Search

Abstract: The Sudbury Basin is a non-cylindrical fold basin occupying the central portion of the Sudbury Impact Structure. The impact structure lends itself excellently to explore the structural evolution of continental crust containing a circular region of long-term weakness. In a series of scaled analogue experiments various model crustal configurations were shortened horizontally at a constant rate. In mechanically weakened crust, model basins formed that mimic several first-order structural characteristics of the Sudbury Basin: (1) asymmetric, non-cylindrical folding of the Basin, (2) structures indicating concentric shortening around lateral basin termini and (3) the presence of a zone of strain concentration near the hinge zones of model basins. Geometrically and kinematically this zone corresponds to the South Range Shear Zone of the Sudbury Basin. According to our experiments, this shear zone is a direct mechanical consequence of basin formation, rather than the result of thrusting following folding. Overall, the models highlight the structurally anomalous character of the Sudbury Basin within the Paleoproterozoic Eastern Penokean Orogen. In particular, our models suggest that the Basin formed by pure shear thickening of crust, whereas transpressive deformation prevailed elsewhere in the orogen. The model basin is deformed by thickening and non-cylindrical synformal buckling, while conjugate transpressive shear zones propagated away from its lateral tips. This is consistent with pure shear deformation of a weak circular inclusion in a strong matrix. The models suggest that the Sudbury Basin formed as a consequence of long-term weakening of the upper crust by meteorite impact. [ABSTRACT FROM AUTHOR]

This paper addresses the design of wide-flange steel members subjected to torsional forces as well as axial forces and moments about their strong and weak axes. The current Canadian steel design standard (CSA S16-01) gives no specific guidance on methodology with respect to torsional design. Codes of other countries (American, British, Australian) provide useful insight but are different in format from the Canadian standard and cannot be used directly in conjunction with it. Specialized second-order finite element programs have the capacity for torsional analysis, but are too complicated and costly to use in design practice. There is, therefore, a need for a practical design method that would allow engineers to account for the effects of torsion simply and accurately. This paper, written by a practicing design engineer, suggests a number of approaches that, subject to discussion and approval by experts in the field, could constitute the basis for design of steel members in torsion. [ABSTRACT FROM AUTHOR]