Unifying strut-and-tie models at micro and macro-scale level in concrete-to-concrete connections

Abstract

Strut-and-tie model (STM) is a powerful tool to physically define the load transfer mechanism in reinforced concrete and has been widely used in reinforced concrete design for disturbed regions featuring non-flexural strain sections. In this paper, a unified concept of STM is extended to contemporary construction methods for concrete-to-concrete connections, featuring post-installed rebar (PIR) fastening technology. At micro-scale level, STM is used to describe the bond strength of rebar to adhesive and adhesive to concrete material. This is followed by discussions with an example on using STM at macro-scale level, for simply supported (shear only) members connected with PIR as starter bars. Five design proposals are put forward to effectively unifying the use of STM to arrive at actual design stress in concrete-to-concrete connection, which gives the benefit of shorter anchorage length as opposed to current design method of cast in-situ reinforced concrete. TR069 (2019) was included to better account for bond and splitting checks at the hogging moment in a fixed connection. Finally, a more sophisticated frame-node method using STM is briefly introduced.