Fatigue Behaviour Of Welded T-joints Of Concrete Filled Circular Hollow Sections

Welded Circular-Hollow-Section composite joints are widely used inconcrete-filled steel tube arch and space truss bridges in China. Fatigue behavior ofthese concrete-filled joints under daily vehicle load is very important problem thatneeds to be investigated. However, there is seldom similar structure for reference anddesign specification to guide now, and it is difficult to resolve it in theory. The studyof this paper is part of a research project of National Science Foundation Finance andis the study on fatigue behavior of welded T-joints of concrete filled circular hollowsection.There is a lot of design methods about the fatigue behavior of welded joints ofsteel tube, such as nominal stress method,hot spot stress method,fracture mechanicsmethod. Firstly, some introduction and comparison of those methods are carried out.Secondly, brief introduction about static loading experiment of welded T-jointsof concrete filled circular hollow sections is introduced. The purpose of staticexperiment is to get the stress concentration factor of joints under the axial force.Based on the measured stress concentration factor, hot spot stress is calculated.Fatigue experiments are performed on Eleven T-joints under axial tension force.Before the experiment, non-destructive detection is carried out, for evaluating thewelded deficiency to fatigue behavior of the joints. During the experiment of eachjoint, 24-hours monitor is carried out, for detecting the initiation and propagation ofcracks at weld toes in the intersection of joints.In the finally, based on the data measured in the experiment, S-N curve about thewelded T-joints of concrete filled circular hollow sections is obtained by linearregression analysis. The obtained S-N curve is compare to the exist S-N curveprovided by CIDECT,AWS,API,DnV.