Papers by Author: Zhi Gang Yan

Abstract: Further research on constitutive model of RPC (Reactive Powder Concrete) restrained by steel tube under axial compression is analyzed based on the research on concrete-filled steel tube and RPC-filled steel tube at home and abroad. Finite element analysis on RPC-filled steel tube stub columns under axial compression is conducted with ABAQUS to analyze the confinement index, core concrete strength and contact property on ultimate bearing capacity of RPC restrained by steel tube. As the confinement index and the core concrete strength increasing, the bearing capacity of RPC restrained by steel tube increases. The model with frictionless contact form has greater bearing capacity, but the ductility decreases.

Abstract: In recent years, Reactive Powder Concrete (RPC) has been concerned by the structural engineers and researchers. RPC is a kind of cement-based composite which has ultra-high strength, high ductility and durability, however, it has great fragility. The fragility performance of RPC will be improved if RPC and steel are put together as RPC-filled steel tube circular stub columns. The aim of this paper is to develop accurate finite element models to simulate the behavior of RPC-filled steel tube circular long columns. The finite element program ABAQUS is used in the analysis. An extensive parametric study is conducted to investigate the effects of different slenderness ratio and confinement action on the strength and behavior of RPC-filled steel tube circular long columns. The results obtained from the models are verified against the results of the tests. The results show that the rising part of load-strain curves are in good agreements with experiment results.

Abstract: Based on uniaxial tensile test, the complete uniaxal tensile stress-strain curve of Reactive Powder Concrete (the steel fiber content by volume is V_f =1%, 2%) was obtained, and the fracture energy of RPC specimens with cross-section of 100mm by 100mm was calculated. The test was finished through Universal Testing Machine without any stiffness-strengthen devices. In order to solve the stress concentration problem, a self-designed uniaxial tensile test equipment was developed, and a dumbbell-shaped specimen was used in the test. The results indicate that the fracture energy of RPC increased as well as the increasing of V_f.

Abstract: In order to study the mechanical performance of Reactive Powder Concrete (RPC) used for structure engineering, 38 series of RPC specimens are fabricated, cured, tested and analyzed. There are 5 sets of specimens are fabricated for each actual site structure engineering. The compressive strength, flexural strength and elastic modulus are tested according to the specimens and the compressive strength is tested with different age time. All the specimens are steam cured with the same situation as the structure. According to the test result, the compressive strength of RPC is up to 80MPa 3days after it is cast and the compressive strength is higher than 120MPa 15days later. The average flexural strength of RPC is 19.4MPa and the elastic modulus is 45.15GPa. The tested results show that the mechanical performance of RPC can satisfy the engineering requirement. The mixing proportion and the curing system can be used for engineering design and construction.

Abstract: Reactive Powder Concrete (RPC) is a new kind of building material with high strength and other good performance. The combination of RPC and steel tube will compensate the brittleness of RPC and enhance the stability of steel tube, and the loading capacity of the RPC filled steel tube will be improved. Five RPC filled steel tube columns are designed and tested to obtain the ultimate load bearing capacity, the deformation and the strain information. During the loading process, the concrete and the steel tube of the RPC filled steel tube columns are loaded simultaneously. The loading results show that the deformation of the RPC filled steel tube columns are mainly in elastic phase before the loading capacity is up to the ultimate value. The test load decreases to be 80%~90% of the ultimate loading value and then it changes to be smooth. The failure mode of the RPC filled steel tube columns is ductile. The test loading capacity is compared with the formula from the reference. The tested ultimate load bearing capacity of the steam cured RPC filled steel tube columns is higher than the calculated value. The calculated value is safe for the engineering application. The study is useful for the research and application of RPC filled steel tube column.