For a typical steel framed 30 ft by 30 ft office building bay, the fre-quency will be in the 5-8 Hz range. Frequency is a function of span (the longer the span, the lower the frequen-cy) and weight supported (the heavier the floor and the supported contents, the lower the frequency).
The following medical conditions are some of the possible causes of Skin color changes. There are likely to be other possible causes, so ask your doctor about your symptoms. 1  Causes of skin whitening:  Vitiligo.
Skin Diseases That Cause Dark Spots. 1  Melasma: Itâs one of the commonest causes of grayish patches on the face. 2  Riehlâs Melanosis: It causes grayish or brownish patches on your face resulting from hyper-pigmentation. 3  Poikiloderma of Civatte: This mostly affects the neck area that has been exposed to sunâs rays.