Stability is one of the most critical problems in the design of welded metal structures, since in many cases instability causes failure or collapse of the structures. The present study aims to show the minimum mass design procedure for welded steel box columns loaded by a compression force. The normal stresses and overall stability are calculated for pinned columns. The dimensions of the box columns are optimized by using constraints on global stability, local buckling of webs and flanges. Different design rules and standards are compared: Eurocode 3, Japan Railroad Association, American Petroleum Institute, and American Institute of Steel Construction. The calculations are made for different loadings, column length and steel grades. The yield stress varies between 235 and 690 MPa. Optimization is carried out using the generalized reduced gradient method in Excel solver. Cost calculations and comparisons show the most economical structure.
) w y = C y L 2 8 = ϵ y L 2 8 y max = 143.43 ( mm ) , where y max = 190.89 (mm). Since the pre-bending deflection w P is less than the yield deflection. So the result is suitable. 6 Optimization for minimummass The optimization is made by the
The use of finite size sub-samples to derive elemental concentrations which are representative of a tissue or organ as a whole are subject to errors arising from the heterogeneous nature of biological specimens. Proton induced X-ray emission (PIXE) analysis is employed to identify element variances in porcine liver, kidney and heart and sampling factors, which are the minimum mass of sample required to reduce concentration variability to a given level, are calculated. This analysis highlights the inhomogeneous nature of biological specimens and the need for clearly defined sampling protocols.
, LTO is observed below 300 °C with the minimummass loss because of the fact that asphaltenes molecules are so heavy and resistant that oxygen does not affect this fraction until very high temperatures are reached. Reaction intervals and corresponding
Authors:J. I. Tobón, J. Paya, M. V. Borrachero, L. Soriano, and O. J. Restrepo
mass loss threshold, W max : 3 μg s −1 • Minimummass loss threshold, W min : 1 μg s −1 • Factor, f : 2 • Timeout, t : 6 s • Temperature range, 35–300 °C.
Results and discussion
Comparison between HRTG and