Study On Seismic Performance And Design Method Of New High-strength Concrete Composite Columns

Reinforced high-strength concrete columns with embedded pipe and steel reinforcedhigh-strength concrete columns with rectangular spiral stirrups (hereinafter called newhigh-strength concrete composite columns) are new composite members, formed byhigh-strength concrete columns with different strengthening measures of composite ordinaryhoops and PVC pipe or steel tube, rectangular spiral stirrups and steel. This member canenhance confinement effect for core concrete, improve brittleness of high-strength concrete,and increase deformation capacity to meet ductility demand. It can be seen that newhigh-strength concrete composite columns have a good application prospects. Throughexperimental research, theoretical analysis and finite element simulation, the seismicperformance and design method of new high-strength concrete composite columns wassystematically studied in this dissertation.Utilizing good quality locally-produced raw materials, high-strength concrete with wellworking performance was mixed with construction technology of rational cement water factor,mineral admixture and admixture water reducing agent. Experimental and theritical researchwas carried on the basic mechanic behavior and stress-strain model of high-strength concrete.Twelve steel reinforced high-strength concrete(SRHC) columns with rectangular spiralstirrups, three reinforced high-strength concrete short columns with embedded PVC pipe(PVC-RHC), one reinforced high-strength concrete short column with embedded cricularsteel tube(CST-RHC) and one contrastive specimens of reinforced high-strength concreteshort column confined by ordinary hoops(RHC), respectively were tested under low cyclic reversed loading. The failure process, failure pattern, deformation capacity, energy dissipationand hysteric behavior of new high-strength concrete composite columns were studied, theeffects of design paramenter such as shear span ratio, axial compression ratio, concretestrength, volumne ratio of stirupps, strirupps configuration, heigh-diameter ratio of PVC pipeon bearing capacity, stiffness, ductility, energy dissipation were analyzed. Results show thathigh-strength concrete columns confined with embedded PVC pipe, cricular steel tube andsteel have better seismic performance than high-strength concrete column confined withordinary hoops.Based on test results, the influence of all design parameters on the shear bearing capacityof new high-strength concrete composite columns was analyzed. According to the straindistributed situation of longitudinal reinforcement, stirrups, PVC pipe, steel tube and steel, themechanical mechanism of different failure modes of columns was studied, the simplifiedmechanical model corresponding to failure modes was established and the calculationformulas of shear bearing capacity of new high-strength concrete composite columns wereproposed. The reliability of the calculation formulas of shear bearing capacity was verifiedthrough well agreement bettween calculated results and test results.Based on balanced failure between compression failure and tension failure, the limitvalues of axial compression ratio of normal reinforced high-strength concrete columns,CST-RHC columns and SRHC columns confined with rectangular spiral stirrups were derived.The limit values of axial compression ratio considering striupps, peripheral longitudinalreinforcement, dense longitudinal reinforcement core column were also given, which can beadapted to other strengthening high-strength concrete columns. The comparison betweenexperimental results and calculation results shows that calculation result using theaccumulative method is more accurate. According to the beneficial effect of steel ratio andvolumne ratio of stirupps, the limit values of axial compression ratio for shear compressionfailure SRHC columns confined rectangular spiral stirrups were given.The static elasto-plastic behavior of new high-strength concrete composite columnsunder the horizontal loading was simulated in ABAQUS. It was verified through wellagreement bettween calculated results by ABAQUS and test results. Based on the FEM model,the influence rule of shear span ratio, axial compression ratio, concrete strength, heightdiamenter ratio of tube, steel yield strength and steel ratio on the behavior of new high-strength concrete composite columns was obtained.Referring the current codes at home and abroad, five performance levels are presentedfor reinforced high-strength concrete frame, reinforced high-strength concrete frame withembedded cricular steel tube and steel, which are noraml service, temporary service, reparableservice, life safety and collapse prevention. Based on the results of seismic performanceexperiments at home and abroad, the limit values of inter-story drift angle corresponding todifferent performance levels are put forward for reinforced high-strength concrete columns,reinforced high-strength concrete columns with embedded cricular steel tube and steelreinforced high-strength concrete columns.