Critical Wind Speed Analysis of Large-section Steel Box Girder Lifting in Urban Areas Based on Lifting Offset

This study takes the lifting of steel box girders for interchanging traffic in a certain area as the research background, and considers the limitation of lifting by the surrounding buildings during the lifting process. Combined with the topographic environment and climatic conditions where the project is located, based on the key technology of large-section steel box girder lifting construction, the displacement change of large-section steel box girder lifting under different wind speeds is explored. To this end, a method for calculating the lifting offset is proposed, aiming to provide guidance for the safe construction of large-section steel box girder lifting in urban areas. Meanwhile, the concept of critical wind speed is introduced in this study to determine the critical conditions in the lifting process, i.e., the lifting process may be unsafe when the wind speed reaches the critical wind speed. The results show that the average displacement of the most unfavourable member increases from 0.024m to 1.541m when the wind speed increases from 3m/s to 27m/s; under the same wind speed, different area to mass ratios have a greater effect on the member displacement; considering the safety of the lifting construction, it is recommended that the value of the critical wind speed should be taken as 17m/s, and it is recommended to stop the lifting of the member or to strengthen the safety measures when the wind speed is greater than the critical wind speed during the lifting process. By analysing the change of lifting displacement and critical wind speed, this study provides an important reference and decision-making basis for the construction safety of large-section steel box girder lifting in urban areas.