International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 02 | Feb -2017
p-ISSN: 2395-0072
www.irjet.net
Investigation on the Behaviour of Stiffened Concrete-Filled Double Skin Steel Tubes M. Thiruvannamalai1, S. Varun2 1Assistant
Professor, Dept. of Civil Engineering, Mepco Schlenk Engineering College, Tamilnadu, India Student, Dept. of Civil Engineering, Mepco Schlenk Engineering College, Tamilnadu, India
2Postgraduate
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Abstract - Numerical study on the behaviour of stiffened
and analysed with a square cross section for the outer skin in most specimens and a rhomboidal inner skin for a few (RCFDST and SR-CFDST). The specimens were tested for a hollow ratio of 0.46 and 0.5 with a wall thickness of 4mm and 8mm for a height of 800mm and 1200mm. Results imply that the effect of stiffeners improve the capacity of the column in few cases while the same trend is not observed in others.
concrete filled double skin steel tubes with a new arrangement of inner skin and stiffener are presented in this paper. Comparisons between stiffened and unstiffened concrete filled steel tubes (CFST and S-CFST), concrete filled double skin steel tubes (CFDST and S-CFDST) and rhomboidal inner core concrete filled double skin steel tubes (RCFDST and SR-CFDST) are made after analysing the axial capacities, their equivalent stress and strains. A total of 28 specimens were modelled and analysed based on the 1) hollow ratio (0.46 and 0.50); 2) Thickness of the skins (4mm and 8mm); 3) Height of the tubes (800mm and 1200mm); 4) Cross-section of the tube (square); 5) Length of stiffeners. 6)Width-to –thickness ratio of the inner and outer skins. Results imply that the effect of stiffeners is predominant in 800mm S-CFST unlike 1200mm S-CFST. In the case of CFDST for a hollow ratio of 0.46 the axial capacity increased for the stiffened specimens of both heights and decreased for specimens with a hollow ratio of 0.5. In case of RCFDST the axial capacities of stiffened specimens recorded lesser values than unstiffened specimens irrespective of the hollow ratio and height.
2. ABBREVIATIONS & ACRONYMS 8004 - 800mm height and 4mm wall thick 8008 - 800mm height and 8mm wall thick 12004 – 1200mm height and 4mm wall thick 12008 – 1200mm height and 8 mm wall thick P – Partial Length stiffeners F – Full Length Stiffeners – outside with of inner tube
Key Words: CFDST, Axial Capacity, Stiffened, FEA, Hollow Ratio
– outside width of outer tube – length of specimen
1.INTRODUCTION
– wall thickness of inner tube
Concrete–filled double skin steel tubes behave similar to concrete-filled tubes under the same dimensions and material properties. The prominent aspect of CFDST is its lighter weight when compared to CFST due to the absence of concrete in the core. By virtue of its lighter weight CFDST are useful in bridge piers, elevated corridors, buildings and towers. Studies show that columns with Smaller Width-toThickness ratio behave better [1]. Among the factors that affect the strength of the column, Slenderness ratio is the most significant [2]. The effect on ductility due to stiffeners by the increment in the inertia, hollow ratio has also been studied [6] [7]. Various studies have been conducted to comprehend the behaviour of concrete-filled double skin tubes subjected to torsion [8], fire performance, local bearing force yet the behaviour of CFDST is not aptly comprehensive compared to CFST. For the aforementioned condition it is essential to investigate its behaviour which can tremendously aid the design process. The aim of this investigation is to comprehend CFDST where our focus is on the axial capacity. A total of 28 specimens were modelled
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– wall thickness of outer tube – Buckling load χ – hollow ratio =
3.BOUNDARY CONDITIONS All the specimen lie on the X-Z plane. The X-Z plane is fixed at the bottom (θx= θy= θz= Ux= Uy=Uz=0) and the top is restrained against translation and rotation in all directions except Y (θx= θy= θz =Ux=Uz =0; Uy= Free).
4.MATERIAL PROPERTIES Concrete Density - 2400 kg/m3
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