The design of segments is still one of biggest problems in the design of metro which are required to be solved. For building calculating model of segments
the effects of joint and ground reaction on the structure are considered mainly. We improve simplification of joint in the calculating model of segments
and deduce the formulae for solving inner forces and displacement problems in the improved model with routine method. Taking Beijing Metro Line No.10 for example
the routine method model is analyzed and compared with its improved model; and the results of numerical solution method are analyzed by comprehensiveness and verification. The study results show that the formulae derived are reliable
which are significant to the design and construction of tunnel segments in theory and practice.