阻尼对空爆荷载等效静载动力系数的影响

为考查阻尼参数对空爆荷载等效静载动力系数的影响，理论推导了空爆荷载下结构等效单自由体系弹塑性位移解及延性比解，设计并计算了阻尼比0.000 1～0.1、延性比1～4的20种典型工况的动力系数，并与现行抗爆设计规范动力系数公式结果进行了对比。结果表明:阻尼比小于0.000 1时可基本代表无阻尼状态，阻尼比0.01的动力系数比无阻尼的最大降低幅度为2.08%，数值差异很小，因此阻尼比为0.01以内时，可忽略阻尼对动力系数的影响；阻尼比0.05的动力系数比无阻尼的降低幅度约9.92%，数值差异较大，认为阻尼比0.05以上时将具有明显的经济效益；现行设计规范动力系数更适用于柔性结构体系，运用于刚性结构抗爆设计时，计算误差较大，对阻尼比较小的结构设计更不利。

Effect of damping on equivalent static load dynamic factor of air blast load

In order to examine the effect of damping on the equivalent static load dynamic factor of the air blast loading,the solutions of the elastoplastic displacement and ductility ratio were derived by the structural equivalent single degree of freedom(SDOF)method for the air blast loading.According to the relationship between the duration of the air blast loading and the duration required for the structural members to complete elastic vibration,the members are divided into two types:rigid members and flexible members.Twenty typical calculation cases,including damping ratios from 0.0001 to 0.1 and ductility ratios from 1 to 4,were completed and compared with the dynamic factor formula results of the current blast resistant design code.The results show as follow.A ductility ratio less than 0.0001 can be regarded as a state without damping.The relative error of the dynamic factor between the calculation results with a damping ratio of 0.01 and without damping is less than 2.08%.This relative error is so small that the damping effect with a damping ratio less than 0.01 can be ignored.The dynamic factor with a damping ratio of 0.05 is about 9.92%lower than the one without damping.This relative error is so great that considering the damping ratio will have obvious economic benefits for the blast resistant design when its value is greater than 0.05.Based on the elastic design,the calculation results from the current blast resistant code formula are in good agreement with those from the derived formula in this paper,and the value of the dynamic factor calculated from the code is between the results of damping ratios of 0.01 and 0.05.Furthermore,the current air blast resistant design code formula is more suitable for flexible structure systems.When the code formula is applied to calculate the dynamic factor of rigid members,there will be a large calculation error,which is more unfavorable for members with small damping.