Experimental pull-out tests and design indications for strength anchors installed in masonry walls
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ORIGINAL ARTICLE
Experimental pull-out tests and design indications for strength anchors installed in masonry walls Linda Giresini
. Mario Lucio Puppio . Francesca Taddei
Received: 14 January 2020 / Accepted: 14 July 2020 The Author(s) 2020
Abstract This study deals with the identification of the mechanical behavior of chemical anchors embedded in masonry walls. 108 pull-out tests are carried out in five types of masonry walls built with clay brick or vertically perforated units with cement mortar. Different parameters are taken into account: embedment depths, masonry type, anchor position (injection either in brick units or in mortar joints). The axial load capacity and the failure mode are observed for each test. The results are examined by means of elastic and plastic models assessing the efficiency of anchors installed in headers, stretchers or mortar joints. The anchors injected in mortar joints are shown to have much greater pull-out capacity than that found for anchors in bricks. Passing from 90 to 160 mm of embedment depth, a minimum increase by 40% of pull-out strength is observed. The most common failure modes are the sliding failure, which occurs for short anchors or weak masonry, and mixed
L. Giresini (&) M. L. Puppio Department of Energy Systems, Territory and Constructions Engineering, University of Pisa, Largo Lucio Lazzarino 1, 56100 Pisa, Italy e-mail: [email protected] M. L. Puppio e-mail: [email protected] F. Taddei Lehrstuhl fu¨r Baumechanik, Technical University of Munich, Munich, Germany e-mail: [email protected]
sliding/cone failure, for long anchors or strong masonry. An analytical model is proposed to design anchors in order to avoid or at least to limit brittle masonry failures and to identify the field of application of uniform stress models. Keywords Pull-out Chemical anchors Epoxy resin injection Masonry Pull-out capacity Embedment depth Sliding failure Abbreviations E f0 f0 EC6 fy Ger Gm h hc hef hmax K k P Pmax Ps rm
Steel young modulus Masonry compressive strength Masonry compressive strength as in EC6 Anchor tensile strength Shear modulus of the epoxy resin Shear modulus of masonry Embedment depth Cone depth Depth epoxy resin Maximum embedment depth Stiffness of the bond spring per unit length Stiffness of the bond springs per unit bond surface and unit slip Applied tensile force Pull-out strength Resistance of the threaded anchor Radius of the masonry cylinder
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rs ta ¼ ð/0 /Þ=2 gs ¼ Pmax =Ps k0
k ¼ Es As =Em Am kw R s0 s0EC6 s0m sc sm smax ss s(z) / /0 tmin t
Materials and Structures (2020)53:103
Radius of the steel bar Thickness of the adhesive layer Efficiency of the anchors Coefficient related to the characteristic of the resin and of the epoxy bar Relative axial stiffness of the steel bars versus the material support Slenderness ratio of the walls (height/thickness) Adherent perimeter Masonry shear stress Masonry shear strength as in EC6 Masonry shear stress from
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