Experimental Research On Stiffness And Strength Of Dumbbell-shaped Concrete-filled Steel Tubular Under Combined Compression And Bending

Dumbbell shaped concrete-filled steel tube arch rib get massively applied in engineering practice,the dumbbell shaped concrete-filled steel tube arch rib arch bridge accounted for as high as forty percent in concrete-filled steel tube arch bridge.Therefore,the mechanical properties of the dumbbell shaped concrete filled steel tube in-depth study has important engineering significance.At present,with dumbbell shaped cross section steel pipe concrete component test of related research is relatively small,at present has experienced the dumbbell shaped concrete filled steel tubular axial compression,pure bending,bias test,about the dumbbell shaped cross section bending test of concrete filled steel tubular components has not been carried out.In addition,the current research on concrete filled steel tube more focused on the ultimate bearing capacity,but less stiffness research.In terms of engineering design,besides bearing capacity limit state design artifacts,normal use limit state also been designed,therefore,dumbbell shaped concrete filled steel tube under the combined action of bending state at the external load to the research on the effects of stiffness is particularly urgent.In this paper,the influence of different axial compression ratio on the flexural capacity and flexural rigidity of dumbbell concrete-filled steel tube under the combined action of bending is studied and analyzed.The concrete work is as follows:(1)this paper summarizing bearing capacity of circle(party)concrete-filled steel tube bending stiffness and the related curve compression-bending capacity test and theoretical research status both at home and abroad;(2)according to the existing test data and conditions,for compression-bending test project design,conducting four different bending axial pressure ratio of dumbbell shaped steel tube concrete member composite test;(3)The effect of axial compression ratio on flexural rigidity and flexural capacity of members was analyzed by comparing the test results of four dumbbell shaped concrete filled steel tubular members under compression-bending composite effect.The experimental results show that:The initial bending stiffness and flexural bearing capacity increase with the increase of axial compression ratio when the axial pressure is relatively small(0～0.35),However,when the axial compression ratio exceeds 0.35,the initial bending stiffness and flexural capacity decrease with the increase of axial compression ratio.(4)Comparing the flexural stiffness,compression-bending capacity of the dumbbell-shaped concrete-filled steel tube under the influence of different axial compression ratios,and the existing specifications and the calculation results of the literature.The experimental results by comparison show that:The results of the existing standard bending stiffness formula are larger than the exper:imental value,while the N-M correlation curve equation is smaller compared with the experimental results.