In-plane stability of steel circular closed supports with I-section of sinusoidal corrugated webs: experimental and numerical study

Structural supports used for tunnels and other underground civil structures in soft rock are often prone to severe damage due to large deformation. To overcome this issue, a new steel circular closed support with I-section of sinusoidal corrugated webs is proposed to mitigate such damage caused by deformation. Large scale experiments of the proposed support with corrugated webs were carried out to investigate their buckling behaviors and failure modes. The results showed that the ultimate load of the support increased from 1386.25 kN to 1635.27 kN (18% increment) with the web height increasing from 240 mm to 300 mm (25%). Therefore, the web height had a positive effect on the bearing capacity of steel circular closed supports with I-section of sinusoidal corrugated webs. Finite element (FE) analysis was conducted and then validated by the experimental results. Take specimen YX-1 as an example, the differences between the FE modeling and experiment for the ultimate load-carrying capacity and vertical displacement at the vault were 2.64% and 3.34% respectively, when the support was in the ultimate state. The correlations between major design parameters including cross sectional dimensions, initial imperfections and slenderness ratios, and in-plane elastic as well as elastic–plastic buckling performances were also investigated. The results showed that corrugated web height, flange width and thickness were three dominant parameters for the structural design of such supports. Furthermore, the antisymmetric buckling mode was observed when the slenderness ratio increases to a certain level (>100 in this paper). A formulation was further proposed to estimate global elastic buckling load for such supports under hydrostatic pressure. In combination with the design method of I-section beams with sinusoidal webs under axial compression, a developed design approach for in-plane ultimate bearing capacity of the steel circular closed support with I-section of sinusoidal corrugated webs under pure pressure was obtained.