Design and integrity assessment of high strength tubular structures for extreme loading conditions (Hitubes) : final report

High-strength steel (HSS) characterized by a yield strength ranging between 500 MPaand 700 MPa has been available for many years. However, its use in onshore engineering is quite restricted. Reasons were threefold: (i) Eurocodes covered steels with a yield strength up to 460 MPa; (ii) higher costs than regular steel; (iii) lack of conceptual design with HSS. Nonetheless, very recently, there has been a growing trend for the use of HSS in tubular structures due to Eurocode 3 Part 1-12 (2006), which extended its scope to steel grades up to S690/S700MC. In this context, the Hitubes project intended to develop performance-based designs and assessment procedures to make full use of HSS tubes up to S700MC for structures subject also to extreme repeated loads; in fact, Eurocode 3 Part 1-12 imposes many limitations at the material, structural and design levels. The ambitious targets are to increase the performance of tubular structures and reduce weight, construction and operating costs. The project covered the period 1 July 2008 to 31 December 2011, and the main research work focused on several aspects listed herein: literature survey; selection of finite element-based and identification dynamic analysis codes; selection of realistic case studies and FE analysis for the evaluation of actions and stresses; structural identification and health monitoring of a cable-stay and arch footbridges; test planning and execution, including welding procedure specifications; simulations of welded and bolted connections under monotonic, low-cycle and high-cycle fatigue loadings; simulation of case studies and reliability analysis for quantification of realistic performance scenarios; and SWOT analysis and monitoring of project activities.