Performance of cold formed steel angles under fatigue loading

摘要

Cold formed steel sections are increasingly used these days in structural applications due their inherent high strength to weight ratio. Further, the cost of transportation, erection and foundation is enormously reduced due to their light weight characteristics. Most of the codes of practice for the usage of cold formed steel sections in structural applications, deal only with static conditions of loading. Under dynamic situations, cold formed light gauge steel sections experience very low inertia forces as compared to hot rolled sections because of their low mass. Hence the thought of using cold formed steel sections under dynamic loading conditions become attractive. Even though the static behaviour of cold formed elements is well established, fatigue behaviour of these elements under fluctuating loads needs to be investigated. Angle sections are the most common steel structural elements. They are extensively used in Towers, Multi-storeyed Industrial Structures etc. The aim of this investigation is to examine the performance of cold formed steel angle members when subjected to fatigue loading. Tests have been conducted under constant amplitude sinusoidal and stepped loading on single angle specimens using servo hydraulic static-dynamic UTM. Based on the results the influence of fatigue parameters, like Maximum stress, Minimum stress, Stress range and type of loading on fatigue life is studied. An attempt has been made to study the fatigue crack growth rate using Fracture Mechanics principles. Empirical relations to estimate fatigue life and crack growth rate have been developed.