Experimental and analytical study of Friction Connection for seismic retrofit with Cross-Laminated Timber (CLT) panels

Within the European project e-SAFE (Energy and Seismic AFfordable rEnovation solutions), this paper presents the experimental tests and modeling attempts for a class of Asymmetric Friction Connections (AFCs) tested in the laboratories of the Norwegian University of Life Sciences. The AFCs are part of the seismic retrofitting solution, called e-CLT, based on installing Cross-Laminated Timber (CLT) panels in reinforced concrete structures using friction connections. The authors carried out experimental tests on AFCs fixed with screws to a CLT panel to observe the contribution of timber to the total dissipation performance. The investigation is based on 20 cyclic test data with two different setups. The main one includes a CLT panel and screw connection, while the second one isolates the friction behaviour to evaluate the influence of the screw connection. A modified LuGre hysteresis model for friction is developed to simulate the experimental cyclic response of the tested specimen. The model possesses a direct physical meaning, and it explicitly depends on the slip force and the pre-slip stiffness. The optimized model is used to assess the performance of the AFC by varying the pre-slip stiffness and the slip force.