Out-of-plane Creep Buckling Analysis On Concrete-filled Steel Tubular Arches With Fixed Ends

Concrete-filled steel tubular arch bridge has been widely used in China in recentyears because of its high bearing capacity, long-spanning ability, convenient andeconomical construction process and attractive appearance. According to incompletestatistics, since the first CFST arch bridge has been built in1990in China, up to now,there are more than300CFST arch bridges in our country and the longest span is over500meters. The increasement of span would aggravate the out-of-plan creep bucklingproblem of CFST rib. The two kinds of creep buckling problem: the first kind is thatbecause of time effect, structure buckles under quasi-permanent load combination; thesecond kind is that strucure buckles under basic load combination (or incidental loadcombination). The two local standard of CFST bridge neither considers the problemo ofout-of-plan creep buckling. What is more, related study has just been started out andformular that can be used in reality is shorted of.This thesis will use ABAQUS to build finite model of circular section parabolaCFST arch and introduce modified EC2model and step-by-step method through UMATto consider time effect. Using Han Linhai’s consititutive model to simulate the nonlinearof material under high stress which can take restraint function into account. Usingnumerical method to verify the accuracy of UMAT in predicting long-term deformation.Through making a comparison between the outcomes of finite element analysis andexisted experiment, it proves the reliability of the modeling approch in analysing theout-of-plane stability of the arch.Analyzing the first and second kind of creep buckling problem based on the builtfinite model. Try to analyze the influence of different slenderness ratio, rise to span ratio,steel ratio, concrete loading-age and sthength of concrete and steel. Find out that steelratio and concrete loading-age are the mainly influencing factors for the first kind creepbuckling problem; steel ratio, sthength of steel and slenderness ratio are the mainlyinfluencing factors for the second kind creep buckling problem. Then extract creepbuckling decreasing coefficient formula based on the analysis above.At the same time, considering the pouring order concrete to analyze the effect ofdifferent slenderness ratio, rise to span ratio, steel ratio under different load. Throughthe analysis find out that considering construction process and time-effect at the same,the bigger the slenderness ratio, the lower the steel ratio, the higher the load grade, themore significant the effect will be. Moreover, after considering the constrution process,the CFST arch creep buckling decreasing coefficient will get smaller.