多点锚固体外无粘结CFRP预应力可以依据构件的弯矩来调整各段的加固量从而更有效的利用CFRP材料的高强性能;梁底与梁侧加固对提高构件的抗弯刚度差别不大;波形齿能彻底解决预应力CFRP片材的锚固问题。以该3根加固梁的试验结果为基础,提出了梁体极限状态下塑性绞区长度的体外无粘结预应力碳纤维加固受弯构件的抗弯承载力公式,以及考虑二次效应的有效惯性矩法的挠曲变形的计算公式,通过与试验值的对比分析可知,所提出的方法可供设计参考使用。     

Experimental Investigation of "Column with Weaker Beam" Frame and "Column with Equally Strong Beam" Frame

By the way of experiment and analysis of two "one story and one bay" reinforced concrete frames, namely a "beam with weaker column" frame and a "column with equally strong beam" frame, the features of internal force redistribution are investigated and an elementary comparison about bending moment redistribution of three kinds of frames namely the "column with weaker beam", "beam with weaker column" and "column with equally strong beam" is given. Through this comparison, the objective existence of such "three kinds of frame" is proven, the moment redistribution is different for each frame and for the moment modulation, the elastic moment diagram and the difference of the internal force redistribution in different frames should be considered together.     

A Simple Experimental Analysis Method for Reinforced Concrete Bar System Structures - Sectioned Dropping Rigidity Method

In order to solve the problem that the internal force of statically indeterminate prestressed and reinforced concrete bar system structures is difficut to determine when the structures come to the non-elastic state, a simple analysis method of experimental structures' internal force-sectioned dropping rigidity method is brought forward.In this method, according to the loading state of bars, the bars are divided into limited segments by the level of rigidity dropping, and the relative level of each segment is enacted; then the dropping modulus of each segment rigidity will be found by debugging time after time, and the checking point is the key distortion which was gained from the experiment; it is considered that the internal force which is calculated by elasticity analysis at the dropped rigidity can reflect the real internal force of the structures.It is basically proved that the method, which is brought forward in this paper, is effective by comparing its results with those from the experiment of a large size prestressed frame of two spans and single floor, of which the internal force redistribution is considered.     

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.     

Experimental Analysis on the Mechanical Properties of Concrete Composite Slabs with Precast Prestressed Rectangular Rib Panels

For the convenience of industrialized production and site operation,specification design of PPCRP (precast prestressed concrete ribbed panels) is discussed. In order to obtain ultimate bearing capacity,bending rigidity and crack resistance,four PPCRP with two types of spans are studied,and the results show that PPCRP can satisfy the requirements of bearing capacity in construction phase and can serve as stay-in place formwork. To verify the mechanical property,shear behavior on contact interface of composite member and moment redistribution factor of continuous composite member,two single-span composite members and one two-span continuous composite member are studied. It is indicated that computational method for bearing capacity of composite member can be the same as cast-in-situ concrete slab. Besides,section strain analysis for composite member in two-loading is conducted,which suggests that thickness of bottom board can be used as calculated height with the consideration of two-loading.     

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.     

Design and Test of an Exceedingly-long Prestressed Workshop Floor

Based on the project of a prestressed concrete beam-slab structure,this paper introduces the optimum design of a four-spanned exceedingly long prestressed floor. Different schemes,such as the scheme of the prestressed major beam,the scheme of the prestressed secondary beam with the same span and the scheme of the prestressed secondary beam with different spacing,are compared and analyzed in this paper.Meanwhile,various methods of the exceedingly treatment for long prestressed reinforcement are compared.Finally,based on two prestressed beams,the prestress loss,the prestressing value at the ends of the beam and the deflection in the midspan of the beam are detected during the tension and anchorage stage in order to verify the results of the theoretical analysis.     

Study on Equivalent Frame Model for Large-span Prestressed Concrete Residential Structure System

In this paper, a study is carried out on large-span prestressed concrete structure system in residence analyzed by specially - shape column equivalent frame model. Applying fiber model column-beam element and shell element, a large amount of comparative analyses about large-span prestressd concrete structure under horizontal and vertical load is carried out. The parameter of the equivalent frame is confirmed based on comparison with the result of the man-sized structural experiment. It is proved that the equivalent frame model has high efficiency and precision especially for nonlinear analysis.     

新型组合梁板连接中板的抗弯性能

在高层建筑结构设计中,由于上部荷载较大或梁的跨度较大,使得梁的截面高度较高,通常会影响建筑的有效层高和建筑的总体高度。为了减小各层梁板结构高度,有效增大各层净高,提出了一种钢箱梁嵌入现浇板的新型组合梁板连接方式。针对这种新型连接方式,对6个钢箱梁混凝土板组合连接区域进行了板承受支座负弯矩的单调加载试验,对比分析了采用钢箱梁嵌入混凝土板组合楼盖与传统栓钉连接组合楼盖中板抵抗支座负弯矩的性能差异;并利用ABAQUS对试件进行了有限元分析。试验与有限元分析结果表明：采用钢箱梁嵌入板连接组合方式,其混凝土板抵抗支座负弯矩的能力与传统连接方式板抵抗支座负弯矩能力没有明显差异。     

Composite Steel- concrete Frame Beam with Reinforced Negative Bending Regions

Considering the large negative bending moment at the end of frame beam and low tensile strength of concrete,a new composite steel-concrete frame beam(CSCFB),reinforced by a T shape steel beam at the negative bending regions,was brought forward.Through two full-scale of single-layer CSCFB frame models experiment,the load-displacement curves of CSCFB and strain distribution at cross section were obtained.Compared with the ordinary composite beam,the T shape reinforcing section can enhance the beam stiffness effectively,and make it distribute reasonably.The segment flexural rigidity method is presented and validated.     

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.     

Y形偏心支撑高强钢框架结构抗震性能

在Y形偏心支撑高强钢框架结构抗震性振动台试验的基础上,建立了试验试件的有限元模型,并验证了分析的正确性。设计了一个9层的Y形偏心支撑高强钢框架结构,以耗能梁段长度、耗能梁段腹板高厚比、高跨比为参数,对9层结构进行了非线性动力时程分析,研究了以上参数对结构抗震性能的影响。研究结果表明,改变耗能梁段长度、高跨比对结构层间侧移、耗能梁段性能、框架柱弯矩、耗能能力均有不同程度的影响,对框架柱轴力、基底剪力无显著影响;改变耗能梁段腹板高厚比对结构耗能能力有影响,对结构层间侧移、耗能梁段性能、框架柱受力、基底剪力无显著影响,并给出了相关设计建议。     

Mechanical Behavior and Techno economic Analysis of Twice prestressed Simply Supported Composite Beam

Excessive creep camber of prestressed concrete bridge would result in risk on the traffic safety in high speed railway. To control creep camber of presstressed concrete bridge, a new twice prestressed technology was proposed to presstressed concrete beam. Four twice prestressed simply supported box girders with different prestressed degrees were designed as an example. Its section stress, strength and crack resistance in different construction stages were analyzed. Compared the creep camber between conventional prestressed simply supported concrete beam and twice prestressed simply supported composite beam with the same prestressed steels, it was shown that twice prestressed composite beam has a smaller stress gradient. And the creep camber decreased approximately 40% to 60% with building height reduction, as well as some 10% energy saving and some amount of concrete.     

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.