A Minimum-Impact Method for Measuring Corrosion Rate of Steel-Hulled Shipwrecks in Seawater

Current research on USS Arizona is focused on a minimum-impact technique for calculating corrosion rate of the battleship's steel hull by analysing physical and chemical properties of marine encrustation covering the exposed hull. An equation is derived that allows concretion thickness, density, and total iron content to be used to calculate corrosion rate of steel hull plate.
© 2006 The Authors     

Internal oxidation of cast iron artifacts from an 18th-century steel cementation furnace

Heavily corroded metal artifacts recovered from the site of an 18th-century steel cementation furnace in Trenton, New Jersey, are cast iron altered by internal oxidation. The progress of the internal oxidation process was followed by comparison with the microstructure of cast iron exposed to high temperature in a wood-burning fireplace. The graphite flake structure of the cast iron allows deep, rapid penetration of oxygen that reacts at the iron–carbon interfaces within the iron to form iron oxides that eventually replace the graphite flakes. Microprobe analyses show that the silicon in the cast iron is converted to knebelite that also serves as the host for phosphorus. Sulfur dispersed in the internal oxidation product and porosity appear to be responsible for rapid rusting of the artifacts. Internal nitriding accompanies the oxidation. The Trenton artifacts are interpreted as grate bars from the fire box of a cementation furnace.     

SEISMIC BEHAVIOUR OF PERIMETER AND SPATIAL STEEL FRAMES

The present study deals with the seismic performance of partial perimeter and spatial moment resisting frames (MRFs) for low-to-medium rise buildings. It seeks to establish perimeter configuration systems and hence the lack of redundancy can detrimentally affect the seismic response of framed buildings. The paper tackles this key issue by com-paring the performance of a set of perimeter and spatial MRFs, which were “consistently designed”. The starting point is the set of low-(three-storey) and medium-rise (nine-storey) perimeter frames designed within the SAC Steel Project for the Los Angeles, Seattle and Boston seismic zones. Extensive design analyses (static and multi-modal) of the perimeter frame buildings and consistent design of spatial frame systems, as an alternative to the perimeter configuration, were conducted within this analytical study. The objectives of the consistent design are two-fold, i.e. obtaining fundamental periods similar to those of the perimeter frames, i.e. same lateral stiffness under design horizon-tal loads, and supplying similar yield strength. The seismic behaviour of perimeter and spatial configuration structures was evaluated by means of push-over non-linear static analyses and inelastic dynamic analyses (non linear time histories). Comparisons be-tween analysis results were developed in a well defined framework since a clear scheme to define and evaluate relevant limit states is suggested. The failure modes, either local or global, were computed and correlated to design choices, particularly those concerning the strength requirements (column overstrength factors) and stiffness (elastic stability indexes). The inelastic response exhibited by the sample MRFs under severe ground motions was assessed in a detailed fashion. Conclusions are drawn in terms of local and global performance, namely global and inter-storey drifts, beam and column plas-tic rotations, hysteretic energy. The finding is that the seismic response of perimeter and spatial MRFs is fairly similar. Therefore, an equivalent behaviour between the two configurations can be obtained if the design is “consistent”.     

基于社会网络分析方法的产业集群研究——以河南省虞城县南庄村钢卷尺产业集群为例

近年来,社会网络分析方法(SNA)被引入到产业集群研究中,它从更微观层次刻画了产业集群的网络结构和网络特性,在一定程度上弥补了当前产业集群研究的缺陷。但是SNA并不是深层次的结构模型,相应的分析还要从现象洞察到其背后社会关系的深层含义。本文首先对SNA作一简单介绍,然后以河南省虞城县南庄村钢卷尺产业集群为例,来检验这种分析方法在集群网络研究中的具体应用,并通过探究现象背后的社会关系来修正和完善这种分析方法,得出了重要结论,同时为丰富我国产业集群的研究方法提供有益参考。     

FRICTION DAMPED STEEL MOMENT-RESISTING FRAMES SUBJECTED TO LONG-DISTANCE EARTHQUAKES: INFLUENCE OF WELD FRACTURES

It has been generally accepted that steel moment-resisting frames behave in a ductile manner under seismic excitations. However, during the 1994 Northridge earthquake in California, weld fractures at the beam-to-column connections occurred in many steel buildings. Such brittle failures obviously precluded the traditional ductile-behaviour assumption and had a significant effect on the responses of steel moment-resisting frames. In this paper, the performance of a friction damping system for retrofitting steel moment-resisting frames was investigated under long-distance earthquakes. For this purpose, the 1985 Mexico City (SCT), the 1995 Bangkok, or the 1977 Romania ground motions, all scaled to a peak ground acceleration of 0.17 g, were considered in this study. Responses of the building under the 1940 El Centro N-S component were also included for comparison. The results of the study show that a friction damping system can reduce the seismic responses significantly. The devices can also prevent the total collapse and joint failures of the building equipped with friction dampers, while the one without dampers would collapse, even under a peak ground acceleration of only 0.17 g.     

Ukraine's Financial Crisis, 2009

A prominent specialist in the economic affairs of the former Soviet Union relates and analyzes the state of Ukraine's economy in light of a series of discussions and interviews with the country's Prime Minister and leading economic officials in Kyiv in 2008 and April 2009. The author, a former economic advisor to the country's government and co-chair of the UN's Blue Ribbon Commission for Ukraine, devotes this paper to a penetrating analysis of the impact of the global financial crisis of 2008-2009 on Ukraine's budget, banks, exchange rates, money supply, industrial sectors (particularly energy and steel), GDP, and inflationary pressures. Due attention is given to economic relations with the EU and Russia as well as to financial assistance from the IMF.Journal of Economic Literature, Classification Numbers: E500, E600, O520, P200. 1 table, 4 figures, 38 references.     

FATIGUE ANALYSIS OF MOMENT RESISTING STEEL FRAMES

A procedure for the fatigue assessment of steel building structures subjected to earthquakes is presented. The procedure constitutes an extension of the present, high-cycle, fatigue assessment to cases of low-cycle fatigue. It may serve as a basis for the introduction of a fatigue limit state in the earthquake design of steel structures. It may be also used for the damage assessment of existing steel buildings subjected to past earthquakes. By means of parametric studies, the effects of various parameters on the fatigue susceptibility of several moment resisting steel frames are studied. The influence of a number of parameters such as the type of ground motion, type of structural typology, local fatigue behaviour, overall frame design and semi-rigidity of joints on the susceptibility to damage are investigated.     

SEISMIC ENERGY DEMAND IN STEEL MOMENT FRAMES

The present paper investigates the seismic energy demand in steel moment-resisting frames. The frames, with 3, 6 and 10 storeys, and 4 and 8 spans, are designed according to current seismic code provisions. The energy response (energy quantities and their distributions) in the frames subjected to an ensemble of six earthquake ground motions recorded on different soil conditions, is investigated by nonlinear time history analysis. The study concludes that (1) the results of energy response can be developed into a rational method of seismic evaluation and design for steel moment-resisting frames; (2) the energy concept based on the single-degree-of-freedom has limitations when extended to the realistic structural system for design purposes; and (3) it is necessary to develop the energy-based approach for seismic evaluation and design based on the seismic response of a realistic multi-degree-of-freedom structural system.