Experiments And Researches On Unbond Prestressed Concrete Beams And Steel Reinforced Concrete Columns

The main contents of this thesis are the aseismatic performance and design theory of steel reinforced concrete structures and unbonded prestressed concrete structures. The whole thesis is divided into five chapters:(1) After summarizing and commenting substantive pertinent references and information, the factors influencing the performance of SRC structures and UPC structures were analyzed and the technical route was advanced.(2) Specimens of 16 unbonded prestressed concrete beams under low cyclic loading were tested. Deformations, curvatures, strains of the beams and the stress increments of unbonded prestressed tendons were measured and the crack distribution and failure models were observed. The bearing capability and ductility of unbonded partially prestressed concrete beams were deeply analyzed.(3) The static load tests of 18 steel reinforced concrete columns with different ratios of length to thickness under axial compression were carried out, which provide reliable grounds for the design of this kind of members. Eight steel reinforced concrete columns and four steel reinforced concrete combined frames were tested under low cyclic loading. The test data are of important values for guiding project designs and revising codes. The results of the tests indicate that steel reinforced concrete columns possess nice aseismatic performance. Furthermore a section design method for steel reinforced concrete components with eccentric compression, which is more simple and practical than the existing methods, was proposed.(4) Nonlinear analysis of the columns and the frames by using finite element method were executed. Considering the behaviors of unbonded prestressed concrete beams and steel reinforced concrete columns, a kind of nonconforming beam-column element was constructed and the analysis precision was improved. Loading and reloading paths were introduced into the constitutive relationship of concrete. It is helpful to the analysis program to trace the full-range mechanical behavior of structures including the descending part and the hysterisis characteristic under cyclic loading. For the solution of nonlinear equations, new viewpoint was presented. Compared with the test results, it is indicated the nonlinear analysis method in this thesis is feasible.(5) The reliability analysis of concrete columns under axial and eccentric compression was performed. For common reinforced concrete and steel reinforced concrete columns with axial compression, it is pointed out that the same stability coefficient can be adopted and closed reliability level can be provided. By combining Monte Carlo simulation and numerical calculation methods, the mean values and standard deviations can be obtained. And considering the relativity of axial force and bending moment of the loading effects, the reliability index of reinforced concrete and steel reinforced concrete columns with eccentric compression was calculated by the checking point method. Also all kinds of influencing factors were analyzed. It was observed that the reliability index of columns decreases along with the increase of steel amount,.as the steel amount reaches a certain value. When the axial force and bending moment of the loading effects are considered incompletely correlative or independent, the reliability index also decreases.