| 摘要 |
According to the present invention, a second supplementary steel wire is inserted into a bottom casing concrete of a conventional ′steel wire tension preflex girder′ having preflexion restoring force and first steel wire tensile force of an I-type steel material for tension, and the fixing point of the second supplementary steel wire positioned on a line between preflexion points and on a girder section neutral axis. In addition, the second supplementary steel wire is arranged between the preflexion points in a form of a downward parabola, thereby the final compressive stress of a bottom casing between the preflexion points becomes maximum compressive stress, i.e. concrete allowable compressive stress (σca) by a total sum of the compressive stress introduced into the bottom casing by the preflexion restoring force of the I-type steel material, compressive stress introduced into the bottom casing by the tensile force of a first steel wire and a second supplementary steel wire, and tensile stress introduced into the bottom casing by girder self-weight. Accordingly, compressive stress, which has increased by at least 11 percent when compared to a compressive stress introduced into the lower central part of the bottom casing of the conventional ′steel wire tension preflex girder,′ may be introduced and reinforced. As a result, greater tensile stress can be resisted when compared to the conventional ′steel wire tension preflex girder′ of the same section such that structural performance is improved and an amount of the I-type steel material be saved to as much as the size of the increased tensile stress, thus facilitating effective and economical girder production. |
