Shear behavior of UHPC beams with small shear span to depth ratios based on MSTM

Ultra-high performance concrete (UHPC) has been gradually used in structural engineering due to its excellent mechanical performance, however, predicting the shear behavior of the UHPC beams at service load conditions is still a big challenge, especially for the beams with small shear span to depth ratio. To address this issue, this paper devotes to develop a modified strut and tie model (MSTM) to predict the shear behavior of the UHPC beams with stirrups throughout the loading process. The principle of stationary complementary energy has been introduced into the MSTM to decouple the contribution of arch action and truss action on shear forces. Based on the MSTM, the shear force resistance mechanism has been revealed, and simplified models at each load step have been developed to estimate the shear behavior of UHPC beams. 12 UHPC beams were designed and tested to validate the proposed model. The proposed model was verified to be sufficiently accurate. Moreover, it can be noted that the current design codes, including SETRA-AFGC and SIA, give overly conservative values for UHPC beams when the shear span to depth ratio is less than 2.5.