Rigid body moment–rotation mechanism for reinforced concrete beam hinges

Structural engineers have long recognised the importance of the ductility of reinforced concrete members in design, that is the ability of the reinforced concrete member to rotate and consequently: redistribute moments; give prior warning of failure; absorb seismic, blast and impact loads; and control column drift. However, quantifying the rotational behaviour through structural mechanics has been found over a lengthy period of time to be a very complex problem so that empirical solutions have been developed which for a safe design are limited by the bounds of the test parameters from which they were derived. In this paper, a rigid body moment–rotation mechanism is postulated that is based on established shear-friction and partial-interaction research; it is shown to give reasonable correlation with test results as well as incorporating and quantifying the three major limits to rotation of concrete crushing and reinforcing bar fracture and debonding.