Research On Seismic Performance And Design Calculation Methods Of Steel Reinforced Recycled Concrete Columns

The ordinary steel reinforced concrete composite structure has a high bearing capacity andgood seismic performance. At the same time, the recycled concrete can save energy andprotect environment, which has the characteristics of renewable utilization. Combined withthe above characteristics, the steel reinforced recycled concrete composite structure was putforward in this paper. The new structure not only can improve the earthquake resistanceability of building structure, but also accord with the strategies of national greenenvironmental protection and sustainable development. Therefore, the steel reinforcedrecycled concrete composite structure has a broad application prospects. In this paper, throughthe test and theoretical methods, the mechanical properties of steel reinforced recycledconcrete columns under low cyclic loading were researched in detail. The design calculationmethods of column were also put forward in this paper.According to the characteristics of recycled concrete and composite structure, the recycledconcrete materials which met strength requirements were designed and prepared. On theabove basis,17steel reinforced recycled concrete columns were designed and produced inthis paper. The design parameters mainly include recycled coarse aggregate replacement ratio,shear span ratio, axial compression ratio and stirrup ratio. Through the low cyclic loading test,the failure processes and modes of the columns were studied and the hysteresis curves andskeleton curves were also analysed in major. On that basis, the seismic capacity, stiffnessdegradation, strength attenuation, energy dissipation capacity, ductility and lateral angles ofcolumns were researched in detail. In addition, the impacts of design parameters on seismicperformance of steel reinforced recycled concrete columns were also researched.Combined with the characteristics of steel reinforced recycled concrete columns andsimplified processes, the OpenSees software was used for simulating the hysteretic behaviors of steel reinforced recycled concrete columns under low cyclic loading. The hysteresis curvesand skeleton curves of columns were obtained. The simulation results and test results werecompared, which verified the rationality of finite element analysis results. On the basis, theinfluences of recycled concrete strength grade, steel strength, steel ratio and stirrup strengthon seismic performance of the columns were analysed in detail.According to the hysteresis characteristics of steel reinforced recycled concrete columns,the restoring force model which is suitable for the columns was established in this paper. Themodel used the four line of stiffness degradation model which includes the skeleton curvemodel, stiffness degradation and hysteresis rules. Using the theories and statistical regressionmethods, the feature points including cracking point, yield point, peak point and limit point ofskeleton curve model were determined. Besides, the load stiffness and unloading stiffness ofrestoring force model were also given in this paper. The calculation skeleton curves and testskeleton curves were compared, which verifies the rationality of the restoring force model.On the basis of ductility coefficient, the test value of axial compression ratio which canguarantee the steel reinforced recycled concrete columns having a good seismic performancewere given in this paper. According to the limit compression damage theory of eccentriccompression columns, the calculation methods of limit value of axial compression ratio forthe bending failure columns were given and the limit values of axial compression ratio alsowere obtained combined with the test results. According to the relationship between the axialcompression ratio and ductility coefficient, the limit values of axial compression ratio for theshear failure columns were given. On the beneficial effect of stirrup ratio for the ductility ofcolumns, the limit values of axial compression ratio of steel reinforced recycled concretecolumns were provided under the different stirrup ratio in this paper.According to the test results, the horizontal bearing capacity of steel reinforced recycledconcrete columns was studied and analyzed the influence of design parameters such as therecycled coarse aggregate replacement ratio, shear span ratio, axial compression ratio andstirrup ratio on the horizontal bearing capacity of columns. On the basis of strain change ruleof steel, stirrup and longitudinal reinforcement in columns, the characteristics and mechanismof horizontal bearing capacity of columns were researched in detail. According to the stressmechanism characteristics of different failure modes of columns, the calculation formulas oftheir corresponding horizontal bearing capacity were given through the theoretical method. And the practical calculation formulas of horizontal bearing capacity for steel reinforcedrecycled concrete columns was also given in this paper.In accordance with the stress characteristics of steel, the calculation formulas of bondstress between steel and recycled concrete were given. The strain distribution of steel flangeswere obtained through the resistance strain gauges. Analysing the strain distribution laws ofsteel flanges and carrying out the multiple regression analysis for the strain distribution laws,the mathematical description curves of strain distribution of steel flanges were obtained.Through the derivation of the curves, the equivalent bond stress of steel flanges can becalculated by the above calculation formulas. The distribution rules and characteristics ofbond stress of steel reinforced recycled concrete columns were analysed in detail. Accordingto the degradation mechanism and characteristics of bonding in columns under low cyclicloading and combined with test results, the calculation formulas of bond stress degradation ofcolumns were given in this paper.Combined with test research, the earthquake damage characteristics of steel reinforcedrecycled concrete columns under low cyclic loading were analysed and the earthquakedamage of columns were quantitative processing through the test results. Based on theexisting seismic damage models and combined with the characteristics of columns, theearthquake damage model based on the nonlinear combination of deformation and cumulativeenergy dissipation for steel reinforced recycled concrete columns was established. Thecalculation damage indexes and test damage indexes were compared, which verifies therationality of the earthquake damage model for the columns. Finally, the influences ofrecycled coarse aggregate replacement ratio, shear span ratio, axial compression ratio andstirrup ratio on the earthquake damage performance of the columns were analysed detailedly.