An overview of enhancements to provisions for bond in the draft fib Model Code 2020

fib Task Groups TG 4.5 (2000-2013) and TG 2.5 (2014 to date) are responsible for major revisions to fib Model Code provisions for bond related aspects of design and detailing of structural concrete. The Authors have served as either Convenor or Technical Secretary of these task groups since 2000. The paper describes enhancements to technical content and changes in the format of (draft) Chapter 20 of Model Code 2020. The revisions and additions to technical content include: - Reformatting to determine design lap and anchorage lengths directly, removing bond strength from calculation. - Provisions for laps and anchorages in areas of high stress - Safety calibration for new design and for assessment - The influence of casting position. - Headed reinforcement - Post-installed reinforcement - Transfer lengths of pre-tensioned strand - Issues related to repair and strengthening - Consequences of deterioration, including fire and corrosion - Extensions to provisions for local bond-slip modelling - Standard method of test for bond Adjustments in the format of provisions include: - Restructuring to place ‘application rules’ ahead of more detailed models for behaviour. Introduction of Level 1 and Level 2 approximation - Introduction of a new section on Assessment of existing construction, including older types of reinforcing materials.