For example, those single taxpayers with $5,000 of Social Security benefits in the example above would see their marginal tax rate on nonâSocial Security income boosted by 50 percent if their modified AGI was between $25,000 and $30,000 and by 85 percent if their modified AGI was between $34,000 and $36,000.
Three types of vault were commonly used: the barrel-vault, the groined or four-part vault, and the dome. The barrel-vault was generally semi-cylindrical in section, and was used to cover corridors and oblong halls, like the temple-cellas, or was bent around a curve, as in amphitheatre passages.
It was superseded by the more flexible rib vaults of Gothic architecture in the later Middle Ages. Difficult to construct neatly because of the geometry of the cross groins (usually elliptical in cross section), the groin vault required great skill in cutting stone to form a neat arris.