by Click the blue word to pay attention to us LV Zhaohua, Wang Chaoyang, Zhang Jie, Fang Cheng Abstract: the quasi-static test of five cold-rolled round end elliptical steel pipe specimens with different axial compression ratio and bending direction is carried out, the hysteretic curves of each specimen are obtained, and their failure mode, yield / ultimate load, ductility and energy dissipation capacity are discussed.
Based on the test results, 1080 finite element models of elliptical steel tube compression and bending members with circular ends are established, the parameter analysis is carried out, and a practical seismic design method is proposed.
The results show that the local buckling of the column base leads to the failure of the specimens, and the local buckling failure modes of the specimens in different compression and bending directions are different.
In the test, the flat plate section of the steel pipe section buckles first and has stable post buckling performance.
Larger axial compression ratio will cause earlier local instability and more serious column bottom failure, resulting in the decrease of ductility of the specimen.
The section plastic bending moment of the specimen bending around the strong axis can be more fully developed.
The practical design methods based on ductility and bearing capacity are obtained by fitting the finite element model data with the least square and lower boundary curve.
Key words: circular end elliptical section; Bending members; Quasi static test; Hysteretic performance; Abstract: quasi static tests areastructureconfigurerehsbeam column specifications with different axial loadings and bending directions Thefailuremode，yield/ultimatestrength，ductility，andenergydissipation-relatedquantitiesarediscussed.
Anumericalstudyisthenconductedonatotalof1,080REHSbeam-columnmodels，andthecrosssectionandmaterialparametersarefurtherstudied.
Finally，thepracticalseismicdesignmethodforREHSbeam-columnsisproposed.
Basedonthisstudy，thelocalbucklingatthefixedbasegovernsthefailuremodeofREHSbeam-columns，althoughdifferentfailuremechanismsareobservedunderdifferentbendingdirections.
TheflatplatesectionoftheREHSismorepronetolocalbuckling，andhasstablepostbucklingperformance.
Whentheaxialloadratioincreases，anearlierlocalbucklingandmoreseveredamagetothecolumnbasecouldoccur，hencetheductilityiscompromised.
Whenthebeam-columnisundermajoraxisbending，theplasticmomentresistanceisbettermobilized.
Basedonthefiniteelementmodeldata，practicalductility-orientedandstrength-orienteddesignapproachesarefinallyproposed，andbothleast-squareregressionandlower-boundsolutionsareprovided.
Keywords：round-endedellipticalhollowsection（REHS）； beam-column； quasi-statictest； hystereticbehavior； Background with the development of construction industry, people have higher requirements for the shape and performance of building structures, and a new type of oval / oval steel pipe has also attracted extensive attention.
Among them, the standard elliptical section is usually called EHS (elliptic hollowsection).
The streamline shape of EHS steel pipe has the characteristics of beautiful architecture and small fluid load.
Compared with square and circular steel pipes, the bending stiffness of this kind of steel pipe section around the long and short axis of symmetry is different.
Reasonable design of section size can make full use of steel strength and provide visual perception from different angles.
In order to meet the market demand, cold-formed and hot-rolled oval / oval steel pipes at home and abroad are gradually realizing industrial production [1]..
