Creep behaviour of tension loaded adhesive anchors in non-cracked low strength concrete

Post-installed anchorages or reinforcements using bonding adhesives are invariably used in the present day construction industry. Although, various attempts to develop a generalized theory for design and analyses of adhesive anchorages have been made, the actual anchorage behaviour is still considered to be dependent on the adhesive product in use. The creep behaviour of adhesive anchors were investigated again intensively after several failure were observed. Several research experiments in this regard are performed by different researchers to establish a new procedure of failure accounting the creep effects of adhesive anchors. This work discusses the results of an experimental program undertaken at the University of Stuttgart, for establishing the time-to-failure behaviour under sustained loads for two different adhesive anchor products. The complete test program included reference pull out tests to evaluate the ultimate capacities. Sustained load tests were performed for the load levels corresponding to 85%, 75% 65% and 55% of the ultimate capacity observed in the reference tests. The test program also included sustained loading tests at different temperature conditions like ambient temperature (23°C) and moderately high temperature (43°C). A comparison of the creep behaviour for standard and sub-standard installation condition was also included in the test program to see the effect of a reduced installation cleaning process. In this paper, the results for standard installation with ambient temperature of 23°C are used to demonstrate the sustained load effects in the framework of time-to-failure behaviour. The possibility of arriving at a safe load level which can be sustained throughout the design lifetime of 50 years is discussed using the time-to-failure curves.