Design and integrity assessment of high strength tubular structures for extreme loading conditions

High Strength Steel (HSS) characterized by yield strength ranging between 500MPa to 700MPa has been available for many years. However, its use in onshore engineering is quite restrictive. Reasons were threefold: i) Eurocodes covered steels with yield strength up to 460MPa; 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 thanks to Eurocode 3 Part 1-12 (2006), that extended its scope to steel grades up to S690/S700MC. Along this line, 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 level. The ambitious targets are to increase the performance of tubular structures, reduce weights, construction and operating costs.
The project covered the period 01/07/2008-31/12/2011, and main research work focussed 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; tests 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; SWOT analysis and monitoring of project activities.