Issue 29

L. Contrafatto et alii, Frattura ed Integrità Strutturale, 29 (2014) 196-208; DOI: 10.3221/IGF-ESIS.29.17 207 engineers engaged in structural analysis, are often not sufficiently equipped with advanced mechanical formulation or constitutive models. A critical capability of the designer is needed to understand the limit of the simulation. Furthermore the lack of experimental data concerning the minimum embedment length in the investigated materials implies that engineers apply the recommendation of the resin manufacturer, often oversized with respect to the real anchor depth. Therefore a database covering the main lithological types presents in each territorial area should be built. The numerical simulations developed in the paper illustrate how a bad modeling can produce really approximated results, eventually useful just in the estimation of limit value of the embedment depth separating the yielding of the steel bar from the localised fracture of the stone support. The results of these numerical test are indeed in agreement with the experimental evidence in term of ultimate strength only in the case of large embedment depth, in basalt and limestone, when the failure is depending on the yield stress of the rod. In that situations the elastic-plastic behaviour of the steel rod rules the problem and the numerical prediction is reliable. On the contrary, in the case of stone support with scarce mechanical properties or for very short embedment length the crisis arises with the development of a rupture cone, that remain perfectly bonded to the rod, for all its embedded length or only in the upper portion of it. The simulation of such mechanism is a difficult task, requiring specific tools and the opportune characterization of the constitutive laws ruling the behavior of the anchor constituents. Only following this way the correct prediction of the anchor strength and fracture phenomenon can be effectively pursued. R EFERENCES [1] Nilson, A. H., Internal Measurement of Bond Slip, ACI Structural Journal, 69 (1972) 439-441. [2] Cook, R. A., Behavior of chemically bonded anchors, Journal of Structural Engineering, 119 (1993) 2744-2762. [3] Cook, R. A., Konz, R. C., Factors Influencing Bond Strength of Adhesive Anchors, ACI Structural Journal, 98 (2001) 76-86. [4] Colak, A., Parametric study of factors affecting the pull-out strength of steel rods bonded into precast concrete panels, International Journal of Adhesion & Adhesives, 21 (2001) 487-493. [5] Bickel, T. S., Shaikh, A. Fattah, Shear Strength of Adhesive Anchors, PCI Journal, Sept-Oct (2002) 92-102. [6] Eligehausen, R., Cook, R. A., Appl, J., Behavior and Design of Adhesive Bonded Anchors, ACI Structural Journal, 103 (2006) 822-831. [7] Contrafatto, L., Cosenza, R., Experimental behaviour of post-installed adhesive anchors in natural stone, to appear, Construction and Building Materials, (2014). [8] Doerr, G. T., Cook, R. A., Klingner, R. E., Adhesive Anchors: Behaviour and Spacing Requirements, University of Texas, Austin, Research Report n. 1126-2 (1989) [9] McVay, M., Cook, R., Krishnamurthy, K., Pullout Simulation of Postinstalled Chemically Bonded Anchors, J. Struct. Eng., 122 (1996) 1016-1024. [10] Cook, R. A., Kunz, J., Fuchs, W., Konz, R. C., Behavior and Design of single adhesive anchors ander tensile load in uncracked concrete, ACI Structural Journal, 95 (1998) 9-26. [11] Cook, R. A., Doerr, G. T., Klingner, R. E., Bond stress model for design adhesive anchors, ACI Structural Journal, 90 (1993) 514-524. [12] Marti, P., Anchoring of Concrete Reinforcement Using HIT-HY 150, Hilti Development Corporation, Technical Report n. 93.327-1 (1993). [13] Eligehausen, R., Mallee, R., Rehm, G., Befestigungen mit Verbundankern (Fastenings with bonded anchors, Betomverk + FertigteilTechnik, 10 (1984) 686-692. [14] SAP2000, http://www.csi-italia.eu/software/sap2000 /, (2014). [15] PRO_SAP, http://www.2si.it /, (2014). [16] Straus7, http://www.enginsoft.it/software/straus/index.html , (2014). [17] Bazant, Z. P., Prat, P. C., Microplane model for brittle-plastic material. I: Theory. II: Verification., J. Engrg. Mech., 114(1988) 1672-1699 [18] Contrafatto, L., Cuomo, M., Di Venti, G.T., Finite elements with non homogeneous embedded discontinuities, European Congress on Computational Methods in Applied Sciences and Engineering, (2012) 9152-9171. [19] Contrafatto, L., Cuomo, M. , Fazio, F., An enriched finite element for crack opening and rebar slip in reinforced concrete members, International Journal of Fracture, 178 (2012) 33-50. [20] Cuomo, M., Contrafatto, L., Greco, L., A variational model based on isogeometric interpolation for the analysis of cracked bodies, International Journal of Engineering Science 80 (2014) 173–188.