Experimental Research On Concrete I-shaped Beam Reinforced By HWFC Composite Layer

Relying on the project of science and technology of construction of the Ministry of Transport(2013 318 J15 390)"the application technique research of SWFC composite structure in continuous rigid frame bridge in Tibet)",aiming at the cracking disease and steel-bar corrosion problem caused by leakage for existing concrete continuous beam bridges(including continuous rigid frame bridge)to withstand negative moment,tutor Professor Zhou Zhixiang proposed laying high content hybrid steel fiber reinforced concrete composite layer with fine-pitch ribbed steel-bar web("HWFC composite layer" for short)method to reinforce the top slab of beam.Combined with the current research at home and abroad,the paper takes concrete I-type beam for the study,experimental studies and theoretical analysis of concrete I-shaped beam and which reinforced by HWFC composite layer under the action of the negative bending moment have been carried out,main researches and work are carried out as follows:?The load carrying capacity test of 3 concrete I beams under negative bending moment is carried out,the mechanical behavior of the concrete I beam under the negative moment is studied of the whole loading process from the beginning to the damage.The test results showed that the first crack of the concrete I beam under the negative moment appeared at roof flange,with the load increasing,the crack gradually extending to the web;the failure deformation of concrete I beam has the typical characters of plastic failure:firstly the steel-bar or steel-plate in the tension zone yielded,then the flexural deformation significantly increased,the beam rode up continuously until the concrete of compression zone crushed in the end.?Putting the high content hybrid steel fiber reinforced concrete composite layer with fine-pitch ribbed steel-bar web(HWFC composite layer)into reinforcing the tension slab of the 3 renovated concrete I beams;the damage test of 3 HWFC reinforced beams is taken under the load in the similarly cantilever beam mode on the left and right side.The test results showed the HWFC composite layer reinforcing method can effectively improve the anti-cracking ability of the top slab of the component,the cracking moment of the reinforced beam is improved by 45%compared with the cracking moment of the original nondestructive beam;meanwhile the HWFC reinforcement layer can effectively improve the crack resistance of the beam,the crack width of the reinforced beam is reduced by 30%-50%compared with the crack width of the original nondestructive beam;in addition,the ultimate bending capacity of the test beam after the addition of HWFC composite layer is improved to 25%.?Based on the deformation coordination and static equilibrium,the cracking moment calculation mode of the reinforced beam is established,the relevant calculation coefficient is obtained combined with the experimental data;basing on the crack width calculation formula in current concrete structure design codes,the formula for calculating the maximum crack width of concrete I beam after reinforced with HWFC composite layer is established by replacing the steel-bar tensile strain with the macro tensile strain.? In a Tibet reinforced concrete continuous rigid frame bridge with large longitudinal slope and small radius in plane,the reinforcement method of replacing the concrete deck pavement with HWFC composite layer in the negative moment section of the main girder is proposed,aiming at improving the crack resistance of the top slab of the main girder.The crack width of deck is checked after the 10cm thick HWFC composite layer is included by the formula proposed in the paper,the checking result showed the deck of the bridge can meet the anti-cracking requirements under the design load.