Research On Mechanical Behavior Of GFRP Pultruded Profiles Built-up I-shape Beams

GFRP pultruded profiles have many advantages,such as light weight,high strength,good corrosion resistance,good designability and excellent elastic properties.Due to the production technology and capacity of pultruded profiles,the existing GFRP pultruded Ishape beams can not meet the stiffness requirements of relevant codes when applied to bridge structures.This paper is supported by the national key research and Development Program(2017 YFC0703005).In order to solve this problem,two T-shape pultruded beams are combined vertically to form an I-shape beam,the mechanical behavior of GFRP pultruded profiles built-up I-shape beams is studied.The main research contents and conclusions are as follows:The mechanical behavior tests of 5 GFRP pultruded profiles I-shape beams were carried out,the failure mode,load-displacement curve,strain distribution in the middle section of beam,strain distribution in the bending-shear section and strain distribution in flange are analyzed.The results show that when the shear span ratio is small,the shear failure and the local compression failure of GFRP pultruded profiles I-shape beams are longitudinal cracks in web and flange is crushed near the loading point,respectively.When the shear span ratio is large,the bending failure of beams occur,and the transverse cracks appear on flange near the loading point and penetrates down to web The shear strain distribution of beams conforms to the material mechanics theory basically.The shear strain at central axis of web increases and decreases gradually at both ends.The contribution of flange to shear resistance can be neglected in the calculation of this kind of beam.The mechanical behavior tests of 6 GFRP pultruded profiles built-up I-shape beams were carried out,the failure modes of specimens,load-displacement curves,strain distribution of the middle section of beam the shear strain distribution of bending section and the flange strain distribution are analyzed.The results show that when the shear span ratio is small,the shear failure and the local compression failure of beam with small crosssection occur,respectively,Longitudinal cracks in web and flange are crushed near the loading point,and torsion failure of beam with large cross-section occur After lateral bracing treatment,the beam with larger shear-span ratio appears transverse crack at flange near the loading point and penetrates to web,and the flat section assumption can be used to calculate GFRP pultruded profiles I-shape beams.The shear strain distribution of the web of beam basically conforms to the material mechanics theory.The contribution of flange to shear resistance can be neglected in the calculation of this kind of beam,which is more conservative.The effects of shear-span ratio,bolt spacing and bond of web on the mechanical behavior of GFRP pultruded profiles I-shape beams were analyzed by finite element method.The results show that when shear span ratio is small,shear failure mode usually occur,and longitudinal cracks appear at the junction of flange and web or in the middle of web,I-shape beams and built-up I-shape beams with smaller section size are prone to shear failure,and finally longitudinal cracks appear at the junction of web and flange,web as well as near the web hole,built-up I-shape beams with larger cross-section are more likely to be bent,and the transverse crack appears at flange near the loading point and the support even penetrates through the web.The influence of shear span ratio on the mechanical behavior of I-shape beams is greater than built-up I-shape beams,and the influence of bolt spacing on the overall performance of GFRP pultruded profiles built-up I-shape beams is greater,this is directly related to beam’s stiffness and bearing capacity,but the relationship between the bolt spacing and the beam’s bearing capacity and stiffness is not linear,and each kind of beam has its own optimal bolt spacing;For GFRP pultruded profiles built-up I-shape beams,when shear span ratio is small,the web interface bonding can greatly increase bearing capacity and stiffness of beams,and when shear span ratio is large,the interface cementation can only increase the stiffness of beam for the main stress state of beam is bending,and has little effect on bearing capacity.