Effect of mass parameter on vibration displacement of beam member under air blast loading

By exploring the effect of mass parameter on the vibration displacement of beam members under air blast loading, an effective method was proposed to reduce the vibration displacement of beam members by increasing mass. An equivalent single degree of freedom (SDOF) system was used to analyze vibration displacement for beam members. The displacement formulas with mass parameter for flexible and rigid beam members in each stage under air blast loading were respectively established. These stages included elastic forced vibration, elastic free vibration, plastic forced vibration, plastic free vibration, and rebound vibration. Rectangular and circular sections were selected as typical cross sections of beam members, and 13 typical calculation cases with mass parameters ranging from 1.00 to 1.20 were designed. The vibration displacement-time history curves, maximum elastic displacement, maximum elastic-plastic displacement, and residual deformation were calculated and analyzed. Taking the data with a mass parameter value of 1.0 as the reference value, the displacement reduction rate of other calculation cases relative to the reference value could be obtained. The difference between the types of beam members for displacement reduction rate was further analyzed. The results are as follows. For flexible and rigid beam members subjected to air blast loading, increasing the cross-sectional area and considering only the mass parameter will result in a smaller reduction in vibration displacement. Therefore, the displacement should be analyzed according to the coupling effect of the mass parameter and additional stiffness parameter. For beam members with rectangular cross-sections, the reduction ranges of maximum elastic displacement, maximum elastic-plastic displacement, and residual deformation calculated from the coupled effect of mass parameter and stiffness parameter are about 4.75, 3.28, and 2.96 times that of mass parameter alone. For beams with circular cross-section, the data are 3.75, 2.56, and 2.32 times. These conclusions apply to both flexible beam members and rigid beam members, and there is no significant difference.