Abstract: The concepts of ring stiffness, pipe stiffness and nominal stiffness of the glass fiber reinforced plastics mortar pipe are analyzed. Ring stiffness is a kind of ability of pipe ring under the action of the external load resistance to deformation. Pipe stiffness and ring stiffness is not the same concept, and nominal stiffness is the initial specific ring stiffness level. The basic method of design and test of ring stiffness is analyzed, and according to the design requirements of nominal stiffness required in practical engineering are analyzed from two aspects of deflection and buckling. The basic principles and methods of determine nominal stiffness and the relationship between ring stiffness and embedment conditions are obtained. It has reference significance to correctly understand ring stiffness of glass fiber reinforced plastics mortar pipe and ring stiffness design, test and selection.

Key words: glass fiber reinforced plastics mortar pipe, ring stiffness, pipe stiffness, nominal stiffness, composite soil constrained modulus