Partially prestressed concrete

摘要

Partial prestressing, which fills the gap between fully prestressed concrete and reinforced concrete, has now been accepted and become normal practice in many regions. The research and development of partially prestressed concrete members with bonded and unbonded tendons made of steel as well as fibre-reinforced polymer (FRP) are reviewed. The behaviour of bonded partially prestressed concrete members has been extensively studied, and this review mainly focuses on fatigue behaviour, serviceability analysis and time-dependent effects. The research on unbonded partially prestressed concrete members has mainly focused on prediction of flexural resistance, which is closely related to the ultimate tendon stress at flexural failure. Investigations of the service and ductility behaviour of unbonded partially prestressed concrete members are comparatively limited. Although external prestressing is effective in strengthening flexural concrete members, the strength acquired is accompanied by a reduction in ductility of flexural failure. The amount of prestressing tendons should therefore be carefully chosen to maintain the necessary ductility of the strengthened members. When FRP tendons are used in partially prestressed concrete members, deformability is a key indicator of safety.