Seismic damage estimation of in-plane regular steel moment resisting and x-braced frames

Simple empirical expressions to estimate maximum seismic damage on the basis of five well known damage indices for planar regular moment resisting and x-braced steel frames are presented. They are based on the results of extensive parametric studies concerning the inelastic response of a large number of these frames to a large number of ground motions. Thousands of nonlinear dynamic analyses are performed by scaling the seismic records to different intensities in order to drive the structures to different levels of inelastic deformation and finally to collapse. The statistical analysis of the created response databank indicates that the number of stories, period of vibration, stiffness ratio, capacity factor (for moment resisting frames), brace slenderness ratio and column stiffness (for x-braced frames) and characteristics of the ground motion, such as characteristic period and spectral acceleration, strongly influence damage. Nonlinear regression analysis is employed in order to derive simple formulae, which reflect the influence of the aforementioned parameters and offer a direct estimation of the damage indices used in this study. More specifically, given the characteristics of the structure and the ground motion, one can calculate the maximum damage observed in column bases and beams (for moment resisting frames) or in braces (for x-braced frames). Finally, two examples serve to illustrate the use of the proposed expressions and demonstrate their accuracy and efficiency. © 2012 Springer Science+Business Media Dordrecht

Experimental and numerical investigation of high-yield grout ore pass plugs to resist impact loads

In the last fifteen years, Tekseal high yield foaming grout ore pass plugs that could later be easily removed, have been poured above chute maintenance areas providing protection from high energy rock impact and isolating workers from the hazard. Construction and removal methods will be briefly explained. Since it is not economically feasible to investigate the problem of ore pass plug impact response using full-scale experimental studies, this paper presents a combined four-stage approach that includes (1) laboratory testing to investigate the mechanical behaviour of the high-yield foaming grout; (2) high-precision impact testing of reduced-scale models of ore pass plugs; (3) high-fidelity physics-based numerical model calibration using experimental data; and (4) full-scale modelling of mine ore pass plugs using calibrated material models. To calibrate numerical models, three one-metre diameter steel pipes filled with Tekseal high yield foaming grout were tested with falling steel projectiles of different shapes. Impact tests provided data on the depth of penetration and size of the craters formed by the projectiles. Numerical models were calibrated by optimising the material parameters and modelling techniques to provide the best match with the experimental results. Full-scale numerical models of ore pass plugs were developed for typical ore pass dimensions and subjected to impact events by falling rock projectiles. The proposed approach has allowed investigating energy absorbing characteristics of ore pass plugs to further predict and increase understanding of their capacity to withstand high-speed impacts by large falling projectiles. © 2014 Elsevier Ltd