Analysis On The Bolts Connecting Tunnel Segments To Ring Beams Of Metro Station Based On The Bond-anchorage Behavior

The longitudinal bolts connecting tunnel segments to ring beams of metro stations are different from the hand hole bolts between the tunnel segments.One side of the bolt is embedded in the ring beam concrete,and there is a bond-slip effect between bolts and concrete.The anchor plate is welded at the end of the bolt,and the ring beam has a local compression area.This may affect the longitudinal stiffness,failure mode,stress distribution,and damage development of the connecting section.According to the constitutive model of bond-slip between concrete and steel,the highprecision finite element program function is utilized to investigate the concrete nonlinear behavior and cracking mechanism,and the model describing the behavior of the bond-slip mechanism is built up to measure the influence of the slip displacement on the width of ring gap.The model simulates the bond-slip between concrete and bolts by implanting interface elements at the interface.In two cases of non-anchorage plate and anchor plate,aiming at three different types of connection bolts,we simulate the bond-slip behaviors of bolts in the ring beam concrete and the width increasing of the gap between ring beam and segment.Through the quantitative analysis of the distribution of bond stress and bolt stress along the embedded bolt,the influence mechanism of bond-slip on the development of ring joint opening in the connection section is revealed.On this basis,compared with the spring model and beam model,the stiffness coefficients considering bond-slip are obtained.Finally,two variables of anchorage length and bolt diameter are introduced to further study the influence on the mechanical behavior of the connection section.The analysis shows that the bond-slip behaviors are non-negligible for measuring the connection between tunnel segments and the ring beam.For the relevant models in this paper,(1)the beam model overestimates the longitudinal stiffness,and the spring model underestimates the stiffness;(2)When the bolt yields,the contribution of bond-slip to the gap width accounts for 22% ～30%;(3)When the bolt yields,67%～87% of the longitudinal load is borne by the bond,and the anchorage plate only bears 13%～33%;(4)When the anchorage length is insufficient,the influence of anchorage length on slip ratio and longitudinal stiffness is not more than 25 %.When the anchorage length is sufficient,it has little effect on the slip ratio and longitudinal stiffness.