Studies on U-wraps generally focus on the experimental results and mechanisms of the shear strengthening effect. Only a few studies have focused on the anchoring effect of the longitudinal FRP due to addition of the U-wrap. Lee and Lopez (Constr Build Mater 194:226–237, 2016) have found experimentally from pull-out tests that incremental changes occur in the debonding strain at the concrete-FRP interface depending on the various type of U-wraps. The proposed numerical method using the Frictional Bond-Slip (FBS) model has been validated by comparing the pull-out test results (Lee and Lopez Constr Build Mater 194:226–237, 2016). In the present study, the FBS model was applied to charactgerize the behavior of a large scale FRP strengthened T-beam with multiple U-wraps. First, the 2-dimensional (2D) model for pull-out test was developed. Debonding load and behavior of the model were compared with both the experimental results (Lee and Lopez Constr Build Mater 194:226–237, 2016) and simulation results of a 3-dimensional (3D) model from a previous study (Lee and Lopez Constr Build Mater 194:226–237, 2016). Next, the 2D model was applied to model the behavior of a large scale FRP strengthened T-beam with multiple U-wraps. The conducted 2D simulation using the proposed FBS model predicted well the strains at various locations on the FRP sheet, the flexural capacity and complex failure mode of the FRP strengthened beam with several U-wraps. The proposed FBS model was also applied to other comparable studies, and debonding strains were successfully predicted within an error margin of 7%. Using the validated model, a parametric study of FRP strengthened T-beam was conducted with various key parameters of U-wrap, such as the angle of U-wrap and the number of U-wrap.

中文翻译：

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摩擦黏结滑移模型在带 U 型包裹的大型 FRP 加固 T 梁中的应用

对 U 形缠绕件的研究一般集中在剪切强化效应的实验结果和机制上。只有少数研究关注由于添加 U 形包裹而导致的纵向 FRP 的锚固效果。Lee 和 Lopez（Constr Build Mater 194:226–237, 2016）通过拉拔试验发现，混凝土-FRP 界面处的脱粘应变发生增量变化，具体取决于各种类型的 U 形包裹。通过比较拉拔测试结果（Lee 和 Lopez Constr Build Mater 194:226–237, 2016）验证了所提出的使用摩擦粘合滑移 (FBS) 模型的数值方法。在本研究中，FBS 模型被应用于表征具有多个 U 形包裹的大型 FRP 加固 T 梁的行为。首先，开发了用于拉拔测试的二维 (2D) 模型。将模型的剥离载荷和行为与实验结果 (Lee and Lopez Constr Build Mater 194:226–237, 2016) 和先前研究 (Lee and Lopez Constr建造材料 194:226–237, 2016)。接下来，应用二维模型来模拟具有多个 U 形包裹的大型 FRP 加固 T 梁的行为。使用所提出的 FBS 模型进行的 2D 模拟很好地预测了 FRP 片材上不同位置的应变、弯曲能力和具有多个 U 形缠绕的 FRP 加强梁的复杂失效模式。所提出的 FBS 模型也应用于其他类似的研究，并且在 7% 的误​​差范围内成功预测了脱粘应变。使用经过验证的模型，