Structural Behavior And Design Method Of Steel/Concrete Composite Ice Walls for Arctic Offshore Structures

ABSTRACT In order to develop an optimum steel/concrete composite ice wall for the arctic offshore structures, structural behavior of the steel/concrete composite sandwich beams with double skin plates was studied by test. From the test, the steel/concrete composite structures with appropriate shear reinforcement were confirmed to exhibit a good structural performance, i.e., large load carrying capacity and high ductility required for the arctic offshore structures. Based on the test results and analysis, a simplified design method of the steel/concrete composite sandwich structures was developed. I. INTRODUCTION Steel/Concrete Composite Structures The arctic offshore structures should withstand huge ice loads. Although the magnitude of the ice loads has been differently evaluated depending on the locations and the investigators, the intensity may reportedly be as large as 10 MPa. Thus, the ice loading on the arctic structures is undoubtedly very large and severe. When the all-steel structure should be installed against those severe loads, the steel plate would be uneconomically thick and considerable number of stiffeners should be provided for the structure. On the other hand, when the all-concrete structure would be adopted, impractically heavy reinforcement should be provided and the weight of the structure becomes relatively heavy, leaving the structure not necessarily suitable for towing or relocation. Taking note of these backgrounds, the steel/concrete composite ice wall structures are proposed as one of the best structural solutions against ice loading. The sandwich structure, having the double skin plates filled with concrete, is one of the steel/concrete composite structures, and it has a potential to enhance the constructability which may lead to the reduction of the construction period and cost. The specific application of the steel/concrete sandwich structure to the ice walls is a relatively new concept, and the actual behavior of this structural type is not necessarily well understood. Though some studies have reportedly been conducted on the appraisal of the strength performance of several specific sandwich structures (Refs. 1–3), a rational design method for the actual structural members of this type still needs to be established. Objective and Scope The objective of the test was to understand the basic structural behavior of the steel/concrete composite sandwich structure with double skin plates, and to provide a design method of such a structural member. The experimental study was conducted using one third scaled model beam specimens of the conceived actual steel/concrete sandwich structures. In the experiment, failure mode, deformation characteristics and ultimate strength of the specimens were investigated. Variables in the model tests were shear span-to-depth ratio, steel index, and type and amount of shear reinforcement, etc. Based on the test results, an effort was made to find an appropriate estimation method of the load carrying capacity of the steel/concrete composite sandwich structure. Following this effort, a simplified strength evaluation method has been proposed, which enables the optimum design of the steel/concrete composite ice wall structure.