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机构地区:[1]湖南大学
出 处:《土木工程学报》2007年第2期18-24,共7页China Civil Engineering Journal
基 金:国家自然科学基金(50478052);教育部优秀青年教师资助计划项目(教人司(2002)350号);湖南省科技计划项目(06SK3100)
摘 要:碳纤维(CFRP)筋具有优异的物理力学性能,可用于替代传统的预应力钢筋。制作了体外配置碳纤维筋预应力混凝土箱梁模型,对持续均布荷载作用箱梁的截面应力重分布、长期挠曲变形及裂缝发展等规律进行了1001 d的试验观测。基于素混凝土柱体的实测徐变系数,运用双线性法和曲率法分别对试验箱梁的长期挠曲变形进行预测。试验结果表明:受压钢筋应变较初值增长225%~268%,受拉钢筋的应变较初值增长36.2~38.6%,混凝土表面压应变较初值增长164%~224%。按现行设计规范计算长期荷载作用特征裂缝宽度较实测值偏小11.8%~55.5%。跨中长期挠曲变形实测值为初始变形的2.32~2.42倍,较现行设计规范取值偏大18.5%。Carbon fiber reinforced polymer (CFRP) tendons, due to excellent physical and mechanical performance, may be employed to replace conventional prestressed steel bars. A concrete box girder model prestressed with externally CFRP tendons was cast, and the stress redistribution, deflection and crack development of the girder model were tested for 1001d under sustained uniform load. Based on the creep coefficient of plain concrete columns, the long-term deflection of the box girder was predicted applying both the bilinear method and the curvature method. The test results indicated that the strain of the compressive bars would be increased by 225%-268%, the strain of the tensile bars increased by 36.2-38.6%, and the surface strain of the compressive concrete increased by 164%-224%, as compared with the initial values, respectively. The long-term characteristic crack width calculated by using the present design code would be 11.8%-55.5% less than the test value. The long-term deflection at mid-span in the test would be 2.32-2.42 times of the initial value, and the deflection in the test is 18.5% larger than that adopted by the present design code.
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