This paper aims to investigate the shear failure mechanisms in beams exclusively reinforced with longitudinal glass fiber reinforced polymer bars and to propose a design-based approach to predict the shear capacity of this type of beams. An experimental program composed of seven T cross section shaped concrete beams was executed to analyze the influence of the flexural reinforcement configuration on the shear capacity and deformability of the beams. Three values of the flexural reinforcement ratio (ρ l ), 1%, 1.4%, and 1.80% were adopted. Digital image correlation technique was used to better capture and analyze the cracking process up to the formation of the shear failure crack. Test results indicated that the shear capacity was not dependent of ρ l up to a limit of around 1.4%, but a tendency of the shear capacity to increase with ρ l was registered above this limit due to a more pronounced favorable contribution of aggregate interlock and dowel effect. K E Y W O R D S aggregate interlock, DIC, dowel effect, GFRP flexural reinforcement, shear capacity, shear failure, T-shaped RC beams 1 | INTRODUCTIONGenerally, the shear resistance of reinforced concrete (RC) beams or slabs is determined as a sum of the shear resistance attributed to the concrete V Rd,c and the shear resistance provided by the shear reinforcement V Rd,s . According to Eurocode 2 1 in regions of a member where V Ed ≤ V Rd,c no calculated shear reinforcement is necessary, where V Ed is the design shear force in the considered section, resulting from external loadings and prestressing force. In regions where V Ed > V Rd,c , sufficient shear reinforcement should be provided in order to satisfy the condition V Ed ≤ V Rd = V Rd,s , which means that the concrete contribution for the shear resistance of the member is not considered.Many structures constructed in 1960s have RC slabs without shear reinforcement. Since significant part of these slabs are still being used without any damage, a reasonable question that can be erased is about the reliability of actual existing codes on the prediction of the shear capacity of RC members without transverse reinforcement.On the other hand, intense research was carried out on RC members without shear reinforcement, by investigating the influence of several parameters on the shear capacity of this type of members (e.g., size effect, concrete strength, shear span-to-depth ratio, flexural reinforcement ratio). [2][3][4][5] Despite the strong research effort on the shear-transfer mechanisms in RC beams without stirrups, 3,4 this issue still raises many doubts and controversial opinions, due to the difficulties of isolating each mechanism and capture its influence on the shear capacity of an RC member, as well as the large scatter of results, even in members of same concrete strength and longitudinal reinforcement ratio.The shear capacity of RC beams without stirrups is governed by the following main shear-transfer mechanisms: aggregate interlock effect (V a ), 4 dowel action of the
