Tests on light gage steel diaphragms

This report supplements and extends the scope of Report No. 319, ;lStructural Performance of Light Gage Steel Diaphragms , by Dr. Larry D. Luttrell. Eleven static load tests were conducted on 22 gage narrow rib roof decks to investigate the effect of length of the diaphragm, type of welding, and diaphragm material tensile properties on the shear stiffness and strength of the diaphragm. The behavior of a diaphragm under reversed load at two different levels) one at 0.4 x ultimate static load and the other at 0.6 x ultimate static load was explored by conducting five tests. The tests at a high level of reversed load (0.6 x Pu) were motivated by the fact that during earthquakes and blasts structures are subjected to high levels of reversed load for a few cycles. Three static load tests were performed on standard corrugated diaphragms to supplement the tests done by Dr. Luttrell and reported in Report No. 319 so as to formulate the strength (Plf.) of a diaphragm without intermediate fasteners* as a function of its thickness. It is confirmed by the above investigations that the shear stiffness of a diaphragm is dependent mainly on the length of the diaphragm, and the type and spacing of fasteners. The strength of a diaphragm is seen to be dependent mainly on the thickness of the diaphragm, and the type and spacing of the • The definition is the same as in Report 319. fasteners. Five cycles of reversed load at +0.6 x ultimate load of an identical diaphragm under static load resulted in a maximum reduction of 25% in strength of the diaphragm

Design of I-shaped beams and columns with diaphragm bracing

Cold-formed steel panels often are used as wall sheathing, roof decking or floor decking in steel framed buildings or pre-engineered metal buildings. Diaphragms formed by interconnecting these panels have considerable in-plane shear resistance, and can be utilized as bracing against buckling for individual members of a steel frame. For wall columns the diaphragm may be either directly attached or connected to girts which in turn are connected to the columns. A procedure is presented for the design of I-section beams and columns with diaphragm or diaphragm-girt bracing. The procedure is based on the ultimate load capacity of fully braced members, utilizing a conservative estimate of the shear strength and shear rigidity of the diaphragm. Design examples are included. The utilization of existing wall, floor or roof diaphragms as bracing for individual beams and columns can eliminate the need for other types of bracing, and/or reduce required member sizes. Thus it contributes to economical design

Design recommendations for diaphragm-braced beams, columns and wall-studs

INTRODUCTION Light gage steel panels are often used as wall sheathing, roof decking or floor covering in steel framed buildings. These panels carry loads normal to their plane by virtue of their bending strength. Also, diaphragms formed by interconnecting such panels can resist shear deformation in their plane. Because of this shear resisting capacity, diaphragms can be very effective in bracing columns and beams of a steel frame against lateral buckling and, thus, increase the load carrying capacity of these members. For wall columns, such diaphragm bracing may be either directly attached or connected to girts which in turn are connected to the columns. The ribs of the panels must be perpendicular to the members to which they are attached. These diaphragms as wall, roof or floor, must be present in any event, and therefore, are available at no extra cost. If properly utilized for bracing, they can lead to economical design of beams and columns. Research has been conducted at Cornell University since 1961* (1),(2),(3) to determine the increased load carrying capacities of beams and columns due to diaphragm or diaphragmgirt bracing. Based on the results of the investigation to date, recommendations are made in this report for the design of beams and columns considering the effect of diaphragm braci~g. * Superscripts in parentheses refer to the numbers in the References. Design criteria are given in Part 2; the general design procedure in Part 3, and the specific design formulae in Part 4 are illustrated by some practical examples in Part 5. The design procedure suggested herein is based on the ultimate load capacity of the beams or columns, utilizing a conservative estimate of the strength and rigidity of the diaphragm bracing. Effectiveness of diaphragm bracing or diaphragm-girt bracing in preventing lateral buckling of beams and columns depends on its two fundamental characteristics: (1) rigidity, and (2) strength. In general, it is not economical to provide anything less than fUll bracing, where full bracing is defined as bracing such that any increase in rigidity or strength of diaphragm will not cause any substantial increase in the load carrying capacity of the braced members. Therefore, the design procedure in this report is limited to only fullyli braced beams and columns. The procedure is based on analyses of I-section beams under uniform moment, and I-section columns under axial load. These analyses have been substantiated by tests of thirtyfive diaphragm-braced assemblies as reported in the references. Information regarding the load carrying capacities of beams and columns with less than full bracing can be obtained from Reference 3. The capacity of channel and Z-section beams SUbjected to uniform moment also is discussed in Reference 3. Cantilever beams and channel and Z-section beams subjected to loads in the plane of the web are currently under investigation. Light wall studs braced by wallboard on one or both faces are no different basically from columns braced by light steel diaphragms. In order to make the methods developed here applicable to such wall studs, the Appendix gives a few typical test values for diaphragm rigidity and strength of customary types of wallboard

A Decade in the Life of EXO 2030+375: A Multi-wavelength Study of an Accreting X-ray Pulsar

Using BATSE and RXTE observations from 1991 April to 2001 August we have detected 71 outbursts from 82 periastron passages of EXO 2030+375, a 42-second transient X-ray pulsar with a Be star companion, including several outbursts from 1993 August to 1996 April when the source was previously believed to be quiescent. Combining BATSE, RXTE, and EXOSAT data we have derived an improved orbital solution. Applying this solution results in a smooth profile for the spin-up rate during the giant outburst and results in evidence for a correlation between the spin-up rate and observed flux in the brighter BATSE outbursts. Infrared and Halpha measurements show a decline in the density of the circumstellar disk around the Be star. This decline is followed by a sudden drop in the X-ray flux and a turn-over from a spin-up trend to spin-down in the frequency history. This is the first Be/X-ray binary which shows an extended interval, about 2.5 years, where the global trend is spin-down, but the outbursts continue. In 1995 the orbital phase of EXO 2030+375's outbursts shifted from peaking about 6 days after periastron to peaking before periastron. The outburst phase slowly recovered to peaking at about 2.5 days after periastron. We interpret this shift in orbital phase followed by a slow recovery as evidence for a global one-armed oscillation propagating in the Be disk. This is further supported by changes in the shape of the Halpha profile which are commonly believed to be produced by a reconfiguration of the Be disk. The truncated viscous decretion disk model provides an explanation for the long series of normal outbursts and the evidence for an accretion disk in the brighter normal outbursts.Comment: 24 pages, 11 figures, accepted for publication in Ap

