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RCBCJSR - Strengthening and rehabilitation of beam-column joints of reinforced concrete frames

Title: RCBCJSR - Strengthening and rehabilitation of beam-column joints of reinforced concrete frames

Principal investigator: Paulo Providência

Research team: Miguel Ferreira

Dates start/end: 10-2016 / 03-2018


Inadequately designed reinforced concrete beam-column joints (RCBC joints) can lead to hard to predict, premature and non-ductile failure modes of moment resisting frames (MRFs). This is even more likely under seismic actions when RCBC joints have substandard detailing such as lack of transverse reinforcement in the joint core, the use of plain round bars and inadequate anchorage of the beam and column bars, typical of pre 1970 construction practice.

Among the RCBC joint models developed so far the macro-element type models seem to be the ones that better fulfil the requirements of objectivity, versatility, soundness, efficiency and robustness. On the other hand, a RCBC joint retrofitting technique that has revealed good results and actually seems to be feasible, independently of the joint typology, is the Fully Fastened Haunches (FFH). FFH consists in the introduction of haunch elements (a machined bar/plate connected to plates at both ends) connected to beam and column near to the RCBC joint using post-installed mechanical anchors.

This research project recognises addresses (i) the assessment and modelling of the static and cyclic behaviour of RCBC joints, particularly the combined effect within the joint of the forces applied at its boundary, and (ii) the development and implementation in common FEM based programs of suitable FEM models for RCBC joints properly/poor designed, possibly retrofitted using FFH.

The investigation encompasses the following steps: (i)identification of the most relevant systems of forces applied at RCBC joints periphery, (ii) quantification and modelling of the combined effect of these systems of forces on joint behaviour, (iii) quantification and modelling of FFH on RCBC joint behaviour, (iv) development of a RCBC joint model which applies as-built RCBC joints as well as to joints retrofitted with FFH, (v) implementation of the RCBC joint model in FEM based software and (vi) improvement of the available design and strengthening procedures for RCBC joints.