Reliability assessment of the EN 1992 restrained shrinkage crack model as applied to liquid retaining structures in South Africa.

Abstract

The South African design of liquid retaining structures (LRS) has traditionally involved the use of the British codes of practice, namely BS 8007:1987 and BS 8110-2:1985, due to South Africa not yet having developed its own equivalent code. BS 8007:1987 and BS 8110-2:1985 have since been replaced by EN 1992-3:2006 and EN 1992-1-1:2004 respectively. South African engineers are presented with the option of adopting the Eurocode 2 (EN 1992) design code for the design of LRS in place of the superseded corresponding British design codes; however, in the case of adoption, the issue of the code’s suitability for use under local conditions and thus its reliability requires investigation. Hence, an investigation into the reliability performance of the EN 1992 crack model as applied in the South African context will be undertaken. Cracking, a serviceability limit state, takes precedence over the effects of the ultimate limit state where the infringement of crack limits in liquid retaining structures may result in the loss of structural integrity. The First Order Reliability Method (FORM) of analysis was the probabilistic method of choice in this investigation. This research focussed on cracking due to restrained deformation with edge and end restraint conditions both being considered. The influence of significant parameters of the crack model was assessed in probabilistic terms. Model uncertainty and the restraint factor were both found to have borne the most influence on the reliability performance of the crack model. This research aimed to improve the reliability of the EN 1992 crack model for use in the South African context. This was achieved through attaining an understanding of the influence held by respective design variables on the crack model, thus bringing to light where within the crack models sensitivities lay. This then indicated the potentially most effective ways in which reliability compliance could be brought about in the case of code calibration. Future research must be conducted on the stochastic nature of the restraint factor and other basic variables. Research must also be conducted into the model uncertainty for crack formation.