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Re: LRFD Load Factors.[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: Re: LRFD Load Factors.
- From: "Maurice J. Allgrove" <malgrove(--nospam--at)daffodil.InfoChan.COM>
- Date: Thu, 19 Nov 1998 19:24:49 -0500
The long and short of the answer to your question is technically IMHO ..... no. In Jamaica we use primarily British Codes (Limits States = LRFD), however depending on the source of funding for various projects, we may end up using American, Canadian or British CP. The Load factors as you rightfully point out are geographically, and environmentally specific (eg. How rigidly are local statutes enforced with regard to No.s of ppl in a dance area, allowable axle weights etc), the resistance factors (partial factors of safety), are another matter, especially as it relates to concrete, and timber (ie materials which tend to have less quality control than say steel). The final point is Load Factors, as presented in the codes are essentially guidelines, and do not serve as carte blanche figures to be applied, because at the end of the day what governs is engineering judgment, as sound as we can make it. I don't know what the construction environment is in Peru, but I do know from at least a Jamaican perspective, what applies here, I know is quite different from what the CP envisaged. Additionally, modern CP's (Code of Practice), are also related to expected levels of risk (I'm not sure of the specifics of the American Code) which are related to expected return periods (eg 1:100, 1:25, 1:50 etc depending on the CP). ( I'm not sure I agree with the premise, because a 1:100 yr event can occur in year two .. explain that to a client, but that's another discussion altogether :-)). These are all things which I think need to be borne in mind, when using the CP out of it's intended environment (and to a degree, even in it's intended environment). The quick answer after all of that verbiage (IMHO) is use the provided values as guidelines and adjust up (or even down) as you can reasonably determine, in lieu of hard data (if it's available .all the better :-)). What we do, is however, as a project is ongoing we statistically analyse available data (cube, cylinder tests etc), and examine how close the values are to the expected figures and reanalyse the system :-) I hope I've been more of a help than a hinderance Maurice J. Allgrove, PE
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