Abstract:

In order to study the influence of stirrup constraint effect on axial compression performance of ultra-high strength concrete precast column，an axial compression contrast experiment between full-size ultra-high strength concrete column and the ordinary column were carried out．Based on the experiment，36 full-size ultra-high strength concrete columns were designed in finite element analysis to investigate the effects of stirrup form，stirrup spacing，and stirrup diameter on the compression performance of ultra-high strength concrete columns．By considering the constraint effect of stirrup，a modified calculation formula of axial compression capacity of ultra-high strength reinforced concrete column was proposed．Furthermore，it was compared with the calculation formula in Code for Design of Concrete Structure．The results showed that：the ultimate bearing capacity of equal-strength designed ultra-high strength concrete column is higher than that of ordinary concrete column．But it is more brittle than ordinary concrete，especially when reaching the ultimate bearing capacity，the concrete of ultra-high strength concrete column breaks more obviously than that of ordinary concrete column; the constraint effect of stirrup on the core area concrete can improve the axial compressive bearing capacity of ultra-high strength concrete column，and stirrup type，stirrup spacing and stirrup diameter can influence significantly the axial compressive ultimate bearing capacity and peak compressive strain of ultra-high strength concrete column; compared with the calculation formula of Code for Design of Concrete Structure，due to the consideration of the constraint effect of stirrup on the core area concrete，it can better use of material by using the proposed calculation formula to assess design value of axial compressive capacity of ultra-high strength concrete column.

Key words: UHSC, axial compression, constraint of stirrup, modified bearing capacity formula, confined concrete