Rhythmic staged prestressed concrete bridge forwarding - using stress members periodically providing eccentric stresses for alternating moment absorption

摘要

Erection of prestressed concrete bridges, involves making sections in a nearby fixed formwork and forwarding them in a rhythmic sequence, each new one being joined to its predecessor by prestressed connecting reinforcement rods, so as to provide continuous central or constantly eccentric stressing. During forwarding, provision is made for absorption of alternating moments at one or both edges by stress members (7, 8) with lengthways interrupted prestressing forces passed through them. These are repeatedly relaxed, withdrawn and re-stretched, acting against the forwarding direction, so that counteracting, temporary and eccentric prestressing forces are always present in the interval when they are needed. This is much less expensive than use of temporary auxiliary piers.