| With the rapid development of subway in China,more and more subway segments crack and spall,which affect the structural bearing capacity and durability.As a solution,steel fiber concrete has received great attention.Steel fiber is introduced into ordinary concrete,which can provide a certain residual tensile strength after the structure cracking,so as to improve the toughness and durability of the structure effectively.In addition,this can reduce the amount of rebars,and can even use steel fiber reinforced concrete structure directly in some structures.And the tensile stress of the structure can be assumed by steel fiber.However,there are some deficiencies in the development of steel fiber reinforced concrete cracks.Therefore,the research and analysis on the crack development of steel fiber reinforced concrete with no steel bar is urgently needed.Taking the shield-driven tunnel works of the car depot in line 9 of Shenyang Metro as the research background,this paper has carried on the basis of mechanical tests and component tests,records the crack width,height and spacing under various load combination,and emphasizes on the research of the crack development of steel fiber reinforced concrete with load changing by the methods of Theoretical derivation,mechanism analysis and numerical simulation.For this purpose,the following work was carried out:The axial compressive and residual tensile strength tests of six different concrete strength,different steel fiber types and different steel fiber contents were carried out.Based on the tests of the incisional beams used in residual tensile strength tests,the results show that,when the incision displacement reaches 1.5mm ~2.5mm,the beams with the C50 concrete and 4D steel fiber have greater bearing capacity.With the displacement of the incision increasing,the tensile strength of steel fiber is the main factor affecting the bending performance of the beam,so the concrete capacity of 5D steel fiber is larger.By the tests of the press-bend beams and inclining beams of the steel fiber reinforced concrete with 2400mm×400mm×300mm,this paper compares and analyzes the data of same eccentricity but different tensile strength.The results show that the tensile strength of steel fiber reinforced concrete is the main factor.If the compressive strength of steel fiber concrete is certain,with the higher tensile strength,the structure has the higher corresponding bearing capacity,so it’s easier to meet the design requirements.Based on using press-bend beams with no rebar and only steel fiber reinforced concrete tests to simulate crack development of the segment,the result include the cracks width,height and spacing under various load combination.It summarizes the mechanism and law of crack development in steel fiber reinforced concrete,and with enhancement mechanism combined of fiber concrete,studies the interrelation of the crack width and height development and the load change,by the way of the theoretical analysis,data fitting and formula derivation.The finite element analysis software ABAQUS is used to analyze the test process of steel fiber reinforced concrete by numerical simulation.Calculation model is chose as the plastic damage model,with the model parameters using steel fiber concrete constitutive relation and the tensile damage factors obtained from the amending Loland damage model.Through numerical simulation,the result reflects the multipoint cracking characteristics of steel fiber reinforced concrete with no rebar better.Comparing the results with the field test results,numerical simulation result has the similar crack development trend.And load internal force calculation is reasonable.Using this method to simulate the load capacity of steel fiber reinforced concrete segment,the result proves that it is useful in the subway segment. |
