Fatigue Cumulative Damage Model And Fatigue Life Prediction Of PBH Shear Connector

Based on PBL shear connectors,the research group put forward a new type of shear connector:a new type of open-hole stiffener ferrule shear connection structure(Perfobond Hoop,abbreviated as PBH).with the support of the National Natural Science Foundation Project "Research on the force mechanism and fatigue performance of PBH shear connector of steel box-concrete composite Structure"(51308571),the group to carry out the fatigue damage model of PBH shear key and the fatigue life research,main research contents and conclusions are as follows:1.Comparing PBH shear connectors static launch test and fatigue test of the test phenomena and laws.Two kinds of load form when the failure mode and shear stiffness of PBH degressive form and failure law of development and so on all have obvious difference.Static damage in concrete tenon fracturing,fatigue damage of concrete tenon crushed into powder,and two types of interface slip value is put in bigger difference;Two curves interface slip for development regularity is obvious different:fatigue slip curve is divided into three stages,static load sliding curve is divided into two stages;Static damage in the process of sliding curve lines smooth,no mutations,in the process of fatigue damage in the life of two mutations from 10%and 90%.2.PBH shear connectors of the finite element fatigue analysis.Tenon analysis found that the concrete in the process of loading,the contact area of steel and concrete in the local stress concentration;The development of the cracks in concrete tenon PBH shear key can be divided into stages of crack initiation and crack development stage.3.Completed PBH shear key fatigue damage mechanism research,studies show that the fatigue damage process according to the different failure mechanism is divided into three stages:initial steel composite interface bonding failure stage,mid tenon of concrete crush,migration stage and late stage;Early damage to the steel surface of the cement gel weak chemical bond destruction.medium-term damage to the initiation and development of fatigue cracks in concrete tenon will concrete segmentation,crush,structure within the cavity between the concrete powder migration result in slow slip of steel and concrete interface;Late damage is through reinforced by shear force of the perforated plate is bigger,through a large ring around a steel bar to tensile stress,crack development,structural stiffness is reduced,the specimen fatigue failure in the end.4.PBH shear connector stiffness degradation is divided into three stages,the initial interface bond destruction,of the division of the middle of the concrete tenon crush,later through reinforced concrete cracking.According to the theory of double linear fatigue cumulative damage theory,the first stage is simplified to a diagonal line,then draws the whole stage of the fatigue damage of fatigue damage model equation,and each cycle loading amount of damage.5.Analysis of fatigue test load ratio and the measured fatigue life curve of the specimens,PBH fatigue life and the load ratio relation is presented.In PBH shear key fatigue damage evolution equation is proposed in this paper,based on the load ratio is established after a given number of circulating load of fatigue damage,it is concluded that the remaining any,thus calculated PBH PBH fatigue life analysis methods of residual life.