Although square twisted section reinforcement is no longer used in new construction, there remain many older structures still in service that were built with such bars. The increasing need for assessment of existing construction means there remains a continuing need for information on performance over older types of reinforcement. Research into plain surface bars essentially ceased when ribbed bars became the norm, and plain bars have consequently been bypassed in developments in understanding of bond since 1960. The basis through which margins of safety are introduced for design has also changed as formal methods for analysis of reliability have developed. An analysis of test data on bond of square twisted bars, also termed Type 1 deformed or Ransome type bars is presented, and a new semi-empirical formulation for anchorage capacity of straight square twisted bars in R.C. structures consistent with the reliability-based approach included in the forthcoming second generation of Eurocodes is derived. The expression parallels that for ribbed bars in the fib Model Code 2010. A comparison with provisions of some historical international design codes suggests that in some cases the margin of safety against failure of straight plain bar anchorages may have been lower than would be required by current norms. Implications for practice are briefly discussed.

中文翻译：

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用于评估现有结构的方形扭曲钢筋的锚固和搭接能力

尽管新建筑中不再使用方形扭曲截面钢筋，但仍有许多使用此类钢筋建造的旧结构仍在使用中。对现有建筑评估的需求日益增加，这意味着仍然需要有关旧类型钢筋的性能信息。当带肋钢筋成为规范时，对平面钢筋的研究基本上停止了，因此自 1960 年以来，在理解结合的发展中，平面钢筋已被绕过。引入设计的安全边际的基础也随着分析钢筋的正式方法而改变。可靠性已经发展。对方形扭曲钢筋（也称为 1 型变形钢筋或 Ransome 型钢筋）粘结的测试数据进行了分析，并且推导出了一种新的半经验公式，用于 RC 结构中直方扭曲钢筋的锚固能力，与即将到来的第二代欧洲规范中包含的基于可靠性的方法一致。该表述与 fib 模型规范 2010 中的肋条钢筋相似。与一些历史悠久的国际设计规范的规定进行比较表明，在某些情况下，直条钢筋锚固失效的安全边际可能低于当前要求的安全边际。规范。对实践的影响进行了简要讨论。与一些历史悠久的国际设计规范的规定进行比较表明，在某些情况下，防止直条锚固失效的安全边际可能低于现行规范所要求的。对实践的影响进行了简要讨论。与一些历史悠久的国际设计规范的规定进行比较表明，在某些情况下，防止直条锚固失效的安全边际可能低于现行规范所要求的。对实践的影响进行了简要讨论。