International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 05 | May -2017
p-ISSN: 2395-0072
www.irjet.net
ANALYTICAL STUDY ON CONCRETE FILLED STEEL TUBULAR COLUMNS WITH BFRP WRAPPING UNDER AXIAL LOAD Silgy Salim1, Pinky Merin Philip2 1PG Student, Civil Engineering, Saintgits College Of Engineering, Pathamuttom,Kottayam,Kerala,India. 2Assistant professor, Civil Engineering, Saintgits College Of Engineering, Pathamuttom,Kottayam,Kerala,India. ---------------------------------------------------------------------***----------------------------------------------------------------------
Abstract - Composite columns have been widely
used in the construction industry mainly due to its high strength, durability, ease of construction and cost saving. Concrete Filled Steel Tubular (CFST) columns combine the structural properties and advantages of both steel and concrete materials. As the steel tubes eliminates the need of formwork, it leads to accelerated construction and cost saving. The steel tube provides confinement to the concrete infill, which in turn acts as a support to the steel tube and prevents local inward buckling of the section. But these members can get deteriorated due to corrosion and ageing. New materials and strengthening techniques need to be introduced to combat this problem. Strengthening methods using fiber reinforced polymer (FRP) can eradicate the difficulties caused due to traditional strengthening techniques like section enlargement and external wrapping using steel plates. This paper aims to study the load carrying capacity of Basalt Fiber Reinforced Polymer (BFRP) wrapping in strengthening of CFST long columns under axial load by using ANSYS 17.0 (WORKBENCH) software. The modelling of CFST columns with BFRP wrapping were studied with variation in parameters such as spacing of sheets (20mm,30mm,40mm) and effect of fibre orientation. 0° and 45° angle orientation is provided for each variation in spacing of the FRP sheets. Key Words: Buckling, BFRP, CFST, Finite Element Analysis ,Strengthening.
1. INTRODUCTION The Concrete Filled Steel Tubular (CFST) columns are evolved as an alternative to the conventional techniques in the recent years .CFST members utilize the advantages of both steel and concrete materials. It comprises a steel hollow section of square, rectangular or circular shape filled with plain or reinforced concrete. Steel sections with concrete infill are being commonly used as structural members, because filling the steel section with concrete increases both its strength and ductility without increasing the section size. Researchers found that the CFST column system has many advantages compared with the ordinary steel or the reinforced concrete system due to its high-strength, stiffness, ductility, and better seismic resistance. Since steel confines the concrete, the use of formwork can be discarded. The © 2017, IRJET
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concrete and steel are combined in such a fashion that the advantages of both the materials are utilized effectively in composite column .The potential economical advantages of concrete-filled steel columns (CFST) in tall buildings could lead to significant savings of steel usage in comparison with pure steel buildings. The structural behavior of CFST members was mainly affected by the difference between the Poisson’s ratios of the steel tube and concrete core. In the initial level of loading, the Poisson’s ratio for the concrete is decrease than that of steel. Thus, the steel tube has no confining effect at the concrete core.
1.1 Fiber Reinforced Polymer(FRP) Fiber reinforced polymer is composed of fibers embedded in a resin matrix, and is characterized by its high strength-to weight ratio, high corrosion resistance, and ease of installation. It is well known that FRPs have limited fire resistance because of the low glass transition temperature of their epoxy resins. FRP material in itself is a composite that consists of fibers, which are chosen from a wide range of materials such as carbon, aramid and glass, which reinforce the polymer matrix. Some of the materials used for the polymer matrix are polyester thermosetting plastic, epoxy and phenol formaldehyde resins. The FRP material composes of mainly four elements. First, the reinforcing fibers are used to carry and withstand all the applied loads and stresses. Second, the resins are added to allow for load transformation among the fibers in addition to gluing these fibers together and shielding environmental effects. Third, the modifiers are additives to enhance the polymers performance and to increase its lifetime. Fourth, the fillers replace the unneeded resin in the composition and to control the final product’s shrinkage as well as increase its cracking resistance. The basalt fiber is now being a popular choice for the material scientists and research fellows for the replacement of carbon fiber and steel due to its high stiffness, low cost and low elongation at break. Basalt is a material made from extremely fine fibers of basalt which constitute the minerals include plagioclase, pyroxene, and olivine. Basalt of high acidity (over 46% silica content) and low iron content is considered desirable for fiber production .Compared to carbon and aramid fiber ,it has higher oxidation resistance ,higher radiation resistance, higher shear strength.
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