# Experimental Study on Vertical Shear Behaviors of an Immersion Joint with Steel Shear Keys
## 6 Conclusions  
This paper presents an experiment to investigate the vertical shear behaviors of an immersion joint with steel shear keys subjected to multidirectional loads. Three different specific loading cases are  
Figure 14: Immersion joint model (units: mm). (**a**) Failure of the shear key; (**b**) broken rubber bearing; (**c**) cross-section of the fallen shear key.  
carried out, and the values of the applied loads as well as the displacements are obtained. Based on the results and analysis of the experiment, the following conclusions can be drawn:  
(1) Below the vertical shear load of 350 kN, the shear force-displacement curves can be divided into two stages. Stage 1 is mainly the compression of the rubber bearings and exhibits a non-linear development. Stage 2 is where the shear resistance provided by the steel shear keys is gradually enhanced and finally occupies the main shear capacity of the joint, which exhibits a quasi-linear development. Moreover, due to a larger compression of the GINA rubber gasket, the vertical shear stiffness of the joint increases when subjected to a larger compressive load.  
(2) As the transverse shear load is applied, friction will be generated because of the contact between the horizontal shear keys. Hence, the friction shares part of the shear force and enhances the vertical shear stiffness of the joint in the compression-bidirectional shear test.  
(3) Because the shear keys do not carry the shear force simultaneously, the ultimate shear capacity of the joint (690 kN) turns out to be smaller than the sum of the shear capacities of all the vertical steel keys (880 kN). In addition, it can be deduced that the GINA rubber gasket contributes to the shear stiffness and shear capacity of the joint.  
(4) The failure of the joint appears at the VSKA in the middle of the right sidewall. The rubber bearing fixed on this shear key is compressed until it bursts, and all the bolts are cut off. These phenomena indicate that the failure mode of the joint is a single failure of one shear key on the sidewall, which leads to a shear resistance failure of the entire joint.  
It should be noted that limitations of the experiment still exist and subsequent research works also need to be done. This paper mainly introduced the design ideas, test procedures and test results of this experiment in detail, however the corresponding numerical simulation studies and validations will be introduced in the subsequent papers. Different kinds of the GINA rubber gaskets and temperature conditions should be taken into consideration in the future studies. Moreover, parametric analysis of different geometric parameters and component positions of the immersion joint should be taken into account as well.  
Conceptualization, Y.Y. and J.L.; methodology, H.Y.; software, J.L.; validation, Y.Y., J.L. and H.Y.; investigation, J.L.; resources, Y.Y.; writing--original draft preparation, J.L.; writing--review and editing, Y.Y.; supervision, Y.Y. and H.Y.  
This research was funded by the National Key Research and Development Plan of China (2018 YFC0809602 & 2017 YFC1500703), and the National Natural Science Foundation of China (51778487 & 51678438).  
The research has been supported by the National Key Research and Development Plan of China (2018 YFC0809602 & 2017 YFC1500703), and the National Natural Science Foundation of China (51778487 & 51678438). The above supports are greatly acknowledged.  
The authors declare no conflicts of interest.