Study On Mechanical Properties And Design Method Of RC Beams Under The Coupling Effect Of Coal Mine Natural Environment And Static Load

Under the coupling effect of coal mine natural environment and static load,compared with the concrete structure of ordinary atmospheric environment,the concrete structure of its concrete structure will have the durability problems such as deterioration of structuralmember damage and reduction of bearing capacity.On the basis of existing achievements,this paper using artificial climate chamber simulated conditions of coal mine natural environment,the method of joining the load coupling factors,under the coal mine natural environment carry out the simulation of concrete material performance and the rule of the reinforcement mechanics performance,coal mine natural environment and static load coupling under the action of both RC structural behavior and design method of the research.Main conclusions and innovations are as follows:1.The degradation law of physical and mechanical properties of concrete under the coupling effect of coal mine natural environment and static load is analyzed from macroscopic and microscopic aspects:The compressive strength of damaged deteriorated concrete decreases with the increase of corrosion time and the carbonization depth increases linearly.The compressive strength of degraded concrete decreased continuously after increasing by 2.6%in the early stage,and the carbonization depth increased gradually.With the increase of corrosion time,element of degradation,and degradation products continues to grow in the concrete;2.Under the coupling effect of coal mine natural environment and static load,the corrosion rate of corroded steel bar reaches up to 6%.With the increase of corrosion time,the corrosion rate of steel bar increases gradually,and the relative value of nominal yield strength and nominal ultimate strength of steel bar decreases gradually.Establish the relative magnitude of the nominal yield strength steel and ultimate strength steel and corrosion rate.In the same test beam,the corrosion rate of stirrup is higher than that of main tendon,and the corrosion rate of stirrup in the shear pressure zone is higher than that of pure bending section;3.Under the coupling effect of coal mine natural environment and static load,the deteriorated and damaged deteriorated beams begin to appear the corrosion cracking.The main form of destruction is bending failure.The cracking load and ultimate load of the test beam slowly decreased,while the ductility first increased and then decreased gradually;4.Under the coupling effect of coal mine natural environment and static load,the bearing capacity and deformation capacity of the deteriorated and damaged deteriorated beams gradually decreased with the test time.When the strength of degraded beam is reduced by 16.8%compared with that of undegraded beam,the corrosion rate of reinforcement reaches 4.57%,the bearing capacity of RC beam is decreased by 17.23%,and the ductility coefficient is decreased by 14.9%.When the concrete strength of damaged deteriorated beams deteriorates by 17.27%,the corrosion rate of reinforcement reaches 5.08%,the bearing capacity of RC beams decreases by 22.31%and the ductility coefficient by 46%.And in the existing beam cross section flexural bearing capacity calculation model,based on the revised considering steel bar corrosion,concrete mechanics performance degradation,cross section geometry damage and static load factor of coal under under the coupling effect of coal mine natural environment and static load coupling damage degradation RC beam method to calculate the ultimate bearing capacity theory:Mc,u=fy,cAs(he-fy,cAs/2α1fcbe)deterioration of beams:fy,c=fy0(-0.021p +0.9905)ρ≤6%、fc’=0.1029T2+0.0954T + 15.9175 damage deterioration of beams:fy,c = fy0(-0.024ρ+ 0.9772)ρ≤6%、fc’=0.4066T+15.6636。...