Fractureanalysisofquadruplefasteningswithbondedanchors

In order to investigate the failure mechanism and the failure load of quadruple fastenings with bonded anchors a series of numerical investigation was carried out. The studied specimens were bonded an- chors in a concrete block and subjected to tensile loading. In the calculations the microplane model with re- laxed kinematic constraint was used to simulate the concrete and bond materials. Totally more than 50 calcu- lations were performed. Varied were embedment depth (h. = 4d to 20d), spacings between anchors (s = 0.25h. 1 1 2 to 2.Sh.), anchor diameter (d = 8, 12 and 20 mm) and bond strength ( r,, = 6.2 to 22.5 N/111111). The results of 1 the numerical studies were compared with the results of experimental investigations. From these studies the failure mechanism of bonded group anchors is clearly revealed and the group effect on the failure load is clarified. Based on the numerical and experimental results a model for evaluating the failure load of quadru- ple fastenings with bonded anchors is proposed. 1 INSTRUCTION The studied specimens are bonded anchors of the injection type based on resin mortar anchored into a A bonded anchor consists of a reinforcing bar or a concrete block and subjected to tensile loading. The threaded rod inserted into a hole drilled in hardened considered anchor group is quadruple. A series of concrete which is filled with a bonding agent. Dur- experiments have been performed during the last ing the last 2 decades several research works on years (Lehr & Eligehausen, 1998). From the experi- bonded anchors have been published (Eligehausen, ments it is known that with variation of embedment Mallee & Rehm, 1984, 1997; Eligehausen, Lehr, depth and/or spacing among anchors the failure Meszaros & Fuchs, 1999; Cook, Doerr & Klingner, mode varies from concrete cone failure to pullout 1993; Cook, Kunz, Fuchs & Konz, 1998). The fail- failure.