Lanhui Guo

Behavior of Steel Tube and Confined High Strength Concrete for Concrete-Filled RHS Tubes:

This paper presents an experimental study of the separated behavior of short (L/H=3) high strength concrete-filled rectangular hollow section (RHS) tubes concentrically loaded in compression to failure. A total of 50 specimens were tested. Experimental results showed that the concrete strength influenced the failure pattern of the specimen. The height-to-breadth ratio of the rectangular tube (varying from 1.0 to 1.6) had no evident influence on the ultimate bearing capacity of the specimen. Then based on the experimental results, a numerical separation method was successfully used to separate the compressive load carried by the steel tube and the core concrete. The equivalent One-Dimensional nonlinear stress-strain models of the steel and the confined concrete were suggested, which can be used to determine the overall behavior of the high strength concrete-filled RHS tubes. The stress-strain models have been used to numerically analyze the behavior of high strength concrete-filled RHS tubes. The numerical results are compared with the experimental results and they agreed well with each other.

Behaviour of High Strength Concrete-Filled Slender RHS Steel Tubes

An experimental study of the behaviour of high strength concrete-filled slender rectangular hollow section (RHS) tubes under the combined actions of axial compression and bending moment is presented. A total of 26 specimens were tested. The main parameters considered in the test were slenderness ratio, depth-to-breadth ratio, steel-to-concrete area ratio and eccentricity-to-depth ratio. The experimental results showed that the ultimate capacity of test specimens decreased rapidly with increase of slenderness ratio and eccentricity-to-depth ratio. For the specimens with depth-to-thickness ratio larger than 50, local buckling failure occurred prior to the ultimate capacity. A nonlinear analysis program, BC, was developed to analyze the behaviour of high strength concrete-filled RHS tubes. A comparison for ultimate capacity showed that the theoretical results agreed very well with the experimental results. The depth-to-breadth ratio (varying from 1.0 to 1.6) showed little influence on the stability capacity of the specimens. The comparison of the experimental results with the results calculated by the design equations in the codes, such as LRFD, EC4 and AIJ showed that EC4 closely predicts the ultimate capacity of the specimens.

Experimental Study of Concrete-Filled Rectangular HSS Columns Subjected to Biaxial Bending

This paper describes the experimental work on the tests of nine concrete-filled square and rectangular hollow structural section (HSS) columns subjected to axial load, uniaxial bending or biaxial bending. The experimental results suggest that the overall buckling appears accompanying with local buckling near the mid-height of column. Good agreement was found between the semi-sine wave shape and the experimental deflection shape. It is found that the cross-section remains plane before the specimen reached its load-carrying capacity. Also, the experimental results are compared with the values calculated from the AISC-LRFD, EC4 and CECS design codes, which shows that all codes provide safe bearing capacities. Compared with columns subjected to an axial load or uniaxial bending, the calculated capacities of column subjected to biaxial bending are more conservative. Among these three design codes, the capacities based on the EC4 design code yield results which are the closest to the experimental ones. The results calculated from the AISC-LRFD design code are the most conservative.