Joint optimization of green low-carbon oriented flight launch strategy and towing operation plan

The evaluation of protective performance and optimization of the design of building structures under impact loading is a key issue of concern in the fields of national defense, civil engineering, and other military and civilian use. Lattice columns are often used as the main load-bearing components in engineering structures and are inevitably impacted by other unintentional loads under engineering service environments. In this paper, 1∶2 scaled-down secondary impact tests were carried out on lattice columns along different impact directions with the same impact energy each time and compared with single-impact lattice columns under the same total energy to analyze the force and deformation characteristics of the lattice columns under the impact loads. Then, based on the experimentally verified finite element model, a continuous secondary impact simulation was carried out on the foot-foot lattice column. The dynamic response of the lattice column subjected to two consecutive impacts with the same total energy was obtained, and the effects of different energy distributions on the impact force, residual displacement, and residual kinetic energy were analyzed. The results show that under the same total energy, the displacement of lattice columns under a single impact is greater than that of a secondary impact. The optimal energy distribution obtained by numerical simulation can reduce the residual displacement of members impacted along different directions by about 12%. When the lattice column is subjected to a larger proportion of energy for the first time or a smaller proportion of impact energy for the second time, the total energy absorbed by the column is smaller. Finally, based on the results of tests and numerical simulations, the maximum impact velocity at which the damaged column can withstand a second impact is proposed. The results of the study can provide a reference for the design method of lattice steel columns under such loading conditions.