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RE: Site specific response spectra[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaoc(--nospam--at)seaoc.org, shermanwc(--nospam--at)cdm.com (Bill Sherman)
- Subject: RE: Site specific response spectra
- From: Chris Palmateer <chrisp(--nospam--at)vlmk.com>
- Date: Mon, 18 May 1998 10:21:00 -0700
>2. However, if the intent of obtaining a site specific response spectrum is >to design for the potential of higher than code prescribed forces, >amplification of code values for elements should be considered. Since you state that you >are designing for increased base shear, it appears that it is your intent to >design for forces beyond code prescribed forces. (This is not uncommon for >critical structures.) In this case, I would consider the code element forces as minimum forces, >and I would calculate the acceleration at each level of >the structure from a dynamic analysis using the site specific response spectrum. >Then I would base the acceleration of each element on these results. (I would >divide the calculated acceleration by the R-factor for design.) > >Hope this helps. > This seems to be the logical thing to do. However, my questions stem from reading the recommendations in the Blue Book ('90 edition). In Section 1G.2 regarding lateral forces on elements of structures, there is a statement that reads,"The values of Cp listed in Table 1-H are for all elements and components (whether rigid or non-rigid) and for rigid equipment. It was not held to be necessary that the flexibility of elements and components be considered in design. THUS, ELEMENTS AND COMPONENTS NEED NOT BE CHECKED FOR POSSIBLE DYNAMIC AMPLIFICATION EFFECTS. This is because most such elements and components are either rigid or at least close to rigid." Does this mean that the current code equations are already over-conservative and "scaling up" the Fp is not necessary?
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