R/R: Repair and Rehabilitation of Nonductile R.C. Frames Using High Performance Fiber Reinforced Cement Composites

摘要：在美国地震区建造的旧钢筋混凝土框架结构通常是非延性的，因此被认为是危险的。 实验室研究表明，在新建筑中使用“普通”纤维增强混凝土（FRC）可以显著改善地震响应，但传统的抗震加固技术尚未利用FRC或高性能FRC（HPFRC）。 与传统钢筋混凝土相比，FRC的优点是延性显著增加。 HPFRC的优点是，当加载超过弹性极限时，这些材料在失效前经受应力和应变进一步增加的能力方面表现出显著的改善。 这种抗拉强度和延展性的增加导致结构框架耗散能量的能力的巨大增加，这是抗震设计特别需要的特征。 * 本研究项目的目标是开发一种创新技术，用于非延性钢筋混凝土框架的抗震加固，使用最近开发的HPFRC，其在非弹性范围内表现出复合应变和应力能力的显着增加。 使用这种材料可以解决钢筋混凝土框架的以下常见问题：（1）梁中不连续底部钢筋的锚固不足，（2）柱搭接接头的限制不足，以及（3）接头的限制不足。 该研究为新型高性能聚合物纤维混凝土复合材料在非延性结构抗震加固中的应用开辟了新的领域。 该项目得到了美国国家科学基金会（NSF）倡议“结构抗震修复和恢复研究”的支持。"***

ABSTRACT: Older reinforced concrete frame structure constructed in seismic areas of the United States are usually non-ductile and are thus identified as hazardous. Laboratory studies have shown that the use of "ordinary" Fiber Reinforced Concrete (FRC) in a new construction has substantially improved seismic response, but conventional seismic retrofit techniques have not yet taken advantage of FRCs or High Performance FRCs (HPFRCs). The advantage of FRCs is a significant increase in ductility over that of conventional reinforced concrete. The advantage of HPFRC is that, when loaded beyond the elastic limit, these materials exhibit a significant improvement in the ability to undergo further increase in stress and strain before failure. This increase in tensile strength and ductility leads to an enormous increase in ability of the structural frame to dissipate energy-a feature particularly desirable for earthquake-resistance design. ***The goals of this research project herein is to develop an innovative technique for seismic retrofit of nonductile reinforced concrete frames using recently developed HPFRCs which exhibit significant increase in the composite strain and stress capacity in the inelastic range. Use of this material can solve the following common problems of reinforced concrete frames: (1) Inadequate anchorage of the discontinuous bottom reinforcement in beams, (2) inadequate confinement of the column lap splices, and (3) inadequate confinement of the joint. The research is expected to open up a new area for seismic repair and rehabilitation of non-ductile structures by using newly developed HPFRC composites. The project is supported under NSF Initiative "Repair and Rehabilitation Research for Seismic Resistance of Structures."***