Prediction model on compressive strength of recycled aggregate concrete filled steel tube columns

Abstract The design of composite members consisting of a tubular column and in-filled conventional concrete has been available and well-defined in the provisions. However, for steel tube members filled with recycled aggregate concrete, there aren't any other special requirements in the current provisions. In this study, the experimental test results are used to model and evaluate the ultimate strength of axially loaded recycled aggregate concrete filled steel tube columns. The test specimens has a length to diameter ratio ranging from 2.0 to 3.5, indicating that they are the stub column and not failing in overall buckling. The proposed model was derived based the technique of gene expression programming. The database utilized contains a total of 97 test results. The predictor variable employed to generate the model are outer diameter, thickness and yield strength of steel tube, length of the column, recycled coarse aggregate replacement ratio, and concrete compressive strength. The experimental data and associated analytical model are examined by four widely used design codes of ACI, Eurocode 4, AIJ, and DL/T. A sensitivity statistical analysis is further conducted to assess the contributions of each parameter affecting the axial capacity. The outcome indicates that the developed model gives reasonable predictions of the axial capacity of recycled aggregate concrete filled circular steel tube stub columns compared to the existing expressions.