Moment–rotation behaviour of non-bolted planar joints for segmental tunnels

Segmental tunnels cannot be considered as continuous rings due to the existence of joints. The mechanical behaviour of the segment joints is defined by the axial load in the joint. However, this load is not constant throughout the analysis, so it is necessary to make a series of iterations. A practical moment–rotation equation to represent the mechanical behaviour of typical planar joints without steel bolts is proposed. The advantage of the constitutive equation proposed in this paper is that the need for iteration is taken away because the eccentricity of the axial load remains constant during the loading process. This equation depends on the geometry of the joint, the elastic properties of the concrete and the eccentricity of the axial load in the joint. The equation was validated by means of (lab-based) experimental research on planar joints and was used in numerical models of single rings based on the finite-element method. It was concluded that this equation represents the mechanical behaviour of this type of joints correctly and, therefore, can be used to analyse single rings for segmental tunnels, reducing the computational effort spent in three-dimensional models.