Ultimate strength in diagonal splitting of reinforced concrete thin wall panels

Abstract

Research carried out on reinforced concrete beams and especially on deep beams show that inclined cracking due to shear does not terminate the work capacity of a beam if a sufficient amount of the main tensile reinforcement is being well anchored beyond the support even if there is not much web reinforcement. Beams, even with inclined cracks, may be able to withstand further loading until they reach the diagonal splitting strength limit due to what often has been called arch behaviour.The authors have now attempted, on the basis of their own recent and previous research work, to present a simple formula which allows the estimation of the necessary web reinforcement and strength after diagonal splitting has occurred. The amount of web reinforcement required for the above ultimate condition is, in most cases, less than that required according to the traditional shear theory and present requirements for deep beams, as specified in ACI-318-71, Section 11.9. There are also cases where more web reinforcement is required than specified by present ACI practice; these are listed in conclusions. This would imply that there is a necessity for some revision of ACI-318-71, in order to eliminate any possible cases of dangerous under-reinforcement of deep beams in the vicinity of supports.