Study On Mechanical Behavior Of Composite T-beam With Full Prefabricated Plate Connected By Dark Beam

Prefabricated concrete structure has the advantages of high quality,short construction period,energy saving and environmental protection,and has been widely used in construction.Floor is the main load-bearing component of the building.At present,the research on precast floor is mainly focused on composite slab,while the research on fully precast floor is less.Therefore,the research group proposed a new type of full precast slab with concealed beam.At present,the research group has completed the research on the bending mechanical properties of the middle plate of the precast T-shaped composite beam formed by the full precast slab slab connection and the rectangular beam full precast slab connection.On the basis of the above research,this thesis will carry out the research on the bending and shear mechanical properties of the above precast T-shaped composite beam,so as to provide a reference for the design of this kind of concealed beam precast slab.This study will help to promote the application of precast beam and slab in prefabricated concrete structure,and has a good engineering development prospect.In this thesis,the previous tests are briefly introduced,and then the finite element software is used to establish the simulation T-beam specimens which are exactly the same as the previous tests.The accuracy of ABAQUS finite element simulation method is verified through the comparative analysis of the failure mode,bending capacity and other aspects of the test T-beam and the simulation T-beam.The results show that the failure modes are the same;the results of cracking,yield and ultimate load are basically consistent with the test values;the load displacement curves are basically consistent,and the variation rules are the same;the short-term stiffness and displacement ductility are relatively close.The reliability of the finite element simulation is illustrated.By using the finite element software,the precast T-shaped composite beam specimens with the same size,strength and configuration as the simulated T-beam are established.Through the comparative analysis of their failure modes and load displacement curves,the feasibility of bending mechanical properties of precast T-shaped composite beam is explored.The results show that: the bearing capacity and ductility of the specimen are basically the same as that of the cast-in-place structure;the integrity of the section is good,meeting the requirements of the plane section assumption;the short-term stiffness before cracking is less than that of the cast-in-place structure;the slip between the precast beam and the post cast strip is small,so it is considered that there is no relative slip between them.The overall performance is consistent with the cast-in-place structure,which has engineering feasibility.The influence of different factors on the bending mechanical properties of precast T-shaped composite beams is analyzed by finite element simulation method.The results show that: the lap length of precast slab and the spacing of shear stirrups are the main factors affecting the precast T-beam specimens;the friction coefficient between the new and old concrete and the strength of post cast concrete have a significant impact on the displacement ductility of the specimens;the diameter of longitudinal reinforcement at the joint and the area of shear stirrups have a certain impact on the bearing capacity of the specimens;the area of shear stirrups has a certain impact on the short-term stiffness of the specimens There is no influence on the bending performance of the longitudinal reinforcement at the joint.At last,the parameters of precast T-shaped composite beam are suggested.Combined with the Chinese code,the calculation formula of bending capacity of precast T-shaped composite beam,the configuration method of shear stirrups on the composite surface,and the reduction factor of short-term stiffness are given.