Study Of Ultimate Bearing Capacity For Dumbbell Shaped Concrete-filled Steel Tube Arch Rib With Initial Stress

The widely use of concrete-filled steel tube (CFST) arch bridges in countries around theworld has aroused great attention in engineering and academic field, and the research ofultimate bearing capacity has been developed and improved accordingly. However, theexisting researches on ultimate bearing capacity of CFST arch bridges almost just consideredthe influence of geometric nonlinearity or material nonlinearity only, without considering theimpact of initial stress. In order to study the influence of initial stress on the ultimate carryingcapacity of CFST arch ribs, the dumbbell shaped CFST arch rib which has been widelyadopted in practical engineering is taken as a research object in this paper, the theoreticalcalculation of ultimate carrying capacity is performed based on the unified strength theory byequivalent beam-column method, and a numerical analysis is carried out by using finiteelement analysis software ANSYS. The main contents in this paper are as followed:(1) Based on the unified strength theory and the revised equivalent beam-column method,the unified solution of ultimate bearing capacity for dumbbell shaped CFST arch ribs (bothwith initial stress and without initial stress) were deduced by considering the influence ofinitial stress and slenderness ratio. In addition, a new formula for influence coefficient ofinitial stress is obtained. The new formula is on the basis of the unified strength theory andcontains many factors. Through comparing the calculated results with that of experiments andother methods in the example analysis, the impact of initial stress on the dumbbell shapedCFST arch ribs is studied, the accuracy of all the computing methods is analyzed, theapplicability of unified strength theory and equivalent beam-column method for CFST archribs is discussed, and the rationality of the proposed method is proved.(2) Through using finite element analysis software ANSYS, the finite element model ofdumbbell shaped CFST arch rib is established with beam element, which supports the initialstress field. The double nonlinear finite element analysis of the whole stressing processes iscarried out and the ultimate carrying capacity, the failure mode and the mechanics mechanismare also researched for the CFST arch ribs (both with initial stress and without initial stress).(3) According to the theoretical and numerical analysis, the influencing characteristic of each parameter is analyzed. The result shows that the ultimate carrying capacity of dumbbellshaped CFST arch rib almost decreases linearly with the increase of initial stress, anddecreases nonlinearly with the increase of slenderness ratio. Additionally, the verticaldeformation of each section and the failure mode of the arch rib are all related to the formsand the function modes of the load.