Sustained Load Deflection of High Strength Concrete Beams

高强混凝土梁的持续荷载挠度

• 批准号: 8614220
• 负责人: Arthur Nilson
• 金额: --
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1987
• 资助国家: 美国
• 起止时间: 1987-02-15 至 1989-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8614220&HistoricalAwards=false
• 关键词: Sustained; Load; Deflection; Strength; Concrete

Rapid growth interest in use of high strength concrete (compressive strength to about 12,000 psi) has caused concern that current design methods and codified procedures for design may not be appropriate. Many design equations found in the 1983 Building Code of the American Concrete Institute, governing most US practice, are based on tests of members using concrete strength not greater than 6000 psi. A nine-year program of research on high strength concrete at Cornell had three objectives: (a) to provide an understanding of the basic differences in behavior of the material, (b) to establish the engineering properties of the material, and (c) to study the behavior of reinforced concrete members made using the material. One of the more significant observations is that the creep coefficient for high strength concrete. Present Code procedures for design do not account for this. The point is of particular importance, because short- and long-term deflections may prove to be a governing aspect of design for slender members made using the material. This project is for further testing of beams under sustained loading, to study immediate and time-dependent deflections, crack growth, and internal force redistributions. Important variables include time, compressive strength, age at first loading, and the amount of tensile and compressive reinforcing steel. Results of the proposed research should help improve the implementation and increased use of high strength concrete in structures such as buildings and bridges.

人们对使用高强混凝土(抗压强度约为12,000磅/平方英寸)的兴趣迅速增长，这引起了人们的担忧，即目前的设计方法和编撰的设计程序可能不合适。在美国混凝土协会1983年的《建筑规范》中发现的许多设计公式，都是基于使用不超过6000磅/平方英寸混凝土强度的构件的测试。康奈尔大学一项为期九年的高强混凝土研究计划有三个目标：(A)了解这种材料的基本性能差异；(B)确定该材料的工程性能；(C)研究使用该材料制成的钢筋混凝土构件的性能。其中一个比较重要的观察结果是高强混凝土的徐变系数。目前的规范设计程序没有考虑到这一点。这一点特别重要，因为短期和长期的挠度可能被证明是使用这种材料制造的细长构件设计的主导方面。这个项目是为了进一步测试梁在持续荷载下的作用，以研究即时和随时间变化的挠度、裂纹扩展和内力重分布。重要的变量包括时间、抗压强度、首次加载时的龄期以及受拉和受压钢筋的数量。拟议研究的结果应有助于改进高强混凝土在建筑物和桥梁等结构中的实施和增加使用。