Experimental Investigation On Shear Lag Effect Of Carbon Fiber Composite Continuous Box Beam And Cantilever Box Beam

Carbon fiber composite box beam have good mechanical properties, lightweight, corrosion resistance and fatigue resistance etc, and so have a good development and application prospect in civil engineering structure. At present, for carbon fiber composite box beam, research work is still relatively short. In this paper, in order to get the shear lag effect of the carbon fiber composite material continuous box girder and cantilever box girder when consider different layer angle and different width span ratio, the ANSYS finite element software and experiment are used together to make analysis.In this paper, mainly completed works are listed following:(1)ntroduced the FRP materials, box girder and the shear lag effect.Introduced carbon fiber composite material box girder’s research situation at home and abroad, made clear the research content and method of this paper.(2)According to the national standard, made five single layer carbon fiber slabs, through the tensile test get the elastic modulus and Poisson’s ratio of single carbon fiber board. Make [0°/0°/0°/0°/0°,[0°/45°/0°/-45°/0°,[0°/90°/0°/90°/0°three kinds layer angle of carbon fiber laminated plates, each layer angle do five boards, then respectively do the tensile test to the15carbon fiber laminated plates, measure elastic modulus and Poisson’s ratio, which can provide reliable mechanical parameters for carbon fiber box girders’ research.(3)In the continuous beam’s study, the first thing to do is to calculate the stress distribution curve of the single span across the floor and in the roof of bearings by ANSYS finite element software, and calculate the changing rule of the shear lag effect. To the negative shear lag effect produced from the middle bearing and in the different layer Angle, summarizes that in the middle of the bearing roof can produce negative shear lag effect at the corresponding width span ratio when under different layer angles. And then analyze the middle span deflection, getting the changing rule of middle span deflection with different angle layer and different width span ratio. Combined with angle layer, get the way of reducing shear lag effect and improving stiffness. Finally make carbon fiber composite materials box girder models with different layer and different width ratio, for which do static load test, get strain and deflection, through the comparison, get a conclusion that the test value and the calculated value of ANSYS finite element can meet each other. (4)For cantilever beam,first calculated the stress distribution curve of its two cross section by ANSYS finite element software,calculating the shear lag coefficient,get the change rule of shear lag and minus shear lag with width span ratio and layer angle. Through the analysis of the y=0and y=b two longitudinal section’s shear lag effect, get the change rule of shear lag and minus shear lag’s boundary along with different cross wide than and different layer angle. Introducing a coefficient N which is the ratio of the beam length of producing negative shear lag effect and the cantilever beam’s total length,through the ANSYS finite element analysis width span ratio and layer Angle’s influence to the ratio N. And then analysis the cantilever beam’s free deflection, get the free deflection’s variation law with the Angle layer and the width span ratio. Finally, by doing the nine cantilever beam model’s static load test, verify the rationality of ANSYS finite element calculation and test.(5)Using the ANSYS finite element software to simulate the cantilever beam with eccentric loads,through the comparison and analysis of the calculation results of ANSYS finite element and the test result,get the variation law of the cantilever beam’s across and fixed section’s stress distribution with the layer angle and width span ratio, and the reverse Angle of free changes.(6)Analyzing some of the factors which easy to cause error in the test process,combined with carbon fiber composite box-beams’making process to overcome some of the problems, Puts forward some suggestions for other composite box-beams’test to be smoothly fininshed.