送交者: skywalker00 于 2005-8-08, 17:11:02:
回答: 三峡大坝危矣(伯克利熊博士曾参与的三峡大坝) 由 Enlighten 于 2005-8-08, 16:17:35:
I don't know what BerkeleyBear said, but prestressed concrete are much much stronger than regular one. see the following paragraph from Wikipedia:
Concrete has relatively high compressive strength, but significantly lower tensile strength (about 10% of the compressive strength). As a result, concrete always fails from tensile stresses - even when loaded in compression.
Concrete can also be prestressed using steel cables, allowing for beams or slabs with a longer span than is practical with reinforced concrete.