SEISMIC RESPONSE AND STIFFNESS OF TUNNELS IN THE LONGITUDINAL DRECTION IN CONSIDERATION OF THE EFFECT OF JOINTS AND CRACKS

Abstract

 In the seismic design of urban tunnels in the longitudinal direction, a concept, in which axial strain can be reduced by longituginal joints, is generally adopted. However, spring constants for axial joints, determined by back calculation using the numerical results obtained from computer simulations or earthquake observations, is much greater than that calculated simply from a structural model of uurban tunnels in the longitudinal direction. In this paper, therefore, the authors propose a new design concept, in which cracks come up in tunnel lining and the tensile stiffness of tunnel lining is reduced. Then, this paper proposes a method to control a stress-strain relationship of reinforced concrete lining based on a response displacement method, using the amount of reinforced steel as a parameter.