Effect of Rebar Cover and Development Length on Bond and Slip in High Strength Concrete

K. Ahmed, Z. A. Siddiqi, M. Ashraf, A. Ghaffar

Abstract


Composite behavior of reinforced concrete requires adequate bond between concrete and steel reinforcement that can transfer stresses between them. The bond strength is influenced by cover to the reinforcement and development length. Experimental investigation was carried out and twisted steel bars conforming to BS 4461 were used in high strength concrete to study bond strength characteristics. The post peak bond behavior was studied by using displacement controlled universal testing machine. The results of this experimentation confirmed that by increasing the cover/bar diameter ratio, bond strength increased and slip decreased for both small and large diameter twisted steel bars. This increased confinement reduced the uneven bond stress distribution along the development length. Stress concentration on the front key (concrete between two ribs) was reduced due to its continuity along the twisted steel bar. Hence it offered maximum possible resistance to bond failure and the bond strength increased. Similarly by increasing the development length, bond strength and corresponding slip both increased. Another fact visible from all figures and observed in all samples, is that as the first concrete key failed there was a sudden drop in bond strength due to the formation of longitudinal splitting cracks. These cracks are visible from the surface of the cylinder. Once a key is failed, failure propagated immediately.

Full Text:

PDF

References


Al-Negheimish A. I., Al-Zaid R. Z.; Journal of Cement & Concrete Composites, 26(2004) 735- 742.

Ahmed K., Siddiqui Z. A., Yousaf M.; Pak. J. Engg. & Appl. Sci., Vol.1, (2007), pp31- 40.

Weisse D., Ma J.; Leipzig Annual Civil Engineering Report, Germany, 8(2003), 175- 184.

Ma J., Schneider H.; Leipzig Annual Civil Engineering Report, Germany, 7(2002), 25-31.

Rizwan S. A.; High performance mortars and concrete using secondary raw materials, 1st ed, ISBN: 978-969-546-014-6, A-One, (2006), 17-21.

Kankam C. K.; Journal of Structural Engineering ASCE, 123(1997) 97-85.

Tue N V, Krumbach R.; Leipzig Annual Civil Engineering Report Germany, Vol. 2, (1997), pp 171-189.

Mo Y. L., Chan J.; Journal of Materials in Civil Engineering, l8/4(1996) 208-211.

Harajli M. H.; Journal of Materials in Civil Engineering, 16/4(2004) 365-374.

Newman J., Choo B. S.; Advanced concrete technology, 1st ed, ISBN 0750651040, ELSEVIER, Butterworth Heinmann, (2004) 3/7.

Tastani S. P., Pantazopoulou S. J.; Bond in concrete-from research to standards, Budapest, Hungary, (2002), 1-8.

Tue N. V., Krumbach R.; Leipzig Annual Civil Engineering Report, Germany, No3, (1998), 73- 84.

Abrishami H., Mitchell D.; Journal of Structural Engineering ASCE, 122/3(1996) 255-261.

ACI; Fracture mechanics of concrete: concepts, models and determination of material properties, ACI Committee 446.1 R-91, (Reapproved 1999).

Broek D.; Elementary engineering fracture mechanics, 1st ed, ISBN: 90 286 0304 2, Noordhoff International Publishing Lyden, (1974), 11-14.

Ichinose T., Kanayama Y., Inoue Y., Bolander J. E.; Journal of Construction and Building Materials, 18(2004) 549-558.

Weisse D., Holschemacher K.; Leipzig Annual Civil Engineering Report, Germany, No8, (2003), 251-261.

Tepfer R.; Journal Chalmer University of Technology, (1973).






Copyright (c) 2016 Kafeel Ahmad

Powered By KICS