Simple planar modeling of asymmetric shear buildings for lateral forces

A simple plane frame model is described for the lateral load analysis—static and dynamic—of frames in multistory buildings including biaxial load effects. By taking advantage of the shear force-axial force and the torque-bending moment analogies it is possible to model the spatial behavior of the structure, and to consider the combined effects of bidirectional shear due to lateral and torsional displacements on columns pertaining to two orthogonal frames. A numerical example is given.     

Residual α–Si3N4 in O' Crystals in CeO2-Doped O'+β' SiAlON Ceramics

The microstructure of a pressureless sintered (1605°C, 90 min) O'+β' SiAlON ceramic with CeO₂ doping has been investigated. It is duplex in nature, consisting of very large, slablike elongated O' grains (20–30 μm long), and a continuous matrix of small rodlike β' grains (< 1.0 μm in length). Many α-Si₃N₄ inclusions (0.1–0.5 μm in size) were found in the large O' grains. CeO₂-doping and its high doping level as well as the high Al₂O₃ concentration were thought to be the main reasons for accelerating the reaction between the α-Si₃N₄ and the Si-Al-O-N liquid to precipitate O'–SiAlON. This caused the supergrowth of O' grains. The rapid growth of O' crystals isolated the remnant α–Si₃N₄ from the reacting liquid, resulting in a delay in the α→β-Si₃N₄ transformation. The large O' grains and the α-Si₃N₄ inclusions have a pronounced effect on the strength degradation of O'+β' ceramics.     

Effect of Zirconia Content on the Oxidation Behavior of Silicon Carbide/Zirconia/Mullite Composites

The oxidation of hot-pressed SiC-particle (SiC_p)/zirconia (ZrO₂)/mullite composites with various ZrO₂ contents, exposed in air isothermally at 1000° and 1200°C for up to 500 h, was investigated; an emphasis was placed on the effects of the ZrO₂ content on the oxidation behavior. A clear critical volume fraction of ZrO₂ existed for exposures at either 1000° or 1200°C: the oxidation rate increased dramatically at ZrO₂ contents of >20 vol%. The sharp transition in the oxidation rate due to the variation of ZrO₂ content could be explained by the percolation theory, when applied to the oxygen diffusivity in a randomly distributed two-phase medium. Morphologically, the composites with ZrO₂ contents greater than the critical value showed a large oxidation zone, whereas the composites with ZrO₂ contents less than the critical value revealed a much-thinner oxidation zone. The results also indicated that the formation of zircon (ZrSiO₄) at 1200°C, through the reaction between ZrO₂ and the oxide product, could reduce the oxidation rate of the composite.     

Phase and Property Studies of Boron Carbide–Boron Nitride Composites

Boron carbide–boron nitride particulate composites were fabricated by vacuum hot-pressing. Near-theoretical densities of B₄C were obtained, but percent theoretical densities decreased with increasing amounts of BN. The grain size of B₄C and BN was not affected by composition, but the amount of twinning in B₄C decreased with increasing BN content. No third phase was found at the B₄C–BN interface by analytical STEM analysis. Lattice parameter measurements indicated slight solubility of B₄C in BN, but no solubility of BN in B₄C for samples hot-pressed at 2250°C. Room-temperature flexural strength measurements revealed a sharply decreasing strength with increasing BN content up to 40% BN, and then relatively constant values with greater amounts of BN.     

Torsion of tube structures: Planar formulation

It is shown that the torsional analysis of tube structures can be performed directly by means of standard plane frame or plane stress finite element computer programs rather than by three-dimensional procedures. By considering in-plane rigidity of the floor slab and the presence of an elastic axis, it is shown that the only modifications required in these programs are the separate assembly of the stiffness submatrices of elements located at different distances from the axis, and the factoring of results by the distance ratios to a reference frame.     

A school-based emergency crisis intervention in a mass school disaster.

This article is a report detailing a coordinated crisis intervention undertaken in response to a disastrous collision of a railway train with a school bus. The target groups consisted of school-children, parents, and school staff. The effects of this mass disaster and the scope of the large-scale emergency intervention implemented in its wake are described. Emphasized are the role and importance of coordinated intervention in a mass emergency as a critical variable in (a) applying basic crisis intervention principles, (b) supervising intervention activities, and (c) implementing psychoeducational and short-term therapeutic procedures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dynamic torsional coupling in asymmetric building structures

An approximate method is proposed for the dynamic analysis of torsionally coupled tall building structures by utilizing the properties of their uncoupled counterparts. An exact solution is first given for the particular case in which the lateral and torsional stiffness matrices are uncoupled by same transformation. The method is then applied to a wider class of structures where this condition is only approximately satisfied by reducing the dynamic coupling problem to an approximate two-degrees-of-freedom system. Simple formulae and graphical representations of dynamic magnification of static eccentricity are given. Two numerical examples illustrate the use of the proposed method, checking on its accuracy and comparing its results with seismic code provisions.