Study On The Seismic Perfomance Of High-strength Concrete Columns With Central Reinforcement And Corresponding Frame Structures

High-strength concrete has both high compressive strength and durability, which cancause significant decrease in the cross sections of columns and self weight of a structure, andavoid or reduce the phenomenon of “large column cross scections with slight reinforcement”due to the restriction of axial compression ratio of columns in an ordinary concrete frame.But its low plasticity hinders the extent of its application in seismic zones. Thoughconcrete-filled steel tubes and steel reinforced concrete can improve the deformation capacityand ductility of high-strength concrete, they have such disadvantages as high steel ratios, poorfire-proof property, complex joint detailing and construction difficulties, etc.. High-strengthconcrete columns with central reinforcement (HCCCR) are columns made of high-strengthconcrete with additional longitudinal bars provided at the central parts of their cross sectionscombined with composite ties to form the cores. This type of columns has both higher axialcompression capacity and ductility. There have been, however, rare literatures in the researchof HCCCR home and abroad, which makes their direct application inconvenient. In thisdissertation, the seismic performance of HCCCR has been investigated through theoreticalanalysis, test study and numerical computation so as to provide theoretical basis for theextensive application of such columns in actual projects.The major works and results includes:1) pseudo-static tests were conducted for7specimens of HCCCR under high axial compression and repeated lateral loading, with theirfailure phenomena analyzed and investigated, together with the lateral load carryingcapacities, hysteric property, ductility factor, strength and rate of rigidity degradation. It hasbeen indicated that HCCR has good seismic performance, which are affected by core area,core longitudinal reinforcement ratio and tie characteristic value;2) on the basis of testingdata, the dimensionless skeleton curves of HCCCR under repeated lateral loading were fittedand the basic parameters for simplified trilinear models were obtained; formula of theskeleton curves were put forth by using the methods of theoretical analysis and regression;based on hysteric rules of specimens, the restoring force model of HCCCRs was constructedand checked by the testing data;3) with the application of a finite element software,numerical analysis was conducted for a large number of HCCCRs with different parameters so that the rules were summarized by which core area, core longitudinal reinforcement ratio,characteristic value of tie and axial compression ratio affect the seismic performance ofHCCCRs. Analytical results shows that theoretical results closely match the testing results sothat it is feasible to use the finite element software to analyze the seismic performance ofHCCCR;4) for a7-storey concrete frame structure with its columns from the first to thefourth storey replaced by HCCCRs, both static elastoplastic analysis and dynamicelastoplastic analysis were conducted, and its seismic performance was comprehensivelyevaluated in terms of performance points, maximum inter-story drift angles and mechanismof appearance of plastic hinges. The study indicates that with reduction in the cross sectionsof ordinary concrete columns and increase in the utility rate of building areas, HCCCR canstill have equivalent, even better seismic performance as compared with the originalstructure.The research results can not only provide reference for the supplementation andperfection of seismic design codes, but can also form a sound base for the generalization andwide application of HCCCR.