FAtigue STrength of COLD-formed structural steel details

FASTCOLD is a 42-month long research project funded by Research Fund for Coal and Steel (RFCS) of the European Commission.

The project started on July 2017 and has a total budget of 2.873.935 € and an EC financial contribution 1.724.361 €.

The European Logistic industry is a sophisticated, strongly growing, important sector for the competiveness of the European market.  The size and features of warehouses and rack structures are increasing continuously to fulfil the customers´ demands. Rack structures optimized using cold-formed steel sections are the most flexible, economic and sustainable ones. On the other hand, management systems for storage and retrieval operations as well as storage and retrieval (S/R) machines are developed further to minimize the time of sheltering storage goods and the transport time in the warehouse. The S/R-machines run faster and carry higher loads in a 7/24 hour economy. Thus, the requirements for modern warehouses have substantially changed. The loading conditions on steel rack structures are no more only quasi-static, but dynamic due to the high amount of load cycles and dynamic loads caused by the S/R-machines. Repeated dynamic loads may cause fatigue failure of steel constructions. In the recent past, lots of fatigue cracks were detected  and/or fatigue failure of rack structures occurred. The logistic and racking industries have to deal with the problem of steel racks prone to fatigue. But design rules for a reliable fatigue assessment of cold-formed steel sections and details are completely missing on a European level. In fact, EN 1993-1-3 [1] is applicable for cold-formed thin-walled sections in general, but only covers the design under static loads; fatigue design is not included in EN 1993-1-3 [1] or commentaries and related design manuals (e.g [4]).  EN 1993-1-9 [3], the relevant part of Eurocode-3 for fatigue design of thick-walled, hot-rolled steel details, is not covering the fatigue design and classification of cold-formed thin-walled details. This turns out to be a major problem for the European racking industry. Important market shares of the European racking and logistic sector are at risk.

The project aims at developing fatigue design rules for cold-formed steel members and their connections,  with specific focus to applications for the logistic industry (i.e. racking systems) and at generating a classification of cold-formed structural steel details according to their fatigue strength, similar to those given in EN 1993-1-9 (for thick-walled, hot-rolled steel details), which are urgently needed for the safe design of rack structures for present and future demands.

Some of the details considered in FASTCOLD are of general use in steel structures made of cold formed members. Some other details are specific for applications of racking systems in logistic warehouses, which represent the most relevant industrial application of cold formed steel details under fatigue loading.  Other, two cases of great industrial interest where cold-formed sections are subjected to fatigue loading are transmission towers (for electricity or telecommunications) and, in the automotive industry, the fabrication of bodies of cars, buses and railway carriages (produced in cold formed steel sections).

For this reason, FASTCOLD, although aimed at solving a relevant problem of specific industrial sector of logistic, has an intrinsic wider perspective and can be considered a “pre-normative” research, because it will generate essential technical knowledge of general validity on the topic of  “Fatigue Design of Cold-Formed Structural Steel Details”  by assessing the possibility to extend the validity of the EC3-1-9 fatigue design approach to cold-formed structural steel details and by generating a classification of cold-formed structural steel details according to their fatigue strength ready  to be implemented in the relevant parts of Eurocodes.