（福州大学土木工程学院，福州 350002）
［摘要］进行了从某公路桥拆下的两根空心板梁现场足尺试验，采用裂缝宽度测试仪、应变片和导杆引伸仪三种方法来确定消压荷载，采用简化弹性方法计算现存预应力，以受压区混凝土破坏为破坏准则来确定极限荷载。采用应变片方法来确定消压荷载最具有重复性和可靠性，采用裂缝宽度测试仪方法来确定消压荷载偏于不安全；按现行公路桥规（JTG D62—2004）中确定预应力损失的方法计算预应力筋相应的各种损失，对试件的开裂荷载、消压荷载、现存预应力和极限荷载进行理论计算；实测结果与理论计算结果基本吻合，可为既有预应力混凝土梁现存预应力和极限荷载的确定提供参考。
［关键词］现存预应力；开裂荷载；消压荷载；极限荷载
Evaluation of effective prestress force and ultimate load in prestressed concrete beams
Chen Yong，Fang Zhenzheng(Engineering Education in Fuzhou University, Fuzhou 350002，China)
Abstract:The results of an experimental study to determine the effective prestress force in two full-scale prestressed void floor-beams are presented. Three methods are used to determine the decompression load: 1) visual observation of crack opening, 2) strain gauges, 3) displacement transducers. The effective prestress force is calculated by the simple elastic method through the decompression load near the cracks. The ultimate load is determined through the failure occurred by crushing of the concrete in the compression zone. The result of the experiment presents that the decompression loads obtained from the strain gauges are found to be repeatable and reliable in the three methods. It also presents that it is not safe to determine the decompression load by visual observation of crack opening. Based on the -Code for design of highway reinforced concrete and prestressed concrete bridges and culverts(JTG D62—2004)of China, the prestress loss of bars is calculated. The effective prestress force, cracking load, decompression load and ultimate load are calculated. The calculation results agree well with the measured results. It provides the reference to evaluate the effective prestress force and ultimate load in the prestressed concrete beams.
Keywords:effective prestress force; cracking load; decompression load; ultimate load
作者简介：
陈勇，博士研究生。Email: cy_9923@126.com。
参考文献
［1］STEPHEN PESSIKI, MARK KACZINSKI，HERBERT H  WESCOTT. Evaluation of effective prestress force in 28-year-old prestressed concrete bridge beams［J］. PCI Journal, 1996, 41(6).
［2］房贞政. 预应力结构理论与应用［M］. 北京：中国建筑工业出版社，2005.