Experimental study on shear performance of steel shell-concrete composite structure in immersed tunnel

Abstract

Based on local arrangement details in the top slab of Shenzhen–Zhongshan Link immersed tunnel, steel shell-concrete (SSC) composite specimens with 1:2.5 scale were prepared and tested under shear, to investigate the effects of transverse T-shape stiffeners on shear capacities, crack development, and relative slip. Finite element models were also built and verified by the experimental results. For the specimen without transverse stiffeners, the failure at the steel plate-concrete interface occurred firstly, and then top and bottom steel plates were separated from the compression concrete core. While for the specimen with transverse T-shape stiffeners, the concrete cracks developed diagonally from the flange edge of T stiffeners near the bottom steel plate in sequence, and the corresponding tension field in the steel web enlarged gradually until full web yielding, as the shear force increased. Compared to specimens without transverse stiffeners, when transverse T stiffeners were placed in SSC composite specimens, the shear force at initial cracking was much smaller, but the yielding and ultimate shear capacities were increased by 12.2% and 14.6%, respectively. Although earlier cracking induced, the transverse T stiffeners were beneficial to improve shear capacities of SSC composite structures. The maximum relative slip at steel plate-concrete interface of specimens with and without transverse T stiffeners were 0.28 mm and 0.62 mm before the structure reaching the yielding stage, respectively, indicating that transverse T stiffeners could reduce the relative slip and separation between steel plates and concrete core, ensuring the effective composite action of steel plates and filled concrete. T stiffeners could improve the compressive behavior of concrete. With transverse T stiffeners placed in SSC composite structure, and the shear force could be resisted by both the diagonal compressive core in concrete and the arch system formed with the T stiffeners.