دانلود رایگان مقاله بتن پر شده فولاد بیضوی اعضای لوله با نسبت قطر بزرگ به ضخامت در معرض خمش

ABSTRACT

Concrete filled elliptical steel tubes, hereafter called CFESTs, are elliptical steel tube members filled in with concrete. The CFEST belongs to a family of concrete filled steel tubes, the so-called CFT, having good deformability and large seismic strength due to confined effect between the tube and in-filled concrete. The present study aims to investigate experimentally the characteristics of the CFEST members under pure bending. The selected testing parameters are diameter-to-thickness ratio of elliptical steel tube and loading directions, namely, the minor and major axes directions. From the test results, both local buckling and cracking of the steel tube can be observed in compressive and tensile regions, respectively. Obtained pure bending strength of the CFEST is strongly affected by diameter-to-thickness ratio. Pure bending capacity of the CFEST is also compared to that of the circular CFT. Methods to predict pure bending strength of the CFEST based on concrete strength, yielding and fracture points of the steel tube and confinement effect are described. Moreover, pure bending strength of the CFEST members is mainly discussed in comparison to that of ordinary CFT members. Additionally, biaxial stress behavior of the steel tube induced by in-filled concrete is also mentioned.

4. Conclusions

Concrete filled elliptical steel tubular (CFEST) members with large diameter-to-thickness ratio subjected to pure bending moment have been examined. Additionally, pure bending characteristics of the CFEST beams have been compared with that of ordinary CFT members. Considering two main testing parameters, diameter-to-thickness and two pure bending loading directions, namely, major and minor axes directions, the following conclusions can be drawn. (1) Observed failure modes were both local buckling in compressive region and fracture in tensile region of elliptical steel tubes. These phenomena agreed with the results for ordinary CFT member under pure bending. (2) Bending moment deformability increased as diameter-tothickness ratio (2a/t) decreased. Moreover, the smallest deformability was found in the CFT specimens with D = 160 mm, which are the smallest diameter. (3) Ultimate bending capacities (Mexp) of major, minor axis test specimens and CFT member with D = 80 mm were maintained for central displacement that were over 20 mm.