Composite Columns Steel Pipes With Square and Rectangular Sections and High-Strength Concrete Core

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Title: Composite Columns Steel Pipes With Square and Rectangular Sections and High-Strength Concrete Core

Author(s): J. F. Fernandez and R. S. Agostini

Publication: Special Publication

Volume: 186

Issue:

Appears on pages(s): 357-370

Keywords: columns (suports); composite column; compressive strength; high-strength concretes; steel pipes; structrual design

Date: 5/1/1999

Abstract:
High-strength concrete columns, usually reinforced, require high rates of confined transverse reinforcement to obtain ductile fracture. In this paper it the composite columns of steel pipes with square and rectangular sections, and cores consisting of high-strength concrete, are analyzed with the objective to of changing the usual confining reinforcement. The metal pipes were fabricated with steel plates with 5,0 mm and 6,9 mm thickness, on cold cutting and folded in "U" form, and then subsequently compounding pipes with transverse sections of 60mm by 60mm and 60mm by 100mm, and 460mm height. The wall cross-section of steel pipes was determined by section of transverse and longitudinal reinforcement used in the square and rectangular columns reinforced conventionally. In the design the differences between yield strain of steel plates and yield strain of the reinforcement concrete columns were computed. To define the yield of strain of steel plates, specimens were tested and analyzed under axial tension. With the mechanical properties of the metal pipes and the mixture o the high-strength concrete core, eight models were tested, four with square transverse section and four with rectangular transverse section. The specimens were tested under concentric compression loading, on a ridged hydraulic press with load controlled capabilities, having a maximum compression load of 10.000 kN. It is concluded from the investigation that composite columns with square section was efficient in the confinement of high-strength concrete columns with rectangular section presented, localized instability near the extremities probably due to compression of the concrete core.