Anchor Head Models : Classification, Adaptability & Design-Paper

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The paper classifies commonly used anchor heads for tieback systems and discusses how to select them according to the retaining structure, anchor load, and required inclination. Anchor heads transfer loads from the wall to the reinforcing bar or tendon.<br /><br />Reinforcement may consist of bars or strand tendons. Bars are generally less costly for service loads up to 400 kN, while strands provide greater strength per cross-sectional area and are typically more economical above that level. The reinforcement choice influences the required robustness of the anchor head.<br /><br />Six punctual anchor-head models are described: distribution plates, optionally combined with a concrete base, beam, or wall opening (Model 1); a biased wedge (Model 2); a robust steel bracket (Model 3); a scabbard (Model 4); a folded steel clamp (Model 5); and a trapezoidal plate for secant-pile walls (Model 6). Their suitability varies by wall type and design constraints. Some models accommodate inclined anchors; lighter options are generally intended for low loads, while steel brackets and scabbards suit more demanding applications.<br /><br />A finite-element study examines Model 3, checking steel-plate stresses against a 235 MPa elastic limit. The rectangular repartition plate is the most highly stressed, owing to bending and stress concentration around its opening. Triangular plates are mainly in compression, while their punching stresses affect the required thickness of the distribution plate. Increasing triangular-plate thickness can reduce the distribution plate’s thickness requirement. For ULS loads below 400 kN, anchor inclination has little influence on plate thickness.<br /><br />The authors present the classification as an initial practical guide. Further parametric studies could help designers optimize steel use, cost, and on-site handling, particularly for highly loaded anchors.

Keywords

tieback systems

anchor heads

reinforcement bars

strand tendons

retaining structures

anchor load

inclined anchors

distribution plates

steel bracket

finite element study