Strengthening of Infill Masonry Walls with Fiber Reinforced Polymer (FRP) Composites

世界范围内的工程界已经确定，在地震事件中，无筋砌体（URM）墙体的失效是造成物质损失和人员伤亡的主要原因之一。开发有效和经济的砌体构件改造技术是迫切需要的。纤维增强聚合物（FRP）复合材料可能为受大风或地震引起的面内和面外荷载的URM墙的加固提供了有吸引力的解决方案。钢筋混凝土（RC）或钢框架与填充URM墙是常见的施工实践。填充墙与结构框架的相互作用往往被忽视，以简化设计。忽略填充墙的作用并不一定意味着保守的设计。填充墙可以极大地增强柔性框架的刚度，并显著影响建筑不同结构构件的水平荷载分布。现有墙体的加固必须考虑到这种行为。拟建项目将重点研究FRP筋和层压板加固砌体墙的抗剪性能。前者是一种名为FRP结构重定向的新技术。玻璃钢结构改造是指在砌体床缝内插入玻璃钢。FRP筋既可以嵌入环氧基浆料中，也可以嵌入胶凝浆料中。用该方法加固砌体的初步试验取得了良好的效果。除了增加面内墙体容量外，结构重新定位比FRP层压板更具侵入性，因为保留了砌体美学。两组墙体将被测试。第一个系列，A系列，将评估用FRP复合材料加固的URM墙的剪切性能，以确定结构性能方面最有效的加固方案。属于A系列的墙壁将用混凝土砌体单元（CMU）建造。试件将在面内循环荷载下进行试验。试验装置配置将确保剪切破坏的发生。在A系列中测试的最有效的加固方案将被选择用于b系列填充墙的加固。该系列将研究填充墙的剪切行为及其与周围结构RC框架的相互作用。填充墙将被钢筋混凝土框架包围，并在面内循环荷载下进行测试。面内加载破坏后，将试件移至振动台，在振动台上进行面外加速度，观察墙体的面外稳定性。将开发分析和数值模型来验证和理解使用复杂和简单理想化的实验结果。分析结果将用于实施设计方案的剪切加强URM填充墙供从业人员使用。该项目将成为开发经济有效的现有填充墙改造技术的里程碑。在资金和时间的限制下，它将整合实验、分析和设计三个阶段，为科学家和专业人士提供一种非常有前途的新技术的优势和特点的清晰快照。

The worldwide engineering community has identified failures of unreinforced masonry (URM) walls as one of the major causes of material damage and loss of human life during seismic events. The development of effective and affordable retrofitting techniques for masonry members is an urgent need. Fiber Reinforced Polymer (FRP) composites may provide attractive solutions for the strengthening of URM walls subjected to in-plane and out-of-plane loads resulting from high winds or earthquakes. Reinforced concrete (RC) or steel frames with infill URM walls are a common construction practice. Interaction of infill walls with the structural frame has often been neglected to simplify the design. Ignoring the contribution of the infill wall does not necessarily indicate a conservative design. Infill walls can greatly stiffen a flexible frame and significantly affect the horizontal load distribution to different structural members of the building. Strengthening of existing walls must account for this behavior.The proposed project will focus on the study of the shear behavior of infill masonry walls strengthened with FRP bars and laminates. The former is a novel technique denominated FRP structural repointing. FRP structural repointing consists of inserting FRP bars into the masonry bed joints. The FRP bars can be embedded either in an epoxy-based paste or a cementitious paste. Preliminary tests on masonry specimens strengthened by this technique have shown promising results. In addition to increasing in-plane wall capacity, structural repointing is less intrusive than FRP laminates because the masonry aesthetics are preserved. Two series of walls will be tested. The first series, Series A, will assess the shear behavior of URM walls strengthened with FRP composites to determine the most efficient strengthening schemes in terms of structural performance. The walls belonging to Series A will be constructed with concrete masonry units (CMU). The specimens will be tested under in-plane cyclic loading. The test setup configuration will ensure the occurrence of shear failure. The most efficient strengthening schemes tested in Series A will be selected for the strengthening of the infill walls in Series B. This series will investigate the shear behavior of infill walls and their interaction with the surrounding structural RC frame. The infill walls will be surrounded by a RC frame and tested under in-plane cyclic loading. After failure due to in-plane loading, the specimen will be moved to a shake table where it will be subjected to out-of-plane acceleration to observe the out-of-plane stability of the wall. Analytical and numerical models will be developed to verify and understand the experimental findings using both complex and simple idealizations. The analytical results will be used to implement design protocols for the shear strengthening of URM infill walls to be used by practitioners.This project will represent a milestone in the development of affordable and effective retrofitting techniques for existing infill walls. Within the constraints of funding and time, it will integrate the three phases of experimentation, analysis, and design to provide scientists and professionals with a clear snapshot of the advantages and characteristics of a highly promising new technology.