Research On Mechanical Behaviors And Design Theory Of Steel Reinforced High Strength And High Performance Concrete Columns

As an optimized combination of high-tech concrete material and new-style composite structure, Steel reinforced high strength and high performance concrete (SRHSHPC) structure possesses excellent mechanical performance and seismic behaviour, which is applied to engineering more and more extensively. For design method theorizing perfectly, the mechanical performance and seismic behaviour of SRHSHPC columns are studied systematically by the way of combining experimental investigation, theoretical analysis and numerical simulation.(1) Based on the local materials and normal production techniques, selected well graded and quality raw materials, and mixed high efficiency water reducing agent and mineral admixture, the high strength and high performance concrete (HSHPC) applied to steel reinforced concrete (SRC) structure is invented by concrete nonlinear multiple objective optimization design which depends to the concrete orthogonal test. The mechanical performance, endurance and stress-strain constitutive relationship of HSHPC is studied systematically. Secondly, the bond-slip characteristic of steel and HSHPC is explored experimentally by 4 specimens. The load- slippage relationship curve at loading end is obtained. The longitudinal regularities of distribution of bond stress and slippage are analyzed and the reasonable equations are established too. The formula for limiting characteristic number of bond stress and slippage is presented by statistical regression analysis. The bond-slip constitutive relationship is established at last. Thirdly, the bond-slip behaviour of reinforcing bar and concrete, failure mechanism and influencing factor are analyzed whose bond-slip constitutive relationship is also provided. Finally, the bond-slip characteristic of steel and concrete is researched systematically at component level. The characteristic value of bond stress and slippage, and regularities of distribution in SRC columns which are subjected to eccentric compression and constant axial compression and cyclically varying horizontal load are analyzed detailedly. The bond-slip constitutive relationship of SRC column considering position function is presented eventually.(2) Based on experimental investigation for 4 SRHSHPC columns with eccentric compression loading, the loading performance of specimens is studied. The strength and deformation of specimen, stress-strain developing process for identifying the stress distribution of steel and concrete in column section are tested. Furthermore, failure mode and mechanical character for specimen are analyzed and the main factors which affect bearing capacity of columns are discussed. Secondly, according to the experiment analysis result, the flexural capacity calculation method for specimen is established which is based on modified plane section assumption and concrete equivalent stress graph. The calculation result agrees with experimental result well.(3) The seismic behaviour of SRHSHPC frame columns is investigated by the experiment of 16 frame column specimens subjected to constant axial load and cyclically varying flexural loading. The design parameters of specimens include shear span ratio, axial compression ratio, concrete strength, steel ratio and stirrup ratio. The study is focused on main seismic performance indexes of specimens which have different design parameters, such as mechanical character, failure mode, hysteretic performance, ductility and energy dissipation. Furthermore, the main factors which affect seismic performance indexes of specimens are discussed. The research result indicates that seismic behaviour of column is excellent, but it will decrease when the concrete strength and axial compression ratio are oversize.(4) The shear behaviour of SRHSHPC frame columns is studied experimentally. According to the test result, shear failure patterns of specimens are mainly three types: shearing compression failure, shear splitting failure and flexural failure mode. The shear strength of specimen, stress-strain developing process for identifying the stress distribution of steel and concrete in column section are tested. Furthermore, the shear mechanism for specimen is analyzed and main factors which affect shear strength of columns are discussed detailedly. Secondly, the bearing capacity calculation method for specimen which belongs to flexural failure mode is established which is based on modified plane section assumption and concrete equivalent stress graph. Based on axial compression force distribution ratio, the shear capacity calculation methods for specimens which belong to shearing compression failure and shear splitting failure mode are established by principle of accumulation. The practical shear capacity calculation methods are proposed finally. The study results indicate that the shear behaviors of SRHSHPC frame composite columns are excellent, and the calculated results of shear strength have good conformity with test results.(5) Based on choosing reasonably constitutive relation, failure criteria and crack processing modularity of HSHPC, the SRHSHPC columns which are subjected to eccentric compression loading, constant axial load and cyclically varying flexural loading, and monotone increasing horizontal loading, are simulated numerically by nonlinear finite element analysis program. At the same time, the bond-slip effect between steel and concrete is simulated by multi-directional spring element. Finally, comparison of load-displacement curve from FEM and experiment is presented.(6) The existing seismic damage models are concluded and analyzed. Furthermore, the damage indexes of SRHSHPC frame columns are calculated by applying typical double parameters seismic damage models. The validity of each typical damage model is verified for evaluating the damage evolution of specimen. Secondly, according to the damage experiment and accumulated hysteretic-energy analysis results, the double parameters seismic damage model for SRHSHPC frame column, which is based on combination of deformation and accumulated hysteretic-energy, is established reasonably. The parameters of model are also defined. The damage evolvement processes of SRHSHPC frame columns are evaluated by applying established damage model. The main factors affecting damage of specimens are discussed. Finally, the classification tables for structure performance levels and damage states are presented felicitously. The defined damage performance objective will supply reference for performance-based aseismic design of SRHSHPC structure.