Limit state of a concrete sliding hinge connection

Abstract

The suitability of a cylindrical concrete sliding hinge connection in modern reinforced concrete structures has not been investigated yet. This type of connection is known for its large normal force capacity and a rotation limit only based on the geometry of the connection. For the case of underground constructions, large normal forces are often present at the wall-to-floor connections. Considering the risk of uneven settlements, such connections may also demand sufficient rotation capacity. This research is aimed at deriving the limit state of the connection and the surrounding concrete structure. A test program is carried out to support the research, where full scale experiments are performed at the Stevin II laboratory of the Delft University of Technology. The goal is to prove the functioning of this type of hinged connection in a system before it is implemented in practice. Different analytical contact models are investigated and implemented aiding in quantifying the performance of the connection. A finite element model is used to verify the analytical models and to obtain the stress distribution in the connection. Two different bearing types are investigated in its ability to aid the sliding in the connection: a bituminous and a PTFE-stainless steel interface. Both the PTFE-stainless steel and the bituminous interface are adequate to allow sliding with low rotational resistance. Significantly lower bending moments are obtained during testing compared to a conventional monolithic connection. From the testing project it is found that the capacity of the cylindrical hinge for the given reinforcement design is significant when loaded in the normal direction. The concave concrete element can fail in a splitting failure mode when loaded to the normal force limit. The bituminous interface shows the ability to spread contact stresses and allow for reduced cracking under large normal force loads. Large loads in shear, in combination with low levels of normal force is a point of attention to prevent shear cracks, irrespective of the type of bearing. It is found that the hinge functions fine with favourable frictional behaviour for large shear forces indicating the ability to cope with these forces when a sufficient reinforcement design is implemented.