Behaviour of Beams Without Transverse Reinforcement

Abstract

To deepen the understanding of shear behaviour in beams without transverse reinforcement, the relative importance of five contributing factors to concrete shear resistance(), which are i)flexural compression zone, ii)friction at crack faces, iii)dowel action, iv)arch action and recently identified, v)residual tensile stresses across cracks, was explained physically using two analytical methods based on the truss concept. One is called Modified Compression Field Theory(MCFT) considering ii) and v) explicitly, and the other Crack Friction Truss Model(CFTM) more dominantly ii) in determining concrete resistance. To verify their effectiveness, the predictions using MCFT and CFTM were also made for twenty KAIST beam tests(=53.7Mpa), designated more likely to the development of the size effect law based on the fracture mechanics concept. Experimental findings with varying of a/d, longitudinal reinforcement ratios, and obtained from MCFT enabled additional explanations for some phenomena which were difficult to measure in tests. However, MCFT seemed somewhat conservative for beams with higher longitudinal reinforcement, while somewhat unsafe for beams with larger depths. More tests are necessary leading to firm conclusions in these areas.