Observations of Accreting Pulsars

We summarize five years of continuous monitoring of accretion-powered pulsars with the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory. Our 20-70 keV observations have determined or refined the orbital parameters of 13 binaries, discovered 5 new transient accreting pulsars, measured the pulsed flux history during outbursts of 12 transients (GRO J1744-28, 4U 0115+634, GRO J1750-27, GS 0834-430, 2S 1417-624, GRO J1948+32, EXO 2030+375, GRO J1008-57, A 0535+26, GRO J2058+42, 4U 1145-619 and A 1118-616), and also measured the accretion torque history of during outbursts of 6 of those transients whose orbital parameters were also known. We have also continuously measured the pulsed flux and spin frequency for eight persistently accreting pulsars (Her X-1, Cen X-3, Vela X-1, OAO 1657-415, GX 301-2, 4U 1626-67, 4U 1538-52, and GX 1+4). Because of their continuity and uniformity over a long baseline, BATSE observations have provided new insights into the long-term behavior of accreting magnetic stars. We have found that all accreting pulsars show stochastic variations in their spin frequencies and luminosities, including those displaying secular spin-up or spin-down on long time scales, blurring the conventional distinction between disk-fed and wind-fed binaries. Pulsed flux and accretion torque are strongly correlated in outbursts of transient accreting pulsars, but uncorrelated, or even anticorrelated, in persistent sources.Comment: LaTeX, psfig, 90 pages, 42 figures. To appear in Dec. 1997 ApJS, Vol 113, #

Problems in structural diaphragm bracing 1. Beams continuously braced by diaphragms 2. I-section columns braced by girts and a diaphragm

Shear-resistant light-gage metal diaphragms can be very effective in increasing the load carrying capacity of beams continuously braced by diaphragms, or of columns braced by girts which in turn are braced by diaphragms, if proper connections are made between the individual elements. In this thesis, behavior of diaphragm-braced I-beams, channel beams, and Z-beams under uniform moments, and the behavior of axially loaded I-section columns braced by girts which in turn are braced by diaphragms are investigated. Load-deflection relationships of diaphragm-braced beams are obtained taking into consideration the initial imperfections of the beams and using the equilibrium method. Critical moments of diaphragm-braced beams are derived from the loaddeflection relationships by letting the initial imperfections equal zero and solving the resulting eigenvalue problem. A procedure to determine the load carrying capacities of diaphragm- braced beams is given using an assumed criteria of failure for beams and diaphragms. Using the above procedure, load carrying capacities of diaphragm-braced beams are calculated in two examples; they range from 80% to 85% of the corresponding critical moments. A test was conducted on an assembly of four diaphragmbraced I-beams, and the moment sustained by the beams was 10% smaller than the predicted critical moment. Three tests were and the moments sustained by the beam assemblies ranged from 75% to 99.6% of the corresponding critical moments. Tests conducted on assemblies of two diaphragm-braced I-beams are also reported here. In general, the experimental and predicted load deflection relationships are in fairly good agreement for both diaphragm-braced I-beam and channel beam assemblies. Load-deflection relationships of columns braced by girts and diaphragms are obtained taking into consideration the initial imperfections of the columns and using the energy method. The Rayleigh-Ritz technique is used to obtain an approximate solution. Similar to the case of beam assemblies, critical loads of column assemblies are derived from the load-deflection relationships. A procedure to determine the load carrying capacity of columns braced by girts and diaphragms is given using assumed criteria of failure of columns, girts, and diaphragms. Using the above procedure, load carrying capacities of two different wall columns are calculated and they.range from 68% to 83% of the corresponding critical loads. Three tests were conducted on columns braced by two intermediate girts which in turn were braced by diaphragms, and the failure loads of the column assemblies ranged from 84% to 94% of the corresponding critical loads. Fully flexible, fully rigid, and semi-rigid girt-column connections were used in the . three tests. The experimental and theoretically predicted load-deflection relationships are in fair agreement. Theoretical solutions for diaphragm-braced beams and for columns braced by girts and diaphragms were developed first in the elastic range and then extended to the inelastic range by suitably modifying the elastic modulii. The plastic moment of the beams or the Euler buckling load of the columns between successive girts appears to be theoretically attainable by using the diaphragm bracing

Near-infrared bands of S<SUB>2</SUB>:<SUP>3</SUP>&#928;<SUB>gi</SUB>-<SUP>3</SUP>&#931;<SUB>u</SUB><SUP>+</SUP> system

Vibrational and rotational analyses of the near-infrared bands of S2 lying in the region 7440–8085&#197; are reported. They form a new band system involving a S2:3&#928;gi-3&#931;u+ transition and arise from the same initial 3&#928;gi state of the 3&#928;gi-3&#916;ui band system reported earlier. The analyses of the bands of this system due to the isotopic molecules 32S34S and 34S2 are also reported

Near-infrared photometry of RS CVn systems and candidates

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Near-infrared photometry of unidentified EIC-1 sources

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