Block planning based on grid's topology for the dismantling of long-span spatial lattice structures

The demolition issue of long-span spatial lattice structures has become increasingly prominent with the rapid urban development and building upgrades. Building deconstruction offers superior economic and environmental benefits compared to traditional demolition and therefore should be further promoted and applied. Dismantling in blocks is an efficient approach for deconstruction of long-span spatial lattice structures, surpassing the practice of dismantling individual components one by one. However, dividing the entire structure into substructures considering the convenience and safety of dismantling operations is the first challenge of dismantling in blocks yet to be overcome. In this study, a block planning method was proposed to aid practitioners in making high-quality block schemes. The topological relation of spatial grids defined by the adjacency matrix is the basis. The comprehensive evaluation index was established reflecting the operability, efficiency, and safety of the block scheme. Taking the combination of spatial grids as the variable and the comprehensive evaluation index combined with constraint functions as the objective, the block planning was formulated as an optimization problem. The genetic algorithm was adopted to solve this problem, and two examples were presented for verification. Results confirmed that the proposed block planning method is effective to generate the high-quality block scheme that meets topology, quantity, and lifting weight requirements and has great synthetical performance. The consideration of structural symmetry can accelerate the optimization process. The zoning planning strategy provides a tool for practitioners to make the block scheme that meets the lifting weight requirements of different zones when the crane's lifting capacity is limited by operating space. The proposed block planning method will enrich the construction management technologies of dismantling projects and help engineers make efficient and wise decisions.