Blast Modeling of Steel Frames with Simple Connections

Abstract

This paper is concerned with the problem that structural joints in whole-frame models cannot, at present, be replicated in sufficiently minute detail to realistically represent their behavior. It is well recognized that the structural joints represent the weakest link in building frames; therefore, frame models are potentially inaccurate in a critical area. The impact of this research is in the development of an accurate frame modeling approach that achieves a realistic treatment of joint response without significantly increasing the computational requirements. The method utilizes simplified connection models using rate-dependent nonlinear springs which, when assembled, allow a realistic representation of the connection behavior. The method is found to be capable of modeling strain-rate dependent material property effects with a high degree of accuracy and coping adequately with the force and rotation combinations which develop during blast response. Increased rotation rate, which occurs as a response to blast loading, is shown to modify the rotational stiffness in joints which can in turn lead to increased dynamic shear forces. Structural models which oversimplify joint stiffness and which ignore strain-rate effects are shown to lead to potentially unsafe solutions.