Flexural behavior of ultra-high performance concrete filled high-strength steel tube

To research the flexural performance of ultra-high performance concrete (UHPC) filled high-strength steel tube (UHPCFST) and UHPC filled double skin high-strength steel tube (UHPCFDST) under bending load, an experimental investigation was presented. In this paper, four UHPCFST specimens, one UHPCFDST with square tube inner specimen and three UHPCFDST with circular tube inner specimens were designed to evaluate the influence of steel ratio, steel yield strength, and cross-section combination form on the flexural performance of the specimens. Experimental results indicated that the composite action between UHPC and high-strength steel tube was efficient, all specimens showed ductile failure under pure bending load. As the steel ratio and steel yield strength increased, the ultimate flexural capacity of specimens significantly increased, but the changes of flexural stiffness were not obvious. The results also demonstrated that when the hollow section ratio was 0.535 to 0.567, the UHPCFDST with circular tube inner specimens had higher ultimate flexural capacity and ductility than the UHPCFST specimens. Compared with square inner tube, when the steel ratio was the same, circular inner tube was recommended for UHPCFDST specimens. An analytical model of ultimate flexural capacity for UHPCFST and UHPCFDST specimens was proposed. Compared with the three current codes, the accuracy of the model was proved.

Automated summary

This study investigated the flexural performance of UHPCFST and UHPCFDST under bending load and found that the composite action between UHPC and high-strength steel tube was efficient, resulting in ductile failure of all specimens. Increasing steel ratio and yield strength led to a significant increase in ultimate flexural capacity of specimens. Circular inner tube UHPCFDST specimens demonstrated higher ultimate flexural capacity and ductility compared to UHPCFST specimens within a certain hollow section ratio range.