Abstract
In this paper, the authors reexamined the evaluation method, proposed previously by the authors, on the effect of opening of joints on soil constraint around a tunnel, first. Then, the authors reevaluated joint stiffness of actual tunnels and the influence of the use of such stiffness on earthquake response results of tunnels. Next, earthquake response analyses were conducted in consideration of stiffness degradation of tunnel lining due to cracking, and results of the earthquake response analyses were evaluated. Finally, based on such examinations, the authors summarized a new earthquake resistant design method, taking consideration of the features as follows. Reinforcing bars in the longitudinal direction should be arranged so that the tensile yield strength of reinforcing bars may become greater than the ensile strength of concrete lining, without over evaluating joint behavior, in the area where earthquake ground strain is not large, In the area where ground strain is large, on the contrary, average strain of tunnel lining should be reduced, by arranging joints in consideration of soil constraint around a tunnel.
