Expansive concrete (EC) or steel fiber-reinforced expansive concrete (SF-EC) have been adopted for enhancing the performance of concrete-filled steel tube (CFST) columns, while the investigations on confinement mecha-nism and theoretical model for EC and SF-EC are limited. This study aims to develop a constitutive model for EC and SF-EC under tri-axial compression. In the first part, the results of tri-axial compression tests on 52 concrete cubes, were summarized and collected to form a database. In the second part, the failure criterions of concrete cubes, and performances of four existing stress-strain models were assessed and discussed using the database. The results of tri-axial compression with equal lateral confining stresses generally complied well with the compressive meridians of Ottosen failure criterion, whereas the Lode angles were around 56 degrees -58 degrees for the true tri-axial compression results. However, the existing models substantially underestimated the axial strains at peak stresses by at least 40, and thus the predicted stress-strain curves deviated considerably from the test results with much steeper initial ascending slopes. To this end, a modified constitutive model was proposed with Montoya et al.'s model as the base form and the key parameters updated as per the result database. The proposed model had good performances in predicting the peak axial stresses and the corresponding strains (average error at 8 and 19, respectively), as well as the full axial stress-strain curves.
展开▼
