159 / 2022-04-29 23:39:36

Prediction model on creep of high strength self-compacting concrete filled steel tube

High strength self-compacting concrete-filled steel tube,Creep,Concrete model,Axial compression

High strength self-compacting concrete-filled steel tube (HS-SCCFST) is a relatively new structure member that combines special engineered properties in the fresh state of high strength self-compacting concrete with a series of advantages of concrete-filled steel tube, such as good seismic and fire performance. Based on these positive characteristics, there is great potential for using HS-SCCFST by engineers and contractors in civil engineering. Considering that high strength self-compacting concrete (HS-SCC) generally has a lower water-binder ratio, higher paste volumn and addition of mineral admixture, it is expected to show different shrinkage and creep compared to normal vibrated concrete. Existing concrete models for HS-SCC only consider the influence of the low water-binder ratio and high paste volumn on the creep of concrete, without considering the effect of the addition of supplementary cementitious materials such as fly ash, silica fume and slag. A new creep prediction model based on the comprehensive analysis on the available models of both ordinary concrete and self-compacting concrete are proposed for HS-SCC and HS-SCCFST, which accounts for the influence of supplementary cementitious materials on the development of basic creep and on the final value of basic creep of HS-SCC. In order to verify the reliability of the proposed model in predicting the long-term responses of HS-SCCFST, the creep models were benchmarked against the long-term tests on six loaded axially HS-SCCFST columns. The mass ratio between SCM and cement of HS-SCC core in the experiments were in the range of 9-35%. When predicting the test results, the step-by-step procedure was employed by adopting an infinite notional size for the concrete component to eliminate the effects of relative humidity. It is indicated that the modified model proposed in this paper has the best performance in estimating the basic creep of HS-SCC members that contents SCMs and also has the best accuracy in predicting the creep of HS-SCCFST with the maximum deviation within 20%, which can be applied in the analysis of long-term responses for such member in the practical engineering.