Study on Axial Compression Performance of UHPC Fully Encased Q690 High-Strength Steel Composite Stub Columns

To investigate the axial compression performance and strain compatibility of UHPC fully encased Q690 high-strength steel composite stub columns, this study designed, fabricated, and tested seven specimens under axial compression. The research parameters included the internal arrangement of steel wire mesh, the volume content of UHPC steel fibers, the stirrup spacing, and the cross-section type of steel profiles. It investigated the deformation failure process, ultimate failure mode, and peak bearing capacity of each specimen. The results showed that the UHPC fully encased Q690 high-strength steel composite stub columns exhibited excellent axial compression bearing capacity and deformation performance, and the strain compatibility between core UHPC and Q690 high-strength steel can be achieved at peak load. By referring to the bearing capacity calculation methods mentioned in various national codes, including China, Europe, and the United States, theoretical calculations of the axial compression ultimate bearing capacity of the UHPC fully encased Q690 high-strength steel composite stub columns were conducted and the results were compared with the experimental results. It shows that Tthe calculated results are in good agreement with the experimental results, providing a reference for calculating the axial compression bearing capacity of UHPC fully encased Q690 high-strength steel composite stub columns.