Hong Yu Zhou

Rate Correlation Research Situation of Ordinary Concrete about Strain-Rate within the Scope of the Earthquake

Combined with the research of dynamic mechanical properties of concrete under earthquake action by lots of scholars home and abroad, research status of rate-dependent test within the scope of the Earthquake strain rate (10-4/s~10-1/s) on common concrete materials is reviewed, including the dynamic uniaxial compressive properties, dynamic uniaxial tensile properties, as well as multi-axis dynamic performance. The influence of the Earthquake strain rate on concrete strength, energy absorption capability and deformation capacity such as the elastic modulus, Poissons ratio, peak strain, and ultimate strain are discussed intensively. Results show that the tensile strength, compressive strength and energy absorption capability of concrete increase with the increase of strain rate, while the results of the various parameters of the deformation ability are not consistent, the reason is that different test results caused by different test conditions. In this paper, the reference for the further study on rate-dependent of concrete in the future is provided.

Research Status of Fatigue Damage Mechanism of Reinforced Concrete Beam

Based on the fatigue damage mechanism, fatigue life, stiffness degradation, crack width change, bending, shear fatigue properties and other aspects, this paper introduces the research progress of the fatigue properties of ordinary reinforced concrete beams. And the existing reinforced concrete beam flexural, shear fatigue properties of research ideas, methods and results are summarized, providing the basis for further study on the fatigue performance of reinforced concrete beams. At present, the research results show that the fatigue damage of reinforced concrete beam is basically in accordance with the law of the three stages. In the early stage of fatigue, the tensile concrete cracks and exits, and the damage develops rapidly. In the middle of fatigue crack growth, fatigue damage is developed into a more moderate linear growth. In the late stage of fatigue, fatigue fracture occurs in the steel bar, and the bearing capacity of the beam is quickly lost.

Test Study on Size Effect Characteristics of Mechanical Performanceof Pure Bending Plastic Hinge in RC Members

Studies on size effect of plastic hinge of RC members are still rare at the present stage. This paper explores the development and failure characteristics of plastic hinge of pure bending section and analysis relevant mechanical parameters of size effect. Measured tests data show that plastic hinge equivalent length is close to the depth of beam which has no obvious size effect. However, plastic rotation capacity of plastic hinge has a significant size effect. Plastic rotation capacity decreases with section size increases if evaluate it based on ultimate load state, and increases with section size increases if evaluate it based on measured max load state.

Test Study on Bending Deformation Performance and its Size Effect Characteristics of RC Cantilever Beams

Studies on size effect around deformation performance of RC members are carried out relatively fewer at present. This article evaluated bending deformation capacity and size effect characteristics of RC cantilever beams by means of test method. And decomposed various deformation components with size effect factors considered, including bending, shear and bar-slip deformation and so on. The article focus on discussing bending deformation components at different loading stage and putting forward corresponding distribution functions. Calculation and experimental results show that bending deformation characteristics have significant differences on specimen dimensions, especially in nonlinear loading stage after longitudinal reinforcement yielding. Large size members have a significant concrete crushing process. ductility reserves show a growing trend with specimens size increasing. Bending deformation ability depends on average stiffness along overall beam before longitudinal reinforcement yielding. After plastic hinge forming, its bending performance will be decided by average stiffness within hinge region equivalent length.

Research Progress of Strain-Rate Effect on Mechanical Properties of Concrete

Introducing research progress of rate-dependent tests by domestic and foreign scholars, strain-rate effect on dynamic mechanical properties of concrete are reviewed. Classified descriptions of research results on dynamic load tests of concrete at home and abroad are provided, including uniaxial compression tests, uniaxial tensile tests, and multi-axis tests; strain-rate effects on concrete strength and deformation properties in each test are respectively discussed; and strain-rate effect on concrete energy absorption capability are described.

Nonlinear Analysis of Full-Scale Beam-Column Joints of RC Frames

In order to research on seismic performance of full-scale beam-column joints of RC frames under low cyclic loading, finite element software ABAQUS is used to nonlinear analysis. Analysis results show that: the process of load carrying and fracture development of beam-column joints are simulated using concrete damage plasticity model; nonlinear finite element method is easy to obtain stress-strain relationship; and can effective analyses the complex mechanical behavior of core areas of joints.

Test Study on Size Effect of Flexural Performance of RC Free Beams

Experimental studies on size effect of flexural behavior of reinforced concrete beams are not carried out fully. Standard values are based on test results of small-size components, which are different from large-size components in practical engineering. For size effect on quasi-brittle materials such as concrete, related researches have been carried out for many years, but related test study combined with concrete structures or components are not sufficient. This article is based on experimental study of 13 reinforced concrete free beams, obtaining test data during different loading stage, such as carrying capacity, deflection, steel and concrete strain etc. Test results show that size effect of flexural behavior of RC free beams is mainly reflected in reinforcement yielding stage and concrete crushing stage. The negative size effect due to concrete material is not significant. Yet internal force arm and longitudinal reinforcement have a positive size effect on flexural behavior, strength and ductility reserves show a growing trend with specimen size increasing. The safety of calculation theory of bearing capacity in code is verified indirectly.

Test Study on Size Effect of Flexural Capacity of RC Cantilever Beams

Analysis and calculation methods of reinforced concrete structure at present are based on test results of small-size component. This paper carried out test research on size effect of flexural capacity of RC cantilever beams. Sectional height of the biggest experimental specimen is 1000 mm. Obtaining detailed test data during different loading stage, such as carrying capacity, deflection, steel and concrete strain etc. Through observing test phenomenon and analyzing test data, verifying the safety to calculation formulas for ultimate bearing capacity of flexural members. Strength and ductility reserves show a growing trend with specimen size increasing.

Experimental Study on Size Effect of Flexural Capacity of RC Free Beams

Reinforced concrete calculation theories at the present stage are mainly based on experimental results of small size specimens, studies on the size effect of flexural capacity of large-scale reinforced concrete beam are not sufficient. Main research contents in this paper are the size influence on bending performance of under-reinforced beam, which can help to revise the related design theory. The paper collects test information of five different section size samples in different loading stage, including bearing capacity, deflection, section strain and so on. The total number of specimens is 13.Based on test failure process, development of cracks and deflections, analysis on section stress and strain, the safety of related bearing capacity formula is verified in research scale.It is also found that the safety reserve of calculation theory shows a trend of decrease with the specimen dimension increasing. As for large-size bending specimens, the code value of ultimate strain under non-uniform compression is bigger than test value.

Research Progress in Size Effect of Reinforced Concrete Members and Comparative Analysis of Applications of Codes

Abstract. Size effect, referring to mechanical properties of materials change with the geometry changes, is the basic characteristic of brittle and quasi-brittle materials. Researches show that for the concrete material, compressive strength, split tensile strength and tensile strength decrease with the size of components increases, for RC structures, size effect also exists. The development and current situation in size effect are presented from three aspects, including concrete, RC members and the application of the code. And then, the developing trends of size effect of RC members are proposed.