Non-linear modelling approach and seismic investigation of bolt-connected precast concrete frames

Bolt-connected precast concrete systems have been widely used in the construction field in the last century, and currently constitute a large part of the industrial-building application market. When comparing complex precast joints, this type of connection exhibits high efficiency and convenience. The seismic assessment of existing industrial buildings and preliminary design of new ones are critical issues currently being researched. In this paper, a non-linear modelling approach for bolt-connected precast concrete frames is proposed. The resist mechanisms of simple bolt-connected joints against shear forces and moments are precisely described. The mechanical models of different types of connections are derived from the tensile properties of the anchor bolt, shear behaviour of the shear bolt and flexural behaviour of angle steel. This modelling method facilitates rapid analysis for the retrofitting of existing bolt-connected precast concrete-frame buildings and seismic design of new ones. Based on a shaking table test of a bolt-connected precast concrete frame, a non-linear numerical model is constructed using the proposed method and its validity is verified by comparing the test results. For further study, the seismic performance and characteristics of this bolt-connected frame are analysed, covering the stress and strain responses of material fibres as well as the connection behaviours. The analysis results show that the precast connections and interior columns are the most dangerous elements, under earthquakes. The structural members in upper storeys maintain safer stress and strain states than those in the first storey. These simple bolt-connected joints are susceptible to seismic actions and are prone to lose their moment-resisting capacity under moderate earthquakes. Thus, this system is observed to behave poorly under moderate and severe earthquakes, and should be carefully concerned.