Study on PSWC-bar as Reinforcement for Beam

Abstract

Majority of steel reinforcement that we use in practice has surface having lugs or protrusions. They are used to increase the bond capacity between the rebar and the surrounding concrete. In order to achieve increased bond strength and to stop reinforcement slippage of HYSD steel bars, protrusions were introduced on the surface of the straight Mild steel bars. Plain surface with wave type con guration bar is known as PSWC-bar. The PSWC-bar is characterized by its plain surface and a gently undulating wave-type con g- uration. PSWC-bar is the new name of C-bar. A comprehensive experimental programe with 24 numbers of beams, involv- ing PSWC-bars (with 4mm, 5mm & 6mm o set), plain bars and HYSD bars with various grade of steel(Fe 415, Fe 500, Fe 500 D, Fe 550 D), are under- taken in the present study. Breakup of these con gurations is as follows: 24 beams (with 3 each of 8 di erent rebars) viz, plain round bar, ribbed bar (Fe 415), ribbed bar (Fe 500), ribbed bar (Fe 500 D), ribbed bar (Fe 550 D), PSWC-bar (pitch 30d, o set 4mm), PSWC-bar (pitch 30d, o set 5mm) and PSWC-bar (pitch 30d, o set 6mm) are cast. All beams are of 160mm x 200mm size & 1500mm in length. Beams are designed as per IS: 456:2000 and SP-16 provisions. Concrete grade is kept as M25 & same area of reinforcement steel is provided for all beams. Self Compacting Concrete(SCC) of M25 grade with OPC, Fly-ash (25 % replacement), only 10mm aggregates, river sand, potable water, and super plasticizer is used.Mix design is nalised based on EFNARC guide- lines. Various trials are carried out to nalize the mix proportion for Self Compacting Concrete (SCC). Tests adopted to verify SCC are ow test & V-funnel test. Compressive strength of cubes are evaluated for 7 and for 28 days. Finalised mix achieves 730mm ow and 11 sec to pass V-funnel test as well as compressive strength of 24 MPa at 7 days and 32.45 MPa at 28 days which is heigher than the target mean strength of 31.6 MPa. Tension tests are conducted on HYSD bars, Plain bars and PSWC-bars to compare their tensile strength and to evaluate stress v/s strain relationship. It is observed that from tension tests on PSWC-bar (with 4mm,5mm & 6mm o set) and plain round bar has same yield strength (i.e. 325.44 MPa) but lower than yield strength of HYSD bars(i.e. Fe 415 433.92 MPa, Fe 500 520.70 MPa, Fe 500 D 529.73 MPa & Fe 550 D 576.79 MPa). It has been found from tension tests that PSWC-bar gives same yield strength as compared to that of the plain bar. The HYSD bars are of higher grade as compared to that of steel. Vertical Load on the beams is applied at speci c load intervals of 10kN. Corresponding to every load, displacement and lateral strain at di erent six positions on front as well as back side of beams is measured. Crack width and length at every load interval are measured and compare it with allowable crack width as per ACI-318. Failure pattern of beam from propagation of rst crack up to failure is observed and presented with necessary photographs. Comparison of ultimate failure load, maximum displacement, lateral strain at di erent six positions on both sides of beams and experimental crack width at service load to allowable crack width as per ACI-318 of beams are presented for all categories of beams. These parameters are very essential to understand the behavior of the beams with di erent strengths and types of rebars. Analytical bending moment capacity of beams PR, PSWC-4mm, 5mm & 6mm is 7.21 kNm, Fe 500 & Fe 500 D is 13.01kNm, Fe 415 is 11.2kNm, Fe 550 D is 14kNm respectively. Shear capacity for all beams is 48.72 kN. Aver- age of experimental load of PR, PSWC-4mm, 5mm, 6mm, Fe 415, Fe 500, Fe 500 D and Fe 550 D are 109kN, 151kN, 154.67kN, 152kN, 168kN, 208.33kN, 219.33kN and 238.33kN respectively and correspondingly maximum de ec- tions at ultimate load are . Comperision of average Experimental ultimate load to analytical ultimate load gives increment in beams PR, PSWC-4mm, 5mm, 6mm, Fe 415, Fe 500, Fe 500 D and Fe 550 D are 2.08, 2.91, 2.98, 2.92, 2.50, 2.62, 2.72 and 2.76 respectively. Maximum de ection of PR is 2.99mm at ultimate load of 110kN and compare it with PSWC-4mm, 5mm, 6mm, Fe 415, Fe 500, Fe 500 D and Fe 550 D relative maximum de ections at same load of 110kN are 3.40mm, 3.45mm, 2.93mm, 3.59mm, 2.83mm, 2.88mm and 2.35mm respectively. With compare to Fe 415, maximum de ection of 5.16mm, 4.85mm and 4.14mm for Fe 500, Fe 500 D and Fe 550 D respectively. with compare to PSWC-4mm,5mm and 6mm, maximum de ection of 5.08mm, 4.32mm, 4.13mm and 3.41mm for Fe 415, Fe 500, Fe 500 D and Fe 550 D respectively. At service load of analytical allowable crack width calculated by means of co- dal provisons of ACI-318 for beams PR, PSWC-4mm, PSWC-5mm, PSWC- 6mm, Fe 415, Fe 500, Fe 500 D and Fe 550 D are 0.35, 0.35, 0.35, 0.35, 0.46, 0.56, 0.56 and 0.62 respectively. As per experimental crack width observed at service load for all catagories of beam specimen does not exceed than 0.2mm, so all beam specimens are suitable to crack width criteria given as per ACI-318. Finally the performance of PSWC-bars are compared to the performance of plain round bars and HYSD bars, for exural capacity, de ection character- istics, load v/s strain de ection relationship and crack width criteria.