Lightweight steel-concrete-steel sandwich composite shell subject to punching shear

The development of Arctic oil and gas fields requires high strength structures that can resist critical loads in extreme environment. A novel conical caisson structure constructed by lightweight steel-concrete-steel (SCS) sandwich shell is proposed for withstanding ice pressure imposed thereon by impinging sheet ice in Arctic region. This paper mainly investigates the ultimate strength behaviour of SCS sandwich shell experimentally and analytically. Two pilot quasi-static tests on the lightweight SCS sandwich composite shells subject to patch loading are carried out. The failure mode of composite shell is punching shear. Tests show that the punching shear resistance depends on the control perimeter of punched concrete frustum and shear connectors. The membrane action of the outer steel plates provides post-hardening strength. On the basis of the experimental failure mechanism, an analytical model is developed to explain the force transfer mechanism and predict the punching shear resistance of SCS sandwich composite shell. The verification of the model shows that the predictions are in good agreement with the test results. It is also shown that the SCS sandwich shell, in accord with the ISO ice load design, is capable of resisting the localised contact and punching loads.