Lifetime Extension of Reinforced Concrete Slab-on-Beam Structures

就经济繁荣和更可持续的未来而言，延长现有公路的使用寿命和建设钢筋混凝土基础设施是当务之急。在较长时期内减少干扰和分摊建筑所包含的能源和环境影响的能力将导致能源和资源消耗方面直接、有形和显著的节省。由于建筑业通常占英国GDP的10%，而英国一半的建筑活动与翻新和维修有关，很明显，在建筑领域实施有效的技术创新有很大的空间。在英国，一个主要的挑战是，不仅我们的基础设施的平均年龄在增加，而且负载要求也越来越高。因此，由于老化、用途变化和/或强度不足而需要干预的国家建筑数量正在增加。对于钢筋混凝土（RC）结构，纤维增强聚合物（FRP）材料已被用作额外的增强材料，以增加或恢复强度能力。这些材料具有高强度重量比，耐用，易于安装。到目前为止，碳FRP树脂粘结强化系统是最常见的。frp增强应用的市场份额已经导致整个行业的使用激增，并且确实在逐年增长。然而，我们认识的发展并没有跟上应用的增长。当我们考虑到典型的大型桥梁或建筑结构和实际加固配置时，我们的知识有很大的差距。由于可及性问题、剪切破坏的脆性和复杂的力学行为，RC结构的剪切加强是一个特别的挑战。最初的设计指导在建立FRP系统使用的基础方面发挥了重要作用，但该指导必须借鉴具体研究的结果，这些研究通常只包括可能的参数和相互作用的子集，例如小型矩形梁。然而，有越来越多的证据表明，在现有的指导中没有捕捉到基本剪切行为的许多方面。最近的研究强调了FRP加固大型结构和复杂几何结构的预测和观察行为之间的明显矛盾。特别是，剑桥大学和巴斯大学的工作表明，在t梁中，被认为是板对梁结构的代表，目前的指导可能是不保守的，但对于大型矩形梁，过于保守。这些矛盾带来了困难，因为大型梁上板结构构成了我们周围基础设施的很大一部分，并且代表了使用FRP加固以延长使用寿命的目标区域。在目前的项目中，将进行全面的实验和分析方案，以了解使用粘合碳FRP织物系统在剪切中加强梁的基本力学。尺寸的影响将通过考虑从“实验室”尺度到实践中发现的实际尺寸结构的尺度范围的加强t梁来研究。这些有针对性的研究将导致改进的设计方法，这些方法反映了对破坏机制和依赖于结构几何形状和尺寸的相互作用的全面理解。通过提供实用、安全和持久的技术进步，使现有钢筋混凝土结构得以升级，以满足二十一世纪的需求，这些成果将产生重大而及时的影响。

The lifetime extension of existing highway and building reinforced concrete infrastructure is a priority in terms of economic prosperity and a more sustainable future. The ability to reduce disruption, and amortise the embodied energy and the environmental impact of construction over an extended period will lead to direct, tangible and significant savings in energy and resource consumption. As construction typically accounts for up to 10% of the UK's GDP, and half of UK construction activity is associated with refurbishment and repair, it is clear that there is substantial scope to implement efficient technological innovations in the construction sector. In the UK, a major challenge is that, not only is the average age of our infrastructure increasing, but also the loading requirements are becoming more demanding. So the national pool of structures requiring intervention due to deterioration, changes of use, and/or a lack of strength is growing. For reinforced concrete (RC) structures, fibre-reinforced polymer (FRP) materials have been used as additional reinforcement to increase, or reinstate, strength capacity. These materials have a high strength-weight ratio, are durable and easy to install. To date, carbon FRP resin bonded strengthening systems have been the most common. The market share of FRP-strengthening applications has resulted in a proliferation of usage across the industry, and indeed continues to grow year on year. However, the development of our understanding has not kept pace with the growth in applications. There are significant gaps in our knowledge when typical large bridge or building structures and practical strengthening configurations are considered. The shear strengthening of RC structures is a particular challenge due to accessibility issues, the brittle nature of shear failures and the complex mechanics of the behaviour. Initial design guidance has played an important role in establishing the basis for the use of FRP systems but this guidance has necessarily drawn upon the results of specific studies which often only encompass a subset of possible parameters and interactions e.g. small-scale rectangular beams. However, there is an increasing body of evidence that suggests that a number of aspects of the fundamental shear behaviour are not captured in existing guidance. Recent studies have highlighted apparent contradictions between the predicted and observed behaviour of FRP strengthened large scale structures and structures with complex geometries. In particular, work at Cambridge University and Bath University have shown that in T-beams, which are considered representative of slab-on-beam structures, the current guidance can be unconservative yet for large scale rectangular beams, overly conservative. These contradictions pose difficulties since large-scale, slab-on-beam structures constitute a large proportion of the infrastructure that surrounds us and represents a target area for the use of FRP strengthening for lifetime extension. In the current project, a comprehensive experimental and analytical programme will be undertaken to understand the fundamental mechanics of beams strengthened in shear using bonded carbon FRP fabric systems. The effect of size will be investigated by considering strengthened T-beams with scales ranging from 'laboratory' scales to realistically sized structures found in practice. These targeted studies will lead to improved design approaches which reflect a comprehensive understanding of the failure mechanisms and the interactions that depend on the geometry and size of the structure. The deliverables will have a significant and timely impact through the provision of practical, safe and durable technological advances to enable the upgrading of existing RC structures to meet the demands of the 21st century.