Study On Mechanical Properties Of Prestressed Ribbed Phosphogypsum Shell Hollow Composite Floor

At present,the application of phosphogypsum in building floors is relatively small,and phosphogypsum is mainly used in cast-in-situ ribbed hollow floors and beamless hollow floors.However,according to the research,it is found that phosphogypsum formwork with dense rib and beamless floor has problems in practical application,which is not suitable for prefabricated buildings,requires a large number of formwork and the construction process is complicated,and the phenomenon of formwork displacement and leakage of reinforcement will occur during construction,the difficulty increases,and the structure is complex.Based on the difficulties existing in the application of phosphogypsum formwork floor,a prestressed rib beam phosphogypsum formwork hollow composite floor system is proposed.The floor system is composed of prefabricated prestressed rib beams,phosphogypsum formwork and cast-in-place concrete.The hollow formwork adopts phosphogypsum to increase the consumption of phosphogypsum,which is suitable for prefabricated buildings and meets the needs of modern buildings.In order to make the floor widely used,the flexural bearing performance of the floor is studied.The main research contents and conclusions are as follows:(1)Summarize the research status of superimposed floors at home and abroad,and focus on the application of prefabricated rib beam hollow block superimposed floors abroad.(2)The model establishment method,procedure and material constitutive structure are described.Based on the test overview,the model of the reinforced concrete composite floor under uniform load is established.The stress and deformation characteristics of the floor were obtained,the load-deflection curve,yield and cracking loads of the superimposed floor were analyzed,and it was revealed that the simulation results of the superimposed floor were similar to the test results,and the correctness of the model establishment method was verified.The establishment of gypsum mould shell hollow superimposed floor model provides method and basis.(3)The model of the prestressed truss rib beam and the ordinary rib beam in the construction stage is established,and the existence of the truss steel bar can improve the bearing capacity of the rib beam.The influence of prefabrication thickness,truss web diameter,truss height and concrete strength on it mechanical performance was investigated.The research shows that with the increase of precast thickness and truss height,the deflection of the rib beam decreases continuously;the diameter of the truss web and the concrete strength have little effect on the force of the rib beam.The phosphogypsum prism and phosphogypsum mold shell models were established,and the influence of the width of the mold shell,the overlap length and the overlap thickness of the mold shell on the bearing capacity of the phosphogypsum mold shell was investigated.The overlap thickness can significantly affect the shell shear force,while the overlap length of the mold shell has little effect on the shell shear force.(4)Based on the research on rib beam and phosphogypsum formwork,the model of prestressed rib beam phosphogypsum formwork hollow composite floor and concrete hollow composite floor in use stage was established,and the load deflection curve and cracking load of the two floors were obtained.Similar to verify the safety of prestressed rib beam phosphogypsum mould shell hollow superimposed floor.The influence of rib beam thickness,truss upper and lower chord diameter,truss height,truss spacing and floor span on the bending bearing capacity of prestressed rib beam phosphogypsum formwork hollow composite floor was further explored.The research shows that increasing the thickness of the rib beam,increasing the height of the truss,and reducing the spacing and span of the rib beam can significantly improve the flexural bearing capacity of the prestressed rib beam phosphogypsum formwork hollow composite floor,while the upper and lower chord bars of the truss can significantly increase the resistance of the floor.The bending bearing capacity has little effect.(5)Based on the above research,establish three kinds of phosphogypsum mold shell hollow superimposed floor models under different span conditions,study the variation of floor deflection,and obtain the prestressed rib beam phosphogypsum mold shell hollow superimposed floor under each span condition optimal size design.The calculation formulas for the cracking load and ultimate bearing capacity of the superimposed floor are proposed.The results show that the theoretical calculation data of the cracking load and ultimate bearing capacity are in good agreement with the simulation results.It is of great significance to make suggestions on the construction of the prestressed rib beam phosphogypsum mould shell hollow superimposed floor,and to promote the application of the floor in practical engineering.