Study On Static Performance Of Concrete Simply Supported Beams With Rebars Of Large Diameter

At present,the prefabricated components have the problems of complex reinforcement,difficult installation quality and imperfect traditional cast-in-place method in assembly building.Configuration of 500MPa large diameter and large spacing steel bars can reduce the number of mechanical connections of steel bars,reduce the number of longitudinal reinforcement rows,and effectively reduce construction costs and construction difficulties.For assembly concrete beam members,direct installation at the end of the beam can further simplify the connection between support and joint.To realize the design concept of simple fabrication,convenient installation and appropriate cost,improve the production efficiency,building quality and environmental quality of prefabricated components,and promote scientific and technological progress in the field of green building and building industrialization.In this paper,the mechanical properties of prefabricated concrete simple-supported beams with large diameter and high strength steel bars are studied,which can provide relevant reference for engineering design and construction.In this paper,central pull-out test is used to study the bond strength between HRB500 grade steel bars that diameter of 25 mm and 32 mm with high strength concrete,so as to obtain the bond strength relationship between large diameter high strength steel bars and high strength concrete.The results show that with the increase of the diameter of steel bar,the pull-out force between steel bar and concrete increases gradually,while the bond stress between them decreases continuously.In this paper,six full-scale precast reinforced concrete simple-supported beams with 350 mm and 700 mm cross-sectional dimensions and 7600 mm span are designed and fabricated.They are divided into two groups:(?)32 and(?)40 respectively.Each group of specimens is selected to tie the additional bar 3(?)12 at the joints of the mid-span waist-bar joints.The failure modes,the overall performance of the section,the flexural capacity,defomation capacity and cracks of the two groups of prefabricated beams under monotonic static loading are studied.The static test of simply supported beams is carried out,and the occurrence and development of cracks,flexural deformation,failure characteristics and ultimate bearing capacity are observed and recorded in detail.According to the strain,cracking load and bending moment,ultimate load and bending moment of the specimens measured during the test,it can be seen that the mechanical performance of the simply supported berms with large diameter precast concrete is good,and the bending moment-deflection curve has been obtained.It has obvious turning point,good ductile failure characteristics and good working condition.The static performance analysis of large diameter precast concrete simply supported beams is carried out,and the flexural capacity of large diameter precast concrete simply supported beams is judged by comparing the measured values of failure moment of the test beams with the calculated values of the standard formulas,to verify whether the deflection and maximum crack width of simply supported beam meet the requirements of the code under normal service condition,and to propose the maximum crack spacing expansion factor based on the test results,to compare the failure deformation curve of the test beam,the relationship between the ductility of the simply supported beam and the diameter of the steel bar is obtained.ABAQUS finite element methody is used to simulate the non-linear analysis of large diameter precast concrete simply supported beams.The stress process of the test is simulated.The relationship between the finite element simulation results and the ultimate bending moment and load-deflection curve of the test results is compared and analyzed.