Experimental Study On Bending Behavior Of Prefabricated UHPC Formwork And NC Composite Beam

In actual engineering,as the main load-bearing member of the structure,the mechanical properties of the beam are not only excellent,but also have durability,but now the most widely used reinforced concrete beam,often because the external concrete over time cracks,resulting in internal steel rust,thereby affecting its service life.This is a major pain point in the actual engineering of bridges today,especially in coastal areas,chloride ions can corrode steel bars faster,reducing the service life of bridges.In this regard,this paper proposes a new form of stacked beam,prefabricated UHPC permanent formwork-NC stacked beam.In order to study the bending performance of precast UHPC permanent formwork reinforced concrete stacked beams,in order to prevent the peeling of the two materials,the test beams with different bonding methods were designed and tested,the influence of ribs and bolts on the bending performance of the new stacked beams was studied through the bending test,and the current specifications were verified,and further analysis was carried out through the finite element model,and the following conclusions were mainly obtained:(1)By co MParison,UHPC prefabricated permanent formwork can effectively inhibit the further development of cracks,so that the cracks change from the sparse,large and high crack characteristics of ordinary reinforced concrete beams to the crack characteristics of fine,small and small height,which significantly reduces the crack width and crack spacing.The reduction of the gap can effectively limit the entry of external substances into the components,so as to effectively avoid the corrosion of the steel bars,effectively increase the durability of the beam components,and greatly increase the service life of the bridge.(2)When ribbed and bolted methods are adopted,no slippage occurs between UHPC precast permanent formwork and ordinary concrete;When no ribs and bolts are used,there is slippage between the UHPC precast permanent formwork and ordinary concrete,and there is peeling damage.It shows that these two bonding methods improve the integrity of the stacked beam components,and whether there is separation between the precast formwork and ordinary concrete directly affects the protection degree of the shell to ordinary concrete.If separation occurs,the efforts to reduce the cracks will be abandoned,and the external substances will enter from the separation place,and the overall increase can effectively limit the entry of substances into the components,so as to effectively avoid the rust of the steel bars,can effectively increase the durability of the beam members,and greatly increase the service life of the bridge.(3)The introduction of the new UHPC prefabricated permanent template greatly improves the stiffness of the test beam and significantly reduces the ultimate deflection,indicating that the UHPC prefabricated permanent template reduces the vertical displacement of the beam to a certain extent.(4)With the introduction of ribs and bolts,the ductility of the ribbed and boltless stacked beams increased co MPared to the ribless and boltless stacked beams;Co MPared with ribbed and boltless stacked beams,the stiffness of ribbed bolt combinations is improved,and neither of them has peeling failure and ductility is reduced.While improving the bending performance of the beam,the influence of ductility should also be considered in the actual project,and the ductility can not be reduced simply to meet the requirements of bearing capacity and make it too rigid and lead to reduced ductility,so as to prevent brittle damage and accidents.