Experimental study on the behaviour of steel columns under seismic-induced axial impact load

It has been observed during major earthquakes that the so called soft-storey failure of an upper floor of a structure results in large impact load acting on structural members of the lower storeys. It may further lead to progressive collapse of the whole structure substantially intensifying human and material losses. Therefore, the aim of this paper is to investigate experimentally the behaviour of columns under bending (observed during an earthquake) that are additionally subjected to an axial plastic impact load. Steel columns with high slenderness ratio were considered in the study. In the experiment, impact load was created by a weight that was dropped onto the top of the column and stayed on it. The weight with the shape of a ball was made of clay so as to simulate more plastic impact. The results of the experiment show that the value of the permanent horizontal deformation of the column observed after impact depends much on the initial relative displacement between the base and the top of the column. As the initial displacement increases the values of the permanent deformation increases significantly indicating the significant reduction in the critical buckling force. The results obtained in the study can be utilized at the design stage of the structures in order to enhance their seismic resistance. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Monotone Iterations for First Order Differential Equations with a Parameter

The method of lower and upper solutions is useful to show that a differential problem has a solution. In this paper we use this technique to a differential problem with a parameter. Some existence results are formulated under the assumption that the corresponding functions satisfy the one-sided Lipschitz condition.     

Systems of Differential Inequalities with Initial Time Difference

Some comparison results are formulated for systems of differential inequalities with different initial points.     

Multipoint Boundary Value Problems for Odes. Part II

We apply the method of quasilinearization to multipoint boundary value problems for ordinary differential equations showing that the corresponding monotone iterations converge to the unique solution of our problem and this convergence is quadratic.     

Stereocontrolled synthesis of imidazolo[1,5]hexopiperidinoses and imidazol-4(5)-yl-C-glycosides

The syntheses of imidazolo[1,5]hexopiperidinoses 2-6 and imidazol-4(5)-yl C-glycosides 7-9 are reported. The crucial step of this approach relies upon the S_N2-type cyclisation of selectively protected C(1), C(2), C(3) and C(5)-substituted 1-[imidazol-4(5)-yl]pentitols in which the imidazole nitrogen or the C(1)-connected oxygen are involved as the competitive nucleophilic centers, respectively. Six selected imidazolosugars were evaluated as potential inhibitors of glycosidases.     

Multiple solutions of coupled-cluster doubles equations for the Pariser–Parr–Pople model of benzene

To gain some insight into the structure and physical significance of the multiple solutions to the coupled-cluster doubles (CCD) equations corresponding to the Pariser–Parr–Pople model of cyclic polyenes, complete solutions to the CCD equations for the ¹A _1g ^- states of benzene are obtained by means of the homotopy method. By varying the value of the resonance integral ß from –5.0 to –0.5 eV, we cover the so-called weakly, moderately, and strongly correlated regimes of the model. For each value of ß, 230 CCD solutions are obtained. It turned out, however, that only for a few solutions a correspondence with some physical states can be established. It has also been demonstrated that, unlike for the standard methods of solving CCD equations, some of the multiple solutions to the CCD equations can be attained by means of the iterative process based on Pulay's direct inversion in the iterative subspace approach.     

Prediction of turbulent source flow between stationary and rotating discs

Results are presented from a numerical investigation of turbulent source flow between two discs, both of which are stationary or corotating. Parabolic flow was assumed and the Box Method used to obtain marching solutions of the governing equations. Turbulence modelling was based on extensions of classical eddy-viscosity/mixing-length concepts which reflect the influences of divergence of the mean-flow streamlines and non-isotropic Reynolds stresses due to disc rotation. The predictions for the rotating case are the first local results available. For the stationary case, earlier work has been extended by the use of empirical formulae for reverse transition and inclusion of the influence of streamline divergence. Comparisons with limited data for stationary and corotating discs show reasonable agreement. Although the turbulence models are probably not optimum, they provide an adequate basis for engineering studies of turbulent source flow between corotating and stationary discs until more extensive and reliable empirical information is available.     

Model study of the impact of orbital choice on the accuracy of coupled-cluster energies. I. Single-reference-state formulation

The impact of the choice of molecular orbital sets on the results of single-reference-state coupled-cluster (CC) methods was studied for the H4 model. This model offers a straightforward way of taking into account all possible symmetry-adapted orbitals. Moreover, the degree of quasi-degeneracy of its ground state can be varied over a wide range by changing its geometry. The CCD, CCSD, and CCSDT approaches are considered. Surfaces representing the dependence of the energy on the parameters defining the orbitals are obtained. It is documented that for every method there exist alternative orbital sets which allow one to obtain more accurate energies than the standard (HF, BO, and NO) ones. However, for many of the former orbital sets, one obtains relatively large one-body amplitudes or one may encounter problems with solving the CC equations by conventional methods. An interesting variety of orbitals which might be useful for studies of quasi-degenerate states by the CCD method was found. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 205–219, 1998