自攻锚栓极限抗拉承载力计算方法

自攻锚栓是一类具有装卸方便快速、施工可调性好、临界边界距离短等优点的混凝土后锚固机械锚栓，近年来得到了越来越多的工程应用. 为保证自攻锚栓承载力符合要求及所锚固结构的安全性，需对其受拉时不同破坏模式对应的极限抗拉承载力进行严格的计算和设计. 目前国内外对自攻锚栓承载力方面的相关研究均较少，对其受拉破坏机理的研究更是缺乏，使设计者仅通过厂家提供个别设计值对锚栓承载力进行估算和设计，不能准确计算理论承载力值. 为了促进对自攻锚栓受拉拔破坏机理及其极限抗拉承载力计算的进一步研究，本文系统地总结了自攻锚栓在受外部静拉力荷载作用下锚栓拉断破坏、混凝土锥体破坏与组合破坏模式的形成机理，指出锚栓极限抗拉承载力及破坏模式与锚固深度的对应关系；详细介绍并分析了针对自攻锚栓各破坏模式的极限抗拉承载力预测模型；重点讨论了有关组合破坏模式极限抗拉承载力预测模型的研究现状，并展望了对其进一步验证及改进的必要性；最后描述了现有锚栓群组、间距、边距效应的计算方法，指出了对自攻锚栓在该领域研究的需求. 

Calculation Methods of Ultimate Tensile Strength for Screw Anchors

Screw anchors are a type of post-installed concrete anchors with the advantages of convenient and fast installation and removal, good construction adjustability, and short critical margin distance. Therefore, it has been used more in the field in recent years. To ensure that the requirements of bearing capacity of screw anchors and the safety of the anchored structure, the ultimate tensile strength corresponding to different tensile failure modes should be strictly calculated and designed. However, the research on the bearing capacity of screw anchors is relatively scarce, and that on its tensile failure mechanism is even less. Thus, the designers estimate and design the bearing capacity of screw anchors according to the individual design values provided by manufacturers, and cannot accurately calculate the theoretical ultimate strength. To further understand the tensile failure mechanism and calculation methods for the ultimate tensile strength of screw anchors, the formation mechanisms of the anchor bolt failure, concrete cone failure and combined failure mode for screw anchors under external static tensions are systematically summarized, and the relationship between the failure modes with the ultimate tensile strength and embedment depth is presented. The prediction model of the ultimate tensile strength corresponding to different failure modes is introduced and analyzed in detail. The state of the art on the prediction model of the ultimate tensile strength for the combined failure mode is discussed, and the prospect of further verification and improvement are explored. The current calculation methods of anchor group, spacing, and edge effects are presented, and it is also pointed out that there is a need for studying screw anchors in this regard.