13.06: Calibration of Eurocode design models of thin‐walled cylinder under bending with full scale tests

Abstract

ABSTRACTDesign formulas for thin‐walled cylinders in bending show remarkable differences in various codes, including versions of the Eurocodes. Thin‐walled, high grade steel cylinders are used in piles, e.g. in combined walls for quay wall construction or in large mono‐piles for mooring structures or offshore foundations. These piles experience a dominant loading in bending, and may be designed with Eurocode formulas for shell buckling of prismatic cylinders.In recent years, a relatively large number of new results of full scale experiments has become available. These results can be combined with test results from the literature and can be used for calibration of the design model formulas for thin‐walled tubes, in particular in the range that has a high susceptibility to elastic or plastic local buckling. The diameter range of the tests is 400 to 900 mm. The d/t ratios range from 40 to 110 and the steel grades from S235 to S460.New capacity‐based formulas for Reference Resistance Design (RRD) of cylinders in bending have been developed from extensive GMNIA calculations (geometrically and materially nonlinear analyses with imperfections included) that included many variations of the relevant parameters and buckling pre‐conditions. A calibration against the tests forms a potentially valuable confirmation of those design rules. The methodology of the calibration is based on statistical procedures that prove sufficient reliability according to the Eurocode requirements.Similar to other calibration exercises, it appears that the difference between the nominal and real material strength is, amongst other aspects, an important input parameter for the calibration result.The evaluation performed here shows that the published Eurocode EN 1993–1–6 2007 strength‐based formulas produce conservative results and that the new RRD amendment which produces less‐conservative design values can still be safe.