| Construction is an industry with huge energy consumption and resources consumption.The current construction mode of production in our country is mainly based on reinforced concrete structures,which has a low efficiency,a low degree of industrialization,huge building materials wastage,unstable construction quality,large building garbage and high whole life cycle of building energy consumption.This does not match the national policy of energy-saving,environmental protection.Prefabricated structures,as a kind of conforming to the demands of industrial production,have superior economic,environmental and social benefits and good structural performance.The kind of new structures has been widely applied in Europe,the United States,Japan and other developed countries.Due to the fact that there is a relatively low level of industrialization in our country,prefabrication assembling technology is in its infancy.So it is necessary to reform prefabricated concrete structure system and deepen theoretical and experimental research so as to impel the application of prefabricated structures in our country.To conform to the development trend of building industrialization,a new type of Precast Prestressed Assembled Structural System(the System of PPAS)is proposed by Huahui Architectural Technology Co.,Ltd.and Southeast University.By using the precast prestressed beams with the end connecting with channel steel,short steel tube columns and ribbed corrugated boards and related components,PPAS system has obvious technical advantages: less pillars,low beam height,good use performance,convenient construction,low cost,environmental protection,etc.In this paper,the Precast Prestressed Assembled Structural System(PPAS system)is theoretically studied and analyzed.The composition and construction method of the PPAS system are studied.The stress release of the prefabricated prestressed beam steel strand in the PPAS system and the anchorage of the steel stranded wire in the node area are studied by the node test and the finite element analysis.On this basis,the more reasonable node forms and related technologies of the PPAS system are proposed to improve and improve the seismic performance of the PPAS framework.The seismic performance of the improved PPAS frame is studied by frame test and finite element analysis.The main work and achievements of this paper are as follows:1.The system construction of the PPAS system.On the basis of summarizing the research and application results of node connection technology of precast frame structure and prefabricated composite beam,a new type of Precast Prestressed Assembled Structural System(the System of PPAS)is proposed.The main technical features of the PPAS system are the unsupported construction and the use of new preprestressing beams.The prefabricated prestressed beam of PPAS system uses high strength steel stranded wire as the lower longitudinal stress reinforcement,and makes full use of material properties to build a large span assembly frame.The prefabricated prestressed beam ends part of the steel strand coat PVC sleeve releases stress to avoid the cracks in the concrete pre pressure,and the precast prestressed beam ends with the connecting channel steel with the end of the prestressed beam and the end of the precast prestressed beam.The short steel pipe at the top of the column is quickly assembled by high-strength bolts to form a temporary loading system to bear the construction load.2.Three groups of full-scale precast prestressed beam assembled monolithic frame system(PPAS)node test specimens and a cast-in-situ specimen for contrast has been designed,whose low reversed cyclic loading tests have been carried out.Three groups of specimens include three PC1 groups of specimens with different prestress release status,two PC2 groups of specimens with different anchorage state and two PC3 group considering the influences of composite plate specimens.Low reversed cyclic loading tests for three groups of full-scale precast prestressed beam assembled monolithic frame system(PPAS)node test specimens and a cast-in-situ specimen for contrast have been carried out.Experimental results show that all specimens PC1 groups have good energy dissipation capacity and all specimens have full hysteretic curves.Positive loading skeleton curves are basically the same and negative loading skeleton curves differ slightly.With the increase of steel strand prestressing release quantity,the skeleton curves of the ultimate load decrease and ductility and energy dissipation capacity performance decline to some extent;two specimens in PC2 groups with different number of strands in the node area did not use the additional anchorage measures such as anchor plate and only relied on the bonds between steel wire and concrete.In the process of the test,great slippage of the steel strand happened,steel strand surrounding concrete with steel wire were pulled out and appeared local damage phenomenon.The hysteresis curve of the two parts of PC2 groups was obviously squeezed,and its skeleton curve was obviously elastic,and the ductility and energy dissipation of the two specimens were extremely poor.Two specimens in PC3 group mainly consider the effect of composite slabs node performance.Due to the fact that the ordinary reinforced steels in composite beams and composite plate yield strength is too high,in the process of test PC3 group upper two specimen were damaged when ordinary reinforced steels were not yield.The hysteresis curve of the specimens pinch phenomenon is obvious.Its skeleton curve showed unconspicuous yield,poor ductility and energy dissipation performance.3.According to the hysteretic curve and skeleton curve of the low cycle repeated load test of the PPAS system node PC1 of the PPAS system with good seismic performance,the skeleton curve and hysteresis curve of the node recovery force model of the PPAS system are established.The paper introduced the development of the nonlinear finite element analysis software OpenSEES.It created the section fiber model,established PPAS system node finite element model of nonlinear finite element,analyzed under low reversed cyclic loading,and the calculated hysteretic curves,skeleton curves and experimental hysteresis curves,skeleton curves were compared.On this basis of this,the parametric analysis has been carried out by considering the different strength grades of concrete axial compression ratio on the seismic performance PPAS system nodes.4.On the basis of low reversed cyclic loading tests of PPAS system,the two problems that precast prestressed composite beams too little and the number of cracks and crack width is too large have been solved by increasing ordinary energy-dissipation steels at the bottom of the precast prestressed composite beam.The low reversed cyclic loading tests were carried out in the two common PPAS systems.The experimental results show that the PCF1 framework and PCF2 framework have better seismic energy dissipation capacity with full hysteresis curves,better ductility performance and better energy dissipation capacity.The maximum interlayer displacement angles of PCF1 specimens and PCF2 are 4.1% and 5.01% respectively,which meet the requirements of the seismic design code for the elastic and plastic displacement angle limit of the frame structure.The displacement ductility coefficients of PCF1 and PCF2 specimens are 4.08 and 4.75,respectively,to meet the aseismic requirements of the reinforced concrete frame.5.The prestress loss of preprestressing beams in the PPAS system is calculated,and the results are compared with the finite element simulation results and the measured results.The calculation method of the cracking moment of prefabricated prestressed composite beams is studiedThe formula of ultimate bearing capacity of positive bending moment and negative bending moment of preprestressing beam is derived by using geometric conditions and equilibrium conditions.And compared with the experimental results,the ultimate bearing capacity calculation formula can calculate the ultimate bending moment of preprestressing beams in PPAS system relatively accurately. |
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