## 5 Conclusions  
By setting different time differences between rows of columns, the influence law of time difference on the blasting effect was studied, and the purpose of improving the blasting effect was achieved. This provides a reference for reducing the recoil distance, reducing the height of explosive piles, and effectively controlling the explosive pile range of buildings, and will reduce project costs and improve the safety of subsequent construction. The results of this research are as follows. 1. The structural plastic hinge is formed at the end of the latter span beam at a time difference of 0.1-0.3 s, moves down to the top of the rear row of the first-floor columns at a time difference of 0.4-0.8 s, and finally moves to the end of each span beam at a time difference of 0.9 s. The position of the structural orientation axis is influenced by the position of the plastic hinge, which is located at the bottom of the rear column at time differences of 0.1-0.3 s and 0.9 s, and is in the same position as the plastic hinge at time differences of 0.4-0.8 s. The blasting effect is better when the plastic hinge of the structure is formed at the top of the rear layer of the columns;
2. The recoil distance shows a linear growth trend of \(\mathrm{d}=6.37+14\mathrm{t}\) at the time difference of 0.1-0.3 s, plunges between 0.3-0.4 s, and shows a parabolic growth trend of \(\mathrm{d}=-19.46\mathrm{t}^{2}+36.76\mathrm{t}-5.29\) at 0.4-0.9 s. For the small-aspect-ratio structure, the recoil distance is smaller at the time difference of 0.4-0.5 s for the extension;
3. The height of the burst pile is \(\mathrm{h}=21.87\mathrm{t}^{2}-31.46\mathrm{t}+18.73\), which represents a parabolic growth pattern. In a time difference between 0.5 s to 0.8 s, the height of the burst pile is relatively low;
4. For small-aspect-ratio reinforced concrete structures, a reasonable range for the intercolumn delay-time difference is 400-500 ms, and the optimal solution is 400 ms. The actual selected blasting solution has an intercolumn extension time difference of 500 ms, which is consistent with the numerical simulation results. In the actual blasting and demolition process, the impact of the blasting loads generated by explosives in the columns on the collapse of the structure is very complex, and some simplifications made in the numerical simulations are debatable and need further study. 1. Reinforced concrete structures were studied using the separated common node model. Thus, the differences in the mechanical properties of concrete and two steel materials are observed. However, the distribution of the vertical reinforcement and hoop reinforcement makes it difficult to maintain consistency with the actual project. Therefore, a more suitable model for the study of concrete material properties will require further research;
2. The ground is assumed to be a rigid body that does not allow for the analysis of the building's grounding vibrations caused by blast demolitions. In future simulations, the ground can be modelled as a suitable elastoplastic material;
3. A blast incision is formed by forcing the concrete units to fail directly, which does not reflect the damage and vibration to the surrounding structure when explosives are detonated inside the concrete. Therefore, the research and development on blasting materials using finite element software can be further strengthened. Methodology, W.G. ; Software, T.Y. and S.L. ; Writing--review and editing, H.S. ; Writing--original draft preparation, Y.K. All authors have read and agreed to the published version of the manuscript. This research was funded by National Natural Science Foundation of China, (Study on rock breaking process and mechanism of cutting blasting in deep high-stress rock roadway) grant number 51874189. The study did not require ethical approval. Not applicable. The data presented in this study are available on request from the corresponding author. The data are not publicly available due to [the privacy of the data].