Behavior of Square Concrete Column Confined with CFRP Sheets

I. INTRODUCTION:

Concrete is one of the most important materials for infrastructure development because of its wide range of applications; globally, it is second only to water in terms of utilisation. Concrete is one of the most common building materials. Concrete has evolved as a material and technology since its inception. There has been a constant search for improving the qualities of concrete due to the increased demands for performance and durability. Concrete is the most adaptable building material, and it is utilised in a wide range of civil engineering projects and structural parts all over the world. For a variety of reasons, concrete is the most extensively utilised engineering material. For starters, concrete is extremely water resistant. Concrete's resistance to some abrasive waters is to blame for the fact that it has been used in a variety of harsh industrial and natural conditions. The ability of structural concrete elements to be moulded into a range of shapes and sizes is the second reason for its extensive use. This is due to the fact that freshly mixed concrete has a plastic consistency, allowing it to flow into prefabricated formwork. Concrete's appeal among engineers is due to the fact that it is usually the cheapest and most easily available material on the job. Portland cement and aggregates are the main elements in concrete, both of which are very inexpensive and widely available in most parts of the world.

II. MATERIAL PROPERTIES:

A. Cement: Ordinary Portland 43grade cement was used in the experiment. Hydraulic cement was tested according to IS: 40311988 guidelines. Table 1 summarises the findings. B. Fine Aggregate: Fine aggregate is defined as material that can pass through a 4.75 mm IS sieve, as defined by IS: 383—1970. Sand size aggregate is another name for it. Fine aggregate was made from locally accessible C. Coarse Aggregate: In this project, crushed granite aggregates with a size of 20 mm are employed. To determine the specific gravity and fineness modulus of coarse aggregates, tests are carried out. The results of the tests are listed in Table-1.

D. Water: Concrete must be made with water that is free of sewage, oil, acid, strong alkalis, or vegetable matter, as well as clay and loam. The water utilised is safe to drink and can be used in concrete. Casting and curing of concrete specimens utilised in the experimental work are done with tap water provided by Sri Sunflower College of Engineering and Technology. E. Reinforcing Steel: In the case of reinforced columns, mild steel bars with a yield stress of 415MPa were used for longitudinal and transverse reinforcement. F. Carbon Fibers and Epoxy Adhesive: The carbon fibre utilised in this investigation is known as "Nitowrap" and is widely accessible on the market.

G. Super Plasticizer: Super plasticizers are a type of water reducer that is chemically distinct from regular water reducers and

The current study used concrete mixes with specific characteristic strengths of M 20, M 30, and M 40 MPa made with locally available ordinary Portland Cement (OPC), crushed granite jelly (20 mm down), river sand, and Glenium B233. The mix designs for these three concrete classes are based on IS 102622009 guidelines. The compressive strength of the concrete was measured using standard cubes (150mmX150mmX150mm). The mix proportions are decided based on the test results from a number of trial mixes.

The effect of wrapping CFRP sheets to the concrete column to increase axial load carrying capability for different grades of concrete is described in this research.

M20RC

M30RC

M40RC

Graph 4: Axial load v/s axial Shortening for Two Layers CFRP Strengthened Column

• The CFRP-strengthened column with up to two layers is effective in boosting the column's axial load carrying capability; nevertheless, the CFRP layers deemed ineffectual. • Column ductility is increasing as a result of the use of reinforcement and carbon fibre wrapping; ductility increases as the number of layers increases. • Tensile rupture of the CFRP jacket failed one-layer strengthened columns, while delamination and rupture of the CFRP jacket failed two-layer stronger columns, and simply delamination of the CFRP jacket failed three-layer strengthened columns. • When compared to a plain column, the RC column has a 36.37 percent improvement in load carrying capacity. • When compared to plain columns, one, two, and three layers strengthened columns enhance load carrying capacity by 96.64 percent, 126.02 percent, and 103.49 percent, respectively. • When compared to RC columns, one, two, and three layers reinforced columns enhance load carrying capacity by 43.04 percent, 63.82 percent, and 48.04 percent, respectively. • The toughness index of carbon fibre wrapped columns rises as the concrete grade rises and the number of CFRP sheet layers rises. • Proposed analytical models (Theriult and Neale, 2005) indicate reasonable wrapped column axial load capacities. • A plain column covered in one layer carbon fibres has 43.04 percent greater axial capacity than a R.C column. As a result, R.CC column can be replaced with a wrapped plain column. • When comparing the stiffness of two and three layer wrapping specimens to one layer wrapping specimens, RC, and plain column, the stiffness of two and three layer wrapping specimens is found to be the highest. • A two-layer plain column made of M40 grade concrete performs better in every way.

Y.Xio, H. Wu (2000), ―Compressive behavior of concrete confined by carbon fiber composite jackets‖, journal of material in civil Engineering, Vol 12, pp. 139-146. King Hwee Tan (2002). ―Strength enhancement of rectangular reinforced concrete columns using fiber reinforced polymer‖, journal of composite for construction, Vol 6, pp. 175-183. M. Reza Esfahani, M. Reza Kianoush(2005)., ―Axial compressive strength of reinforced concrete columns wrapped with fibre reinforced polymers‖, Vol. 18, No. 1-11. Lei Ming Wang, Yu Fei Wu (2007)., ―Effect of corner radius on the performance of CFRP confined square concrete columns‖, Engineering structures, Vol. 30, pp. 493-505. Hegde, R. R Dahiya, Kamath, M.G.(2004)., ―Carbon fibers.‖ N. Chikh, M. Gahmous, R. Benzaid (2012)., ―Structural Performance of High Strength Concrete Columns Confined with CFRP Sheets‖, Proceedings of the World Congress on Engineering, Vol. 3. Manuel A.G. Silva (2011). ―Behavior of square and circular columns strengthened with aramidic or carbon fibers‖, Construction and building materials, Vol. 25, pp. 3222-3228. A. R. Rahai, P. Sadeghian, M.R. Ehsani (2008)., ―Experimental behavior of concrete cylinders confined with CFRP composites‖, 14th world conference on earthquake Engineering. IS: 10262-2009 recommended guidelines for concrete mix design. IS: 456-2000 Plain concrete and reinforced concrete code of practice.

PG Student-Civil Engineering Department, SVERI‘S College of Engineering, Pandharpur, Maharashtra