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Deformed bar/wire anchors transfer a tensile load into concrete by a combination of bond between the anchor and the concrete and, in the case of hooked bars, bearing on the anchor hook. The concrete tensile breakout failure is one of the failure modes. This paper presents an analysis of the concrete tensile breakout failure mode for fully developed deformed bar/wire anchors and concludes that the concrete tensile breakout failure mode can govern over steel rupture failure mode in some cases.
Keywords: anchor; anchorage; bond; deformed bar/wire; finite element analysis (FEA); nuclear power plant; tensile breakout.
INTRODUCTION
Deformed bar anchors (DBAs) and deformed wire anchors (DWAs) have been used in precast concrete elements and cast-in-place concrete elements in nuclear power plants and many other facilities for many years. However, ACI 318-111 and ACI 318-142 do not define these types of anchors. In ACI 349-013 and ACI 349-13,4 a deformed bar/wire is defined as an anchor for a tensile load with a development length shown in Fig. RB.2.6(a) and Fig. RD.2.6(a), which is "the extent of the embedment within the jurisdiction of this code" as indicated in Section RB.2.6 and RD.2.6. Sections B2.2 and D.2.2 state that "reinforcement used as part of the embedment shall be designed in accordance with other parts of this code."
Referring to ACI 349-01/13 Appendix B.2.2/D.2.2 and Chapter 12 (other parts of this code) by the nuclear power plant design criteria, a straight or hooked DBA/ DWA connected to a steel plate is considered to be fully developed if it has a development length ld or ldh in accordance with Chapter 12 of ACI 349-01/13 as tensile reinforcement (assuming the minimum clear cover db and clear spacing 2db requirements are met, or no splitting failure). Hence, concrete tensile breakout design is not considered, and the tensile capacity of the anchors is based only on anchor steel tensile strength. In other words, DWAs/DBAs have been designed per Chapter 12 of ACI 349-01/13.
The majority of nuclear power plant facilities are concrete, and almost all structures, systems, and components (SSCs) and commodities are supported on embedment plates in concrete. Therefore, a significant amount of very dense, fully developed DBAs/DWAs, especially fully developed hooked DBAs/DWAs, are often used in seismic category I (equivalent to...