平面ラチス梁の終局耐震性能に及ぼす静的安全率の効果

Abstract

Earthquake input energies have been discussed in considering seismic resistant capacities of structures. In the literature, it had been pointed out by the author et al. that potential energies due to self-weight and dead loads would be necessary to be taken into account in order to estimate the seismic resistance capacity in a good accuracy especially for beam type structures. The author presented an estimation method of ultimate seismic resistance capacity with the static absorbed energies considering potential energies. The method presented utilizes the two strain energies at an initial yield and a limit state, and a pseudo velocity response spectrum of seismic waves. Although it is based on an extrapolation method, it shows a good accuracy in the estimation of maximum input acceleration of seismic waves. The method includes a modification equation to improve the accuracy, considering the properties of elastic and plastic strain energies of structures during a pushover analysis. Then in this paper, the effect of static safety factors is investigated to make clear the meanings of coefficient in the modification equation, for lattice beams of two types, cross web type and warren type. As the results, a further modified estimation method is presented to predict the dynamic collapse level under excessive seismic motions with the information of pushover and free vibration analyses.