Four columns bear load from vaulting above. There are two semi-circular arch across the ceiling and with gothic, pointed arches on four faces it forms a line between the arch peaks and vaulting that is usually filled with rubble.
Early Egyptians and Greeks had only stone lintels, which had a limited tensile strength so distances spanned could only be relatively small. The Romans developed the semi-circular arch. Load is transferred down through constant columns to ground. As the arch is loaded, the stone will tighten up and bear greater load.
Concrete is strong in compression, however is generally weak in tension. Therefore when a load is placed upon it it may bend. To make sure this doesn’t happen, steel reinforcement is put in on the tensile face, normally the bottom edge if a floor or beam.
Tension can also occur outwards, so for example a basement [...]
