Multi-Objective Optimization Method and Asynchronous Influence Law for the Integral Lifting of Spatial Steel Structures

Aiming at the complexity and difficulty in optimizing integral lifting schemes for spatial steel structures， this paper proposes a multi-objective optimization method for such lifts. This method constructs a multi-objective function centered on structural safety and lifting equipment capacity， and integrates the optimization variable representation method of real-integer coding and iterative decoding algorithm into the optimization framework， thereby solving the efficiency and feasibility issues of large-scale combinatorial optimization. An irregular rectangular frame truss structure was taken as an engineering case to analyze the mechanical response of large-scale steel structures during the integral lifting stage in detail. The lifting scheme obtained by the proposed method not only reduced the number of lifting points but also significantly decreased the structural strain energy， stress level， and lifting reaction forces during the lifting process， fully verifying its engineering effectiveness. Furthermore， the iterative limit boundary method was employed to conduct asynchronous lifting analysis on optimized solutions. The results demonstrated an inverse proportional relationship between the number of lifting points and the allowable asynchronous height difference limit. Compared to the traditional trial method， the iterative limit boundary method yielded stricter height difference limits. The multi-objective optimization system constructed in this paper features a parameter-adjustable universal framework. By flexibly adjusting the dimensions of decision variables， constraint conditions， and parameters of the objective function， it can adapt to the optimization of lifting schemes for spatial structure-equipment systems of various shapes.