Dynamic Analysis and Seismic Design of Mine Headframes

2019

Mickael Hardy, WSP in Canada

Background The structural design of mine headframes is often challenging due to the significant differences in the geometry, rigidity, and behaviour of these structures compared to conventional buildings. The differences are related to the main purpose of these structures, which is not human occupancy, but rather the support of hoisting equipment. Currently, the structural design of mine headframes is carried out according to the same standards used for conventional buildings, with input from various guidelines, handbooks, and other references. The designers must adapt these standards to the headframe design, which can result in the structures being either over-designed or under-designed. In the latest update of CSA S16 “Design of Steel Structures”, Annex M (informative) has been added to provide designers guidelines for the seismic design of industrial structures. Objective The main objective of this paper is to study the dynamic behaviour of headframe structures in comparison with conventional buildings, which are the base case for the definition of seismic loads and evaluate the impact of various design philosophies. Methodology First, the dynamic behaviour of headframes is studied using modal and spectral analysis, and the results are compared to the equivalent static analysis proposed in the National Building Code of Canada. Then, the design methods proposed in Clause 27.10 of CSA S16-01 and its supplements Clause 27.11 and Annex M, both from CSA S16-14, are compared to identify differences and inconsistencies. Results This paper highlights the torsional sensitivity of headframes which generates significant shear in the direction perpendicular to the spectral acceleration application. Therefore, the design of mine headframes using the described methodologies shows significant differences since some are much more restrictive than others. The results are used to issue recommendations for further revision of Annex M such as the difficulty to use capacity design for headframe structures.

Keywords: Headframe, Seismic design, Dynamic analysis, Steel structures