Design recommendation for steel beams subject to impact load to prevent brittle fracture

Abstract

Recent catastrophic events, involving the accidental loading of structures caused either intentionally for example aircraft crashes on structures, blast loadings, or unintentionally due to object impact, gas explosions etc, has changed our view from something connected to the stage of war to a much more domestic scene. This makes it imperative to study the response of structural elements under such accidental loading conditions in an attempt to assess structures vulnerability and characteristic performance. The study presented in this paper investigates the response of steel beams under impact loads by using the energy principles in assessing the capacity of the steel beam to absorb impact energy in deflecting before fracture ensues. In addition, the point at which the ductile material is considered to have failed was also examined, in an attempt to give safety recommendations to steel structures under impact. This study also looks at the evaluation of dynamic loads, different impact scenarios, behaviour of steel material at high strain rates (i.e. dynamic increase factor DIF) as well as influence of joint rotation on failure. The findings from this study show that the maximum strain energy beyond which the beam is considered to have failed is largely influenced by joint rotation.

Keywords: Structural behaviour, Impact scenario, High strain rate, Joint rotation and Dynamic load