Performance testing of roof beam–column connections for precast N-system

The precast N-system based on embedded-pin connections is used widely for constructing large precast industrial halls in south-eastern Europe and further afield, including areas of high seismicity. To assess realistically the seismic performances, safety margins and limitations of the connections, experimental investigations are essential. Experimental results from laboratory tests on a large-scale prototype model of the original roof beam–column connection show its actual bearing capacity, damage propagation pattern and specific failure mode. The experimental study was then extended to a prototype model of an upgraded roof beam–column connection. For better safety, the connection was upgraded with improved concrete confinement and stronger steel connecting pins. The experimental results show clearly that the implemented method for upgrading the pin-based connection provided very limited upgrading effects. To obtain much better and more reliable safety upgrading, a new innovative and effective upgrading method had to be developed. The capability of the implemented refined nonlinear three-dimensional micro-modelling concept to simulate realistically the complex nonlinear response of the tested original and upgraded roof beam–column connections was demonstrated by an extensive analytical simulation study.