The infiltration of gas and water into the tunnel may cause serious safety problems and the control of leakage should not be underestimated in the design phase. Simulating the mechanical behaviour of longitudinal joints in segmented tunnel linings in a reliable manner serves not only from the viewpoint of structural design but also for the evaluation of the sealant capacity of the lining. Joints may be subjected both to monotonic or cyclic loading (e.g. earthquakes or groundwater oscillations). Excessive relative rotations may produce plastic deformations (i.e. damage of the joint) and reduction of the sealant capacity. Most of the current mechanical models are able to capture the monotonic behaviour of joints whereas the cyclic behaviour has not been investigated to the same extent. In this paper, a cyclic model for longitudinal joints that is capable to simulate the cyclic behavior of asymmetric, bolted cross-sections is proposed. The distinctive feature of the proposed model is the variation of the rotational stiffness of the joint that depends on: (i) the sign of bending moment, (ii) level of axial load, and (iii) damage accumulation or failure. The reliability of the formulation is evaluated through comparison with experimental data.
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