Study On Flexural Behavior Of Post-cast Self-compacting Composite Beams

Prefabricated composite beams in prefabricated buildings are an important part of prefabricated buildings.The key of their application is to realize the "equivalent cast-in-place" of the composite beams in prefabricated buildings.The safety design and convenient construction of the composite beams in prefabricated buildings under static load are the basis of the application of architectural engineering.For the general prefabricated composite beams,the research on their mechanical performance and theoretical calculation is quite sufficient,and there are also relevant provisions in the code.But for the assembled composite beams with splinted joints,the research at home and abroad is not enough,lack of relevant experimental research.According to the component arrangement scheme of the prefabricated concrete structure,the prefabricated composite beams can be spliced in the mid-span of the prefabricated beam body,or at the end of the prefabricated beams and the cast-in-place beam-column joints or the cast-in-place dark column joints.No matter what kind of connection is adopted,the spliced joints will be produced between the prefabricated components.Therefore,it is of great significance to study the mechanical properties of assembled composite beams with splinted joints.In this paper,the flexural behavior of post-cast self-compacting concrete composite beams is investigated,including failure mechanism,bearing capacity,deflection,crack distribution,etc.,and is compared with that of whole-cast reinforced concrete beams.Five post-cast self-compacting concrete splice composite beams were designed as test beams.The precast ends were cast with C30 ordinary concrete,and the post-cast part was cast with C30 self-compacting concrete.At the same time,an integral cast-in-place beam was designed as a control beam,which was all cast with C30 ordinary concrete.Through the bending tests of six beams,the mid-span deflection and crack development laws and failure characteristics of post-cast self-compacting composite beams are obtained.Using the existing hydraulic concrete structure design code(SL/T 191-2008)after the relevant calculation formula for watering the self-compacting concrete splicing theoretical calculation of the cracking moment of the composite beams,according to the specification for design of concrete structures(GB50010-2010)after the relevant calculation formula for watering the splicing self-compacting concrete composite beam theory yield moment,ultimate bending moment is calculated,and using the large general finite element software ANSYS specimen of beam by Dutch destroy the whole process of numerical simulation has been done.The flexural mechanical properties of post-cast self-compacting concrete composite beams in prefabricated buildings were systematically studied by means of experimental research,theoretical analysis and numerical simulation.The main research contents of this paper are as follows:(1)Through reading a lot of relevant references,determine the research background and significance of this topic,expounds the advantages of prefabricated buildings and self-compacting concrete,as well as the development and research status of prefabricated buildings at home and abroad,and puts forward the technical route of this paper.(2)Six specimen beams were designed and made.After 28 days of laboratory maintenance,the bending performance test was conducted to observe the failure pattern and crack distribution pattern of the beam body under bending.The mid-span displacement and the strain of the lower tensile reinforcement under the action of the three-equal point stress of the simply supported beam were measured,and the test data were recorded and analyzed.(3)The load characteristic value,short-term stiffness and displacement ductility coefficient of the specimen beam were calculated by using the code,and compared with the test results to verify the validity of the test data and the credibility of the test results.(4)Finite element simulation software ANSYS was used to carry out numerical simulation on the whole process of the actual stress failure of the specimen beam,to analyze and calculate the mid-span displacement and the strain of the lower tensile reinforcement under the same loading conditions as the test,and to verify the rationality of the model and the reliability of the simulation results by comparing with the test values.