Shrinkage Curvature of Cracked Reinforced Concrete Sections: Improving the Economy of Concrete Structures Through Good Science

开裂钢筋混凝土截面的收缩曲率：通过良好的科学提高混凝土结构的经济性

• 批准号: EP/C536649/1
• 负责人: John Forth
• 金额: $ 24.01万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FC536649%2F1
• 关键词: Shrinkage; Curvature; Cracked; Reinforced; Concrete

There are substantial commercial pressures driving the current trend in reinforced concrete multi-storey structures towards longer spans and thinner structural depths. The potential benefits of clear open spaces, the freedom of placing services and the reduction of building height (and the subsequent potential reduction in cladding costs) or conversely, the ability to incorporate an extra floor in the building (thus increasing rental potential) can have a significant effect on the overall economics of a scheme. However, these benefits cannot be fully exploited until it is possible to predict accurately the long-term deflection of concrete elements.A major problem in predicting the long-term deflection of cracked concrete flexural elements has always been the difficulty in isolating the deformation due to shrinkage from the effect of other parameters such as creep and tension stiffening. Current codes predict the long-term deflection of cracked concrete elements by using the approach developed for uncracked sections but incorporating cracked section properties. Whilst there is no question of the correctness of this in relation to uncracked sections, it has never been experimentally validated for cracked sections. Consequently, it may be extremely conservative and, therefore, have a restrictive influence on design strategy. The effect of shrinkage on a cracked section remains uncertain as it has not been possible to confirm the influence experimentally. The applicants now believe it is possible to overcome this difficulty and this application proposes an extremely innovative experimental approach which will allow the effect of shrinkage on the deformation of cracked members to be isolated for the first time. Recently, research by the applicants under a previous EPSRC funded project has resulted in a much better understanding of the tension stiffening phenomenon and, in particular, its decay with time. The effects of creep are already generally well understood. The results of the proposed research, and the data obtained by the Leeds and Durham concrete research team on tension stiffening, will finally allow designers to predict the long-term deflection of cracked concrete flexural elements with greater reliability.The current climate within the construction industry and the effect this has had on the cost and availability of steel is leading, and will continue to lead, to an increased use of concrete in construction (e.g. the major new Clarence Docks development in Leeds, where previously steel would have been chosen). The research is, therefore, very timely. It is now even more critical that this information is available to designers to ensure that maximum efficiency in the design and use of concrete is achieved so as not to restrict their competitiveness within the UK and EU construction industry.The proposed research will be performed at both the University of Leeds and the University of Durham. The experimental programme consists of two stages. The initial stage is concerned with confirmation of methodology. The second stage will isolate the effect of shrinkage using the innovative approach proposed by the investigators, contributing to an improved design method and more accurate assessment of shrinkage. The proposal has 6 industrial collaborators providing in-kind and cash contributions totalling 33,460. The total amount of funding being sought by the two universities is 274,537.

巨大的商业压力推动了当前钢筋混凝土多层结构向更长跨度和更薄结构深度发展的趋势。清晰的开放空间、放置服务的自由度和建筑高度的降低（以及随后可能降低的包层成本）的潜在好处，或者相反，在建筑物中增加额外楼层的能力（从而增加租金潜力）可以具有对计划的整体经济性产生重大影响。然而，只有能够准确预测混凝土构件的长期挠度，才能充分利用这些优势。预测开裂混凝土弯曲构件的长期挠度的一个主要问题始终是难以隔离变形，因为其他参数（例如蠕变和拉伸刚度）影响的收缩。现行规范通过使用为未开裂截面开发但结合了开裂截面特性的方法来预测开裂混凝土构件的长期挠度。虽然对于未破裂的部分而言，这一点的正确性是毫无疑问的，但它从未针对破裂的部分进行过实验验证。因此，它可能非常保守，从而对设计策略产生限制性影响。收缩对裂纹部分的影响仍然不确定，因为无法通过实验证实这种影响。申请人现在相信可以克服这个困难，并且本申请提出了一种极其创新的实验方法，该方法将首次允许分离收缩对裂纹构件变形的影响。最近，申请人在之前 EPSRC 资助的项目下进行的研究使人们对张力硬化现象，特别是其随时间的衰减有了更好的理解。蠕变的影响已经广为人知。拟议研究的结果以及利兹和达勒姆混凝土研究团队获得的有关拉伸硬化的数据最终将使设计师能够更可靠地预测开裂混凝土弯曲元件的长期偏转。当前建筑行业的气候这对钢材的成本和可用性产生的影响正在并将继续导致建筑中混凝土的使用增加（例如利兹的克拉伦斯码头新开发项目，以前会选择钢材）。因此，这项研究非常及时。现在更重要的是，设计师必须能够获得这些信息，以确保在混凝土的设计和使用中实现最大效率，以免限制他们在英国和欧盟建筑行业的竞争力。拟议的研究将在两个国家进行利兹大学和杜伦大学。实验计划分为两个阶段。初始阶段涉及方法的确认。第二阶段将使用研究人员提出的创新方法来隔离收缩的影响，从而有助于改进设计方法和更准确地评估收缩。该提案有 6 个行业合作者提供了总计 33,460 美元的实物和现金捐助。两所大学寻求的资金总额为274,537。

项目成果

Modelling shrinkage of early age concrete due to drying diffusion

模拟早期混凝土因干燥扩散而产生的收缩

• 发表时间: 2009
• 期刊: magazine of Concrete research
• 影响因子: 2.7
• 作者: R Mu

Test Rig for Shrinkage Curvatures of Cracked Reinforced Concrete Beams

开裂钢筋混凝土梁收缩曲率试验台

• DOI: http://dx.10.1111/j.1475-1305.2009.00654.x
• 发表时间: 2011
• 期刊: Strain
• 影响因子: 2.1
• 作者: Scott R

Modelling of shrinkage induced curvature of

收缩引起的曲率建模

• 发表时间: 2008
• 作者: R Mu

Verification of cracked section shrinkage curvature models

裂纹截面收缩曲率模型验证

• DOI: http://dx.10.1680/stbu.12.00046
• 发表时间: 2014
• 期刊: Proceedings of the Institution of Civil Engineers - Structures and Buildings
• 作者: Forth J

Moisture loss induced shrinkage of concrete

水分流失导致混凝土收缩

• 发表时间: 2008
• 作者: R Mu