Test Sduty On Seismic Behavior Of High Strength Concrete Columns With Butt-welded Closed Composite High Strength Stirrups Under High Axial Compression Ratios

In order to achieve the performance based seismic design for high strength concretecolumns with butt-welded closed composite high strength stirrups(BCCHSS) underhigh axial compression ratio.9high strength concrete columns with BCCHSS. and1comparison specimen tested with quasi static. Failure process, failure modes,reinforcement strain curve, Angle of shear deformation in the plastic hinge region,hysteretic behavior and energy dissipation capacity and so on were studied. Theinfluence of axial compression ratios, transverse reinforcement volume ratios andarrangement of confinement reinforcement on hysteretic curves, skeleton curves,rigidity, bearing capacity and ductility of specimens were analyzed. The characteristicpoints parameter, angle of displacement, displacement ductility factors and energydissipation factors of all specimens have also been calculated. At the same time, theresult of the test were compared and analized with the result of finite elementcalculation. A restoring force model of columns is proposed, which considered theeffect of axial compression ratio and stirrup ratio. hysteretic rules were estimated.Empirical formulas of characteristic parameters in theoretical skeleton curve inhysteretic curve were put forward.The test results showed that: The ultimate failure modes for all properly testedcolumns are inverted triangle flexural failure; Shear deformation in the plastic hingeregion is not obvious, so the impact on the bending deformation can be ignored.Under the high axial compression ratio, the characteristic of energy dissipation are allgood, the hysteretic curves are all full with no obvious shrinkage phenomenon. Andunder high axial compression, with the axial compression ratios increasing, theenergy dissipation capacity was decrease, and the descending parts of the hysteresisloops were steeper, the characteristic of ductility is quite worse; With the increase instirrup ratio, the energy dissipation capacity changed for the better, and the slopes ofthe descending parts of the hysteresis loops were gently, the characteristic of ductilityis very well; Compared with comparison specimen, the confinement，the energydissipation，and the ductility of high strength concrete columns with BCCHSS was better. The results of hysteretic curves and skeleton curves were agree well with theresult of the finite element calculation. It can be seen that, they all can well donate theseismic behavior of high strength concrete columns with BCCHSS under high axialcompression ratios. Lastly, The skeleton curves of the proposed restoring force modelwere already indicated well with the test which verified the exactness of proposalrestoring fore model. This provided some reference for elastic-plastic seismicresponse analysis of new pattern steel-concrete composite structure with BCCHSSunder high axial compression ratios.