| As the most commonly used shear connector in steel-concrete composite bridges,stud connectors have been widely used in bridge engineering.The stud connectors are arranged between highway steel main beams and concrete bridge slabs,railway steel bridge slabs and concrete road anvils often only consider the fixed effect,and do not consider the combined force of the two materials.Due to the large stiffness of the stud connector itself,the local shear force on the stud connector at the initial stage of loading is relatively large,which may easily cause the concrete to be crushed or cracked.Therefore,it is particularly important to research and develop new stud connectors with higher durability and better deformation performance.In this dissertation,steel fiber reinforced concrete(SFRC)is used instead of ordinary concrete and rubber sleeve is added at the root of the stud to form SFRC stud rubber-sleeve shear connector,and its shear performance is studied.The main research work includes the following aspects:(1)Through the volume fraction of steel fiber 0%,0.4%,0.8%,1.2%,1.6%,concrete strength grade CF30,CF40,CF50,CF60,the diameter of the stubs is13 mm,16mm,19 mm,22mm and 25 mm.The height of the rubber-sleeve accounts for 25%,50%,75% and 100% of the height of the stud.The thickness of the rubber-sleeve is 2.5mm,5mm and 7.5mm.The arrangement of the studs(rows ×ranks)is 1 × 2,2 × 2,3 × 2 and 3 × 3.A total of 21 groups of 63 push-out specimens are tested under monotonic loading and repeated loading.Observe its failure mode and describe test phenomenon.The results show that SFRC can effectively improve the crack resistance of the connector,and the rubber-sleeve can significantly improve the early slip and the recovery of slip under repeatedload.(2)Based on the test data,study the influence of volume fraction of steel fiber,concrete strength,diameter of stud,height and thickness of rubber-sleeve on shear capacity,peak slip and shear stiffness of SFRC stud rubber-sleeve shear connector.The results show that the shear capacity of SFRC stud rubber-sleeve shear connector increases with the increase of concrete strength,and the growth rate shows a slow trend;the shear capacity has a linear relationship with the sectional area of the stud and the volume fraction of steel fiber;the load patterns and the rubber-sleeve layout have little influence on the bearing capacity and the failure modes,but when the height of the rubber-sleeve exceeds 1/2 of the height and thickness exceeds 1 / 4.4 of the diameter of the stud,the shear capacity decreases by 9.2% and 15.8% respectively.The peak slip decreases with the increase of the volume fraction of steel fiber and the strength of concrete,and increases with the increase of the diameter of stud,and the rubber-sleeve greatly improves the peak slip of the connector.The shear stiffness increases with the increase of steel fiber volume fraction,stud diameter,concrete strength and elastic modulus.The rubber-sleeve effectively reduces the shear stiffness of the connector.When the thickness of the rubber-sleeve no less than 1 / 8.8 of the diameter and the height of the rubber-sleeve no less than 1/4 of the height of the stud,the shear stiffness of the SFRC stud rubber-sleeve shear connector decreases by 43.9% and 44.6%,respectively.(3)Based on the theoretical analysis and experimental research,referring to the existing and literature results,using non-linear fitting,obtained design formulas for the shear capacity and shear stiffness of the SFRC stud rubber-sleeve connector.The design formula of the shear capacity is suitable for SFRC rubber-sleeved stud shear connector with SFRC compressive strength grade which ranges from CF30 to CF60,and stud shear connector with the diameter of 13 mm to 25 mm,with the volume fraction of steel fiber less than 1.6%,with the thickness of rubber-sleeved smaller than1/2.6 diameter of the stud.The design formula of shear stiffness is suitable for the SFRC stud rubber-sleeve shear connector with SFRC compressive strength grade which ranges from CF30 to CF60,stud the diameter of stud between 13 mm to 25 mm,and the volume fraction of steel fiber less than 1.6%,the thickness of rubber-sleeved no less than 1/8.8 diameter of the stud and the height of rubber-sleeved no less than one quarter of the height of the stud.Besides,in order to obtain the higher shear capacity of SFRC rubber-sleeved stud shear connector in engineering design,theoptimal volume fraction of steel fiber is 0.8%. |
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