Investigation of the abnormal flexural deformation of assembled H-shaped steel strut

Assembled H-shaped steel strut (AHSS) was applied in a deep excavation project. During the excavation process, abnormal flexural deformation of one AHSS was found. To evaluate the safety redundancies of the AHSS when its axial force reaches the designed level, a field axial loading test was conducted. It was found that, due to the weak region around the loading component, the horizontal and vertical displacements were larger for the monitoring points closer to the loading component. Steel columns showed a negligible contribution to the restriction of the horizontal displacement but relatively good vertical support of the AHSS. As compared with the normal deformation condition, the safety redundancies of the AHSS were all smaller when considering the abnormal deformation. However, the AHSS was still in a safe condition when its axial force slightly exceeded the designed value. To assess the contribution of different components of AHSS to flexural deformation and reveal the mechanism of abnormal flexural deformation, a simplified numerical simulation was conducted. The difference in horizontal movement of the wale at the two sides of each end of AHSS was found to be the leading factor causing the abnormal flexural deformation. Suggestions for avoiding such abnormal flexural deformation were given.