Translation of the reviewed German paper published in 5. Jahrestagung des DAfStb in Kaiserslautern, September 2017 - 1 - Design of Anchor Fastenings with Elastic Base Plates Subjected to Tension and Bending Longfei Li 1) 1 Dr. Li Anchor Profi GmbH Abstract For the design of anchor fastenings with base plates under the combined loadings of tension and bending, FprEN 1992-4 (EC2, part 4) [1] dictates that the anchor tension forces are distributed in a linear fashion assuming that the base plate remains flat. To fulfill this condition, the base plate must be sufficiently stiff or rigid so that relative deformation caused by bending is negligibly small. The condition for a rigid base plate has been studied and discussed for decades without a satisfactory solution. The latest investigations show that the required thickness for the rigid base plate can be so great in many application cases that it cannot be used in practice. This is confirmed by Schneider's statements of 1999 and 2014 [10, 11] that the assumption of rigid base plates seems to be useless for the calculation of anchor tension forces for plates with normal thicknesses. That means, for base plates of normal thicknesses, the bending deformations of the base plate must be considered in the design and an elastic base plate model must be used in practice. In this paper, the regulations in FprEN 1992-4 for the calculation of anchor tension force are analyzed. The special features for the design of anchor fastenings with elastic base plates are explained and discussed by calculation examples using a third-party anchor design software for headed studs and post-installed anchors [2]. Keywords: Base plate stiffness, beam theory, rigid base plate, elastic base plate 1. Introduction The derivation of action loads in anchors is generally regulated by section 6.1 of FprEN 1992-4 [1] as follows: 6.1 (2) The actions acting on a base plate shall be transferred to the anchors as statically equivalent tension and shear forces. 6.1 (4) … prying effects shall be explicitly considered in the design of the anchor (see Figure 1.1). Prying forces Cpr arise with deformation of the base plate and displacement of the anchors. 6.1 (5) In general, elastic analysis may be used for establishing the loads on individual anchors both at ultimate and serviceability limit states. Section 6.2.1 of FprEN 1992-4 [1], however, allows the calculation of the anchor tension forces as if it follows the “beam theory” (Fig. 1.2), or analogous to Bernoulli's hypothesis assuming a linear distribution along the base plate and a linear stress- strain relationship assuming the base plate is sufficiently stiff. The condition of sufficient base plate rigidity is defined by FprEN 1992-4 in 6.2.1 (2) as follows: a) the base plate remains elastic under design actions (σEd ≤ σRd) and b) its deformation remains negligible in comparison with the axial displacement of the fasteners. If this requirement for the deformation is not fulfilled, the elastic deformation behavior of the base plate has to be taken into account to determine the design value of tension forces acting on each fastener. From the above-mentioned regulations, the following questions arise: 1) How accurate must the calculation model or calculation assumption be, with which the calculated anchor tension forces can be treated as equivalent in comparison to the real anchor tension forces in base plates according to section 6.1 (2) of FprEN 1992-4 [1]? 2) How can the prying effects be considered in the anchor design? 3) Does the beam theory in section 6.2.1 of [1] correspond to the prescribed elastic analysis of section 6.1?
Design of Anchor Fastenings with Elastic Base Plates Subjected to Tension and Bending
Jun 20, 2023
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