无粘结预应力CFRP筋钢纤维轻骨料混凝土梁受弯性能试验研究

建立无粘结预应力FRP筋张拉锚固体系,对8根以CFRP筋为非预应力筋的无粘结预应力CFRP筋轻骨料混凝土梁与1根普通混凝土对比试件进行两点对称加载,观察其破坏过程与破坏形态,分析了混凝土种类、预应力度和净跨长度对开裂弯矩、弯矩-跨中挠度曲线、裂缝宽度等受弯性能的影响.从等效轴向刚度思想出发,修正了现有的以钢筋为非预应力...

FLEXURAL BEHAVIOR OF STEEL FIBER-REINFORCED LIGHTWEIGHT AGGREGATE CONCRETE BEAMS PRESTRESSED WITH CARBON FIBER-REINFORCED POLYMER BARS

An unbonded prestressing anchorage system for carbon fiber-reinforced polymer (CFRP) tendons was introduced. Eight lightweight aggregate concrete (LWC) beams prestressed with unbonded CFRP tendons which used CFRP auxiliary reinforcements and one fabricated using normal weight concrete (NWC) were tested under a four-point bending condition. The influences of concrete type, of prestressed degree and, of clear span length on the cracking moment, on the moment-deflection response and, on the crack width were analyzed. The existing deflection and crack width models for unbonded FRP prestressed beams with steel auxiliary reinforcements were modified from the view of equivalent axial stiffness. The applicability of the modified models was evaluated based on the test results. It is shown that the serviceability limit state of the beams is mainly governed by the crack width limit. The ratios between the moment at crack width of 0.5 mm and the ultimate moment range from 41% to 52%. With the same total reinforcement amount, the increase in the prestressed degree helps delay the cracking of the specimens. Increasing the amount of the auxiliary reinforcement and of the unbonded prestressed tendons both improve the beam stiffness and restrain the propagation of the cracks. The modified Cheng’s and modified Meng’s deflection models provide accurate deflection predictions for LWC beams with unbonded prestressed and auxiliary CFRP reinforcements.