TY  - JOUR
AU  - Sirimontree, Sayan 
AU  - Witchayangkoon, Boonsap 
AU  - Khaosri, Nathavudh 
AU  - Teerawong, Jaruek 
PY  - 2011
TI  - Shear Strength of Reinforced Concrete Beam Strengthened by Transverse External Post-tension
JF  - American Journal of Engineering and Applied Sciences
VL  - 4
IS  - 1
DO  - 10.3844/ajeassp.2011.108.115
UR  - https://thescipub.com/abstract/ajeassp.2011.108.115
AB  - Problem statement: Shear failure of concrete beam is brittle manner without warning so
inadequate design for shear of beam and/or material deterioration lead to the possibility of sudden
failure of beam. The change of functional use and future increased load of structure lead to the need for
strengthening of concrete structure. Approach: This research focuses on behaviors under static
loading of reinforced concrete beam, with shear strengthening by transverse external prestressing
force. Post-tension high strength steel is vertically applied in shear span. Total eight beam specimens
are divided into two groups each having shear span to depth ratios 2 and 1.5. Each beam, possessing
the same reinforcing steels, is intentionally designed to be failing in shear. One of the beams from each
group is used as reference, without shear strengthening. The other three specimens from each group are
applied different amounts of external prestressing force. Results: The experimental result shows that
ultimate load carrying capacity of all shear strengthened specimens significantly improves over the
reference specimen. The higher the amount of applied strengthening force, the greater the ability to carry
ultimate loading. Failure mode shifts from brittle shear failure closer to ductile flexural failure, with
higher ductility and stiffness. External prestressing force in transverse direction of shear span of beam
enhances ultimate shear capacity by improving aggregate interlocking, preventing splitting cracks caused
by debonding of longitudinal reinforcing steels due to dowel action. Furthermore, load at first diagonal
tension cracks are increased as a result of pre-compressed prestressing force leading to the higher ultimate
load carrying capacity. Moreover, concrete in compression zone remains uncrushed at ultimate state.
Strut-and-tie model can be used to predict ultimate loading capacity of beam specimen and failure
mechanism of both specimens with or without strengthening. Conclusion: Shear strength of reinforced
concrete beams strengthened by transverse external post tension at shear span is effectively improved
over reference beam specimen. Strut and tie model can be conservatively predicted the ultimate shear
capacity of both reference and strengthened beam specimen.