Bending Behavior of Bell and Spigot Joints of Segmental Precast Utility Tunnel
Bending stiffness is a critical mechanical parameter for characterizing the bending performance of joints.Mechanical bending performance tests of equal-sized bell and spigot joints were conducted to investigate the variation trends of joint strain,deflection,opening height,bottom opening,and rotation angle under bending moments and the failure characteristics of joints,and to calculate the bending stiffness of the joints,to provide a theoretical reference for the bending design of bell and spigot joints in precast utility tunnels.A mechanical analytical model for the bell and spigot joints of a precast utility tunnel was established,and analytical formulas for the bending stiffness of the joint were derived for theoretical calculations.A numerical model of the bending stiffness of the bell and spigot joints was established using the finite-element software,ABAQUS.The variations in the joint opening distance,opening height,and rotation angle with the bending moment were compared and analyzed to verify the accuracy of the mechanical analytical model of the joint.The results show that the variations in the joint opening height,joint rotation angle,and bottom opening distance with the bending moment calculated using the analytical formula for bending stiffness and the finite-element numerical model are similar to those of laboratory tests.Moreover,the results of the three methods are in good agreement,verifying the accuracy of the joint mechanical analytical model.The bending deformation of the bell and spigot joint of the precast utility tunnel can be divided into three stages:full-section compression,elastic,and ultimate bearing.The yield bending moment of the joint is approximately 83％of the ultimate bending moment,and the joint yield opening distance and rotation angle are approximately 1/3 of that of the ultimate state.The bending stiffness values in the elastic and ultimate bearing stages are 40 000 and 5 461 kN·m·rad-1,respectively.When subjected to bending moments,the top outer side of the bell and spigot joint and the bottom of the bell end are cracked and damaged under compression,whereas the top corner of the spigot end undergoes concrete spalling,resulting in joint failure.The results provide a scientific basis for the safety evaluation and design of the bending performance of bells and spigot joints in precast utility tunnels.
tunnel engineeringprecast utility tunnelbending testbell and spigot jointbending stiffnesscalculation model
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