1887

oa Civil Engineer in South Africa - The interaction between openings in - the webs of steel beams : technical paper

 

Abstract

The interaction between adjacent rectangular openings in the webs of steel I-beams is investigated. The perforated section is considered in terms of its equivalent line structure, and from an analysis of elastic deformations a design curve is developed for determining the critical width of the web post between openings. The transition in failure modes of the perforated section occurs at this width, viz from independent failure (involving only one opening) to interactive failure (involving both of the openings and the intervening web post).


The reduction in the ultimate strength of a beam section due to the presence of adjacent web openings will be minimized if the designer can ensure that independent failure occurs. The practical significance of the critical width is thus that it defines the minimum width of web post that must be used if the perforated section is not to be unduly weakened. The validity of the design curve is verified by an independent determination (using plastic analysis) of the critical widths of web posts for a range of practical beams. It is also shown to predict correctly the modes of failure of a number of experimental beams.

Die wisselwerking tussen aangrensende reghoekige openinge in die webplate van staal I-balke word ondersoek. Die geperforeerde seksie is in terme van sy ooreenkomstige lynstruktuur in oenskou geneem en aan die hand van 'n ontleding van die elastiese vervormings is 'n ontwerpskromme, vir die berekening van die kritieke wydte van die webpaal tussen aangrensende openinge, ontwikkel.


Op hierdie wydte vind daar 'n oorgang van die falingsmodusse van die geperforeerde seksie plaas, nl van onafhanklike faling (waarby slegs een opening betrokke is) na interaktiewe faling (waarby altwee die openinge sowel as die tussenbeidetredende webpaal betrokke is). Die vermindering in die uiteindelike sterkte van 'n balk, as gevolg van die aanwesigheid van webopeninge, sal geminimiseer word indien die ontwerper kan verseker dat die onafhanklike falingsmodus plaasvind. Die praktiese belang van die kritieke wydte is gevoiglik dat dit die minimum wydte van webpale, wat gebruik moet word om te verseker dat die geperforeerde seksie nie onnodig verswak word nie, afbaken.
Die geldigheid van die ontwerpskromme is bevestig, deur middel van onafhanklike bepalings (wat van plastiese vervormingsanalise gebruik maak) van die kritieke wydtes van die webpale, vir 'n reeks praktiese balke. Daar word ook aangetoon dat falingsmodusse van 'n aantal eksperimentele balke, met behulp van die ontwerpskromme, korrek voorspel kan word.

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/content/civeng1/30/5/EJC25078
1988-05-01
2016-12-09
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