Square and rectangular hollow sections are generally produced either by hot-rolling or coldforming. Cross-sections of nominally similar geometries, but from the two different production routes may vary significantly in terms of their general material properties, geometric imperfections, residual stresses, corner geometry and material response and general structural behaviour and load-carrying capacity. In this paper, an experimental programme comprising tensile coupon tests on flat and corner material, measurements of geometric imperfections and residual stresses, stub column tests and simple and continuous beam tests is described. The results of the tests have been combined with other available test data on square and rectangular hollow sections and analysed. Enhancements in yield and ultimate strengths, beyond those quoted in the respective mill certificates, were observed in the corner regions of the cold-formed sections -these are caused by cold-working of the material during production, and predictive models have been proposed. Initial geometric imperfections were generally low in both the hot-rolled and cold-formed sections, with larger imperfections emerging towards the ends of the cold-formed members -these were attributed largely to the release of through thickness residual stresses, which were themselves quantified. The results of the stub column and simple bending tests were used to assess the current slenderness limits given in Eurocode 3, including the possible dependency on Gardner, L., Saari, N. and Wang, F. (2010) Comparative experimental study of hot-rolled and cold-formed rectangular hollow sections. Thin-Walled Structures. 48(7), 495-507. 2 production route, whilst the results of the continuous beam tests were evaluated with reference to the assumptions typically made in plastic analysis and design. Current slenderness limits, assessed on the basis of bending tests, appear appropriate, though the Class 3 slenderness limit, assessed on the basis of compression tests, seems optimistic. Of the features investigated, strain hardening characteristics of the material were identified as being primarily responsible for the differences in structural behaviour between hot-rolled and coldformed sections.

The present generation of international structural steel design codes treats material nonlinearity through simplified elastic-plastic or rigid-plastic material models. However, the actual stress–strain response of structural steel is more complex than this and features, in particular, strain hardening. Strain hardening refers to the increase in strength beyond yield because of plastic deformation. The influence of strain hardening on the behavior and design of steel structures is examined in this study through both the experimentation and the analysis of existing data, and a method to exploit the additional capacity that arises is outlined. Both determinate and indeterminate structures are considered. The proposed design method, referred to as the continuous strength method (CSM), is a deformation-based design approach employing a continuous relationship between cross-sectional slenderness and cross-sectional deformation capacity, together with a material model that allows for strain hardening. Comparisons are made between test results generated as part of the present study and collected from existing studies, and the predictions from the CSM and Eurocode 3 (EC3). For all cases considered, the CSM, through a rational exploitation of strain hardening, offers a more accurate prediction of observed physical behavior.

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Catenary Anchor Leg Moorings (CALM) buoys are offshore structures that have been used for offloading, loading and discharge purposes. In this study, dynamic analysis is carried out on the submarine hoses attached to a CALM buoy and moored by six mooring lines in a water depth of 23.0m. Two submarine hose-strings in Chinese-lantern configuration are attached underneath the buoy. Three environmental conditions are considered, representing West Africa Sea, North Sea and Gulf of Mexico (GoM), respectively. Hydrodynamic simulation using ANSYS AQWA is first conducted to determine response amplitude operators (RAOs) of the buoy. Coupled dynamic models, where both buoys and hoses are included, are developed using Orcaflex. Parametric studies are conducted to investigate the effects of hose hydrodynamic loads and flow angles on the structural behaviour of the hoses, including bending moments, effective tension and minimum bend radius. From the study, a guidance dynamic amplitude factor of 2.0 considering hydrodynamic loads on hose DAFhose is proposed.

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