摘要
在简支变连续法加固的连续梁桥中,负弯矩区承担的活荷载作用相对较大,截面易发生疲劳破坏。以钢纤维自应力混凝土作为叠合层,研究负弯矩作用下叠合梁的疲劳性能。为模拟负弯矩疲劳作用,对7根倒置的T形截面叠合梁施加等幅疲劳荷载,并分别取0.55,0.65,0.70和0.75倍静力极限荷载作为疲劳荷载上限。试验过程中发现,叠合梁的破坏均为叠合层内钢筋疲劳破坏所致,而叠合面则表现有良好的抗疲劳性能。以试验数据为基础,阐明了钢纤维自应力混凝土对裂缝宽度和刚度损失的限制机理,分析了不同疲劳应力比情况下钢筋应力幅、裂缝宽度、刚度损失等与疲劳循环的关系,建立了叠合层内钢筋的S-N疲劳方程。试验结果表明,钢纤维自应力混凝土对叠合梁的裂缝宽度和刚度损失有较强的限制作用,疲劳循环达200万次时,能够满足结构的耐久性能和正常使用性能要求。
In concrete bridges strengthened by transforming from simply-supported to continuous beams, live load undertaken by the negative moment area is relatively larger and the relevant cross sections are often prone to fatigue failure. Composite layer with steel fiber reinforced self-stressing concrete and fatigue property of composite beams under negative moment are studied. To simulate negative moment fatigue action, fatigue load of constant amplitude is applied on 7 inverted T-section composite beams, and 0.55, 0.65, 0.70 and 0.75 times of the static limit load are used as the upper limit fatigue load. The steel bars in composite layers failed and caused failure of the composite beams, with satisfactory fatigue performance from the bonding interface. The mechanisms for cracks limited by steel fiber reinforced self-stressing concrete and the stiffness loss are determined, and the relationships of steel bar stress amplitudes, under different fatigue stress ratios, with crack width, stiffness loss and fatigue cycle are analyzed, to establish S-N fatigue equation for steel bars in composite layers. Test result shows that steel fiber reinforced self-stressing concrete may significantly restrain the crack width and the stiffness loss of composite beams, and that the requirement of structure durability and normal use can be satisfied with 2 million of fatigue cycles.
出处
《土木工程学报》
EI
CSCD
北大核心
2009年第11期23-30,共8页
China Civil Engineering Journal
基金
辽宁省交通厅科研重点项目(200514)
关键词
钢纤维
自应力混凝土
叠合梁
负弯矩
疲劳
steel fiber
self-stressing concrete
composite beam
negative moment
fatigue
