端锚有粘结预应力纤维片材加固混凝土梁的受弯承载力

以现有的试验结果为基础,研究预张纤维片材在钢筋混凝土梁上的锚固方式及其加固梁的有效预应力取值。关于在片材两端进行机械锚固并沿其全长粘贴于梁底的纤维增强聚合材料与混凝土构成的复合截面,基于界面无滑移假定、平截面假定和材料应力—应变关系,分析了截面压区顶部混凝土纤维应变不同时对应的可能应变组合下的受弯极限状态。根据破坏时钢筋是否受拉屈服,分别给出了由片材拉断、混凝土压碎所引发的两大弯曲破坏类型的极限承载力表达式和界限破坏判别条件。通过分析19根矩形截面梁的试验数据及对这些试件进行的受弯承载力计算,得出承载力计算值与试验值之比的平均值为0.979,变异系数是0.064,说明承载力及破坏形态的计算值与试验结果吻合较好。只要考虑相应的材料参数,给出的公式还可用于预应力混合纤维片材加固的计算。

Flexural Strength of Reinforced Concrete Beams Pre-Stressed with End-Anchored and Length-Bonded FRP Laminates

On the basis of existing test results,the effective prestressing forces are discussed for reinforced concrete(RC) beams strengthened with pre-stressed fiber reinforced polymer(FRP) laminates along with the ways of anchoring the laminates.Based on the assumptions of non-slip on interface,plane section(remaining) and stress-strain relationships of materials,all possible strain combinations at ultimate limit state of flexure are analyzed for composite section of RC beam pre-stressed with end-anchored and(length-bonded) FRP.Various series of equations are presented to predict the corresponding ultimate(bending) moments according to whether the steel bars yield or not,and expressions are given to distinguish between two modes of flexural failure respectively due to fracture of FRP and crushing of concrete.A(series) of formulas are presented for calculation of the corresponding strengths,and their applicability is verified by comparison of the predicted results with the experimental ones(19 rectangular cross-section beams),which the mean value is 0.979,and variation coefficient of the ratio is 0.064.It shows that the calculation values of the bearing capacity and the failure configuration agree well with test results.And the presented expressions can be used for strengthened beams with pre-tensioned mixed fiber laminates using corresponding material properties.