Abstract: As a highly flexible passive support structure，mining I-beam trapezoidal support has been widely used in underground support. In practical application，construction defects and surrounding rock deformation may lead to the working state of trapezoidal support under asymmetric load during ser⁃ vice，which is not conducive to the full play of its strength. In view of this，a four-point loading test of 12# I-beam is carried out in this paper. Based on the ABAQUS/explicit，a refined finite element model of full�size I-beam trapezoidal support structure is established，and its response behavior under different loads (especially under asymmetric loads on both sides) is studied. The results show that the mining 12# I-beam has good stability and bearing performance，and some areas of the mid-span web remain elastic when the deflection-span ratio reaches 4.4%. The deformation of the top beam is proportional to the vertical load and inversely proportional to the lateral pressure load，and the deflection deformation of the column leg is main⁃ ly affected by the lateral pressure load. The asymmetric load makes the column leg of the trapezoidal brack⁃ et rotate. The change of the support condition and the boundary bending moment leads to the lateral dis⁃ placement rate of the bracket far exceeding 2% when the load coefficient difference between the two sides is 0.2，which is at the risk of collapse. At the same time，the top beam produces asymmetric deformation. When the load coefficient difference between the two sides is 0.4，the maximum vertical displacement in⁃ creases by 170.5% compared with the symmetrical load. In view of this，the stable contact between the sup⁃ port and the surrounding rock mass should be fully guaranteed in practical engineering.

Key words: support of roadway, mining I-beam, trapezoidal support structure, asymmetric load