End Deflection Control Ling Methods for Lifting Construction of Irregular Grids
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摘要: 对于端部存在“尖角”的不规则网架的整体提升施工,通常是采用在“尖角”区域增设提升器的方法来控制该区域的挠度。该方法虽然能很好地控制网架端部“尖角”区域的挠度,但该处提升器的提升反力往往很小,导致该处提升器对网架提升的贡献度较低,浪费施工成本。针对此现象,基于咸阳机场中央C区网架某分块提升工程,对不规则网架提升施工中端部挠度控制方法展开研究,分别提出了提升到位后和提升过程中两种不规则网架端部“尖角”区挠度控制方法。前者是利用汽车吊、手拉葫芦等机械在网架提升到位后对挠度较大的“尖角”区域施加竖向荷载,使该区域结构上翘,从而减小该区域挠度。该方法施工便捷,但对施工场地条件要求较高。后者是在刚度较大区域的结构上部设置支撑架,并利用钢丝绳将其与“尖角”区域进行拉结,以减小“尖角”区域在提升过程中的挠度。该方法可弥补提升到位后挠度控制方法受施工场地条件限制大的不足。通过施工仿真模拟分析了两种挠度控制方法的控制效果,同时也分析了提升过程中钢丝绳预拉力大小、支撑架高度、钢丝绳拉结点位置等因素对控制效果的影响。结果表明:1)采用提升到位后挠度控制方法时的结构挠度和构件应力与利用提升器控制的方法差异很小,表明两者的控制效果接近,且提升到位后挠度控制方法对结构影响较小。2)提升过程中采用挠度控制方法时,钢丝绳预拉力与控制效果呈正相关,可通过增大钢丝绳预张力改善控制效果;支撑架在一定高度以内,其高度与控制效果呈正相关。超过一定高度后,支撑架高度对控制效果的影响逐渐降低,甚至表现出负相关趋势;钢丝绳拉结点设置在结构刚度大、挠度控制要求较高的区域时,其控制效果较好。且增加拉结点数量,并均匀布置在拉结区,可提高控制效果。3)提出的提升到位后和提升过程中两种挠度控制方法具备可行性,同时可降低施工成本。Abstract: For the integral lifting construction of irregular grid structures with "sharp corners" at the ends, the method of adding lifter in the "sharp corners" area is generally adopted to control its deflection. Although this method can effectively control the deflection in the "sharp corner" area at the end of the grid, the lifting reverse force of the lifter at that location is often small, resulting in a low contribution of the overall grid lifting process and a waste of construction costs.Therefore, based on a segmented lifting project in Central Zone C of Xianyang Airport, this study investigated control methods for end deflection during the lifting construction of irregular grid structures.Two methods for controlling the end "sharp corner" deflection of irregular grid structures have been proposed, including after lifting in place and during the lifting process. The former method uses machinery such as car cranes and chain hoists to apply vertical loads to the "sharp corners" area with large deflection, after the grid is lifted into the target place, causing the structure in that area to arch upwards, thereby reducing the deflection of that area. This method is convenient for construction but requires high construction site conditions. The latter method involves setting up a support frame on the upper part of the structure in high-stiffness areas and using steel wire ropes to secure the "sharp angle" area, thereby reducing its deflection during the lifting process. This method can compensate for the shortcomings of the deflection control method, which is highly limited by on-site construction conditions after the lifting process.This paper analyzed the effects of two deflection control methods through construction simulations, and also analyzed the influence of factors such as the pretension force of the steel wire rope, the height of the support frame, and the position of the tensioning node on effectiveness of the deflection control methods during the lifting process. The results showed that: 1) the difference between the structural deflