Glass fiber reinforced polymer (GFRP) has been applied in hull structures for small and medium-size ships due its lightweight, high strength and easy fabrication. When the action load coming from the ship self-weight and the ocean environment becomes extremely large, the GFRP hull structure may present special failure modes and their evolution processes. How to define the ultimate strength study for GFRP hulls is a critical issue for vessel safety design. In this paper, one GFRP girder to represent the structural properties of the actual hull structure is selected as the research object. The GFRP girder is made of plates of varying thickness strengthened by hat stiffeners and foam. The hat stiffener, its attaching plate and core foam are made using an integral vacuum forming technique to avoid local construction defects. The sectional corners of the GFRP girder are provided with sufficient support by a combination of adhesive bonding and bolt secure connections. The failure experiment for the GFRP girder is performed on a four-point bending facility with a single hydraulic actuator to apply the bending moment. The strain variation is recorded by the digital image correlation (DIC) system on deck upper surface and 42 strain gauges on other critical regions. The deformation data is measured by 11 displacement sensors during a step-like increase of the applied load. The deformed shape are also recorded by the DIC system and the camera. Based on the experimental results, curves of the applied load and structural displacement are plotted to obtain the ultimate strength of the experiment girder. The failure modes and their evaluation processes are also discussed based on the video recordings. Finally, the failure process of the experiment GFRP girder is simulated using the nonlinear finite element method to study the effect of local delamination at various locations where the ultimate strength is determined. Both the experimental results and direct calculations demonstrate that the GFRP girder may exhibit a kind of brittle failure after the limit load point. The conclusions obtained in this paper will provide a guide for the design of GFRP ships and the modification of ship rules.

中文翻译：

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弯曲荷载作用下带帽型加劲肋和泡沫的 GFRP 梁结构破坏及极限强度试验研究

玻璃纤维增​​强聚合物（GFRP）因其轻质、高强、易于制造等优点，已应用于中小型船舶的船体结构。当船舶自重和海洋环境作用载荷变得极大时，GFRP船体结构可能会出现特殊的失效模式及其演化过程。如何定义GFRP船体的极限强度研究是船舶安全设计的关键问题。本文选取一根代表实际船体结构结构特性的GFRP梁作为研究对象。 GFRP 大梁由不同厚度的板材制成，并通过帽形加强筋和泡沫进行加固。帽形加强筋、其连接板和芯材泡沫采用整体真空成型技术制成，以避免局部施工缺陷。通过粘合剂粘合和螺栓紧固连接的组合，为 GFRP 梁的截面角提供足够的支撑。 GFRP 梁的破坏实验是在四点弯曲装置上进行的，该装置使用单个液压执行器来施加弯矩。应变变化由甲板上表面的数字图像相关（DIC）系统和其他关键区域的 42 个应变仪记录。变形数据由 11 个位移传感器在所施加的载荷阶梯式增加期间测量。 DIC 系统和相机也会记录变形的形状。根据试验结果，绘制外加载荷和结构位移曲线，以获得试验梁的极限强度。还根据视频记录讨论了故障模式及其评估过程。最后，利用非线性有限元方法对实验GFRP梁的破坏过程进行模拟，研究在极限强度确定的各个位置处局部分层的影响。实验结果和直接计算都表明，GFRP梁在达到极限荷载点后可能会出现一种脆性破坏。本文得出的结论将为GFRP船舶的设计和船舶规范的修改提供指导。