Proposal and experimental validation of simplified strut-and-tie models on dapped-end beams

摘要

Dapped-end beams are frequent precast concrete elements. Spalling on the top of the hanger reinforcement has been observed to be often their governing failure mode. This failure hinders the geometric definition of strut-and-tie models for design or assessment purposes. In this work, a simplified procedure for defining the geometry of strut-and-tie models considering spalling failures is proposed. The model is based on the results of a specific experimental programme consisting on twenty-eight tests on fifteen different reinforcement configurations with and without inclined reinforcement. The experimental results show that elements with high amounts of reinforcement and hanger reinforcement concentrated in one layer are more prone to spalling failures, and suggest that the geometry of strut-and-tie models is strongly influenced by the behaviour of the nodal region on top of the hanger reinforcement. The model is verified for tests with and without spalling failures, including elements from the literature, showing sound agreement between the modelling results and experimental observations.