Preventing Cracking at Diaphragm/Plate Girder Connections in Steel Bridges, HR-393, 1998

Some of the Iowa Department of Transportation (Iowa DOT) continuous, steel, welded plate girder bridges have developed web cracking in the negative moment regions at the diaphragm connection plates. The cracks are due to out-of-plane bending of the web near the top flange of the girder. The out-of-plane bending occurs in the "web-gap", which is the portion of the girder web between (1) the top of the fillet welds attaching the diaphragm connection plate to the web and (2) the fillet welds attaching the flange to the web. A literature search indicated that four retrofit techniques have been suggested by other researchers to prevent or control this type of cracking. To eliminate the problem in new bridges, AASHTO specifications require a positive attachment between the connection plate and the top (tension) flange. Applying this requirement to existing bridges is expensive and difficult. The Iowa DOT has relied primarily on the hole-drilling technique to prevent crack extension once cracking has occurred; however, the literature indicates that hole-drilling alone may not be entirely effective in preventing crack extension. The objective of this research was to investigate experimentally a method proposed by the Iowa DOT to prevent cracking at the diaphragm/plate girder connection in steel bridges with X-type or K-type diaphragms. The method consists of loosening the bolts at some connections between the diaphragm diagonals and the connection plates. The investigation included selecting and testing five bridges: three with X-type diaphragms and two with K-type diaphragms. During 1996 and 1997, these bridges were instrumented using strain gages and displacement transducers to obtain the response at various locations before and after implementing the method. Bridges were subjected to loaded test trucks traveling in different lanes with speeds varying from crawl speed to 65 mph (104 km/h) to determine the effectiveness of the proposed method. The results of the study show that the effect of out-of-plane loading was confined to widths of approximately 4 in. (100 mm) on either side of the connection plates. Further, they demonstrate that the stresses in gaps with drilled holes were higher than those in gaps without cracks, implying that the drilling hole technique is not sufficient to prevent crack extension. The behavior of the web gaps in X-type diaphragm bridges was greatly enhanced by the proposed method as the stress range and out-of-plane distortion were reduced by at least 42% at the exterior girders. For bridges with K-type diaphragms, a similar trend was obtained. However, the stress range increased in one of the web gaps after implementing the proposed method. Other design aspects (wind, stability of compression flange, and lateral distribution of loads) must be considered when deciding whether to adopt the proposed method. Considering the results of this investigation, the proposed method can be implemented for X-type diaphragm bridges. Further research is recommended for K-type diaphragm bridges.

HG 393.60-393.85

Brown sediment with clasts that range from small to large. The clast shape ranges from angular to sub-rounded. Lineations and water escape structures are present. Grain crushing and minor amounts of rotation are also present.

Estudio respirométrico de Lactobacillus casei ATCC 393 en presencia de iones Cu (II) y Zn (II)

Tesis (Maestría en Ciencias con Especialidad en Microbiología Industrial) UANL

Les diplômés – no 393, automne 1997

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A cyclic bipolar wind in the interacting binary V 393 Scorpii

V393 Scorpii is a double periodic variable characterized by a relatively stable non-orbital photometric cycle of 253 d. Mennickent et al. argue for the presence of a massive optically thick disc around the more massive B-type component and describe the evolutionary stage of the system. In this paper, we analyse the behaviour of the main spectroscopic optical lines during the long non-orbital photometric cycle. We study the radial velocity of the donor determining its orbital elements and find a small but significant orbital eccentricity (e = 0.04). The donor spectral features are modelled and removed from the spectrum at every observing epoch using the light-curve model given by Mennickent et al. We find that the line emission is larger during eclipses and mostly comes from a bipolar wind. We also find that the long cycle is explained in terms of a modulation of the wind strength; the wind has a larger line and continuum emissivity at the high state. We report the discovery of highly variable chromospheric emission in the donor, as revealed by the Doppler maps of the emission lines Mg II 4481 and C I 6588. We discuss notable and some novel spectroscopic features like discrete absorption components, especially visible at blue depressed O I 7773 absorption wings during the second half-cycle, Balmer double emission with V/R curves showing 'Z-type' and 'S-type' excursions around secondary and main eclipses, respectively, and H beta emission wings extending up to +/- 2000 km s(-1). We also discuss possible causes for these phenomena and for their modulations with the long cycle.

Na 50 Nachlass Arthur Schopenhauer - 'Schopenhauer-Archiv', 393 - Auszug aus dem Totenbuch der Freien Stadt Frankfurt am Main

u.a.: bezeugt durch den Appellationsgerichtssekretär Dr. jur. Gwinner und den Arzt Dr. med. Stiebel; Arthur Schopenhauer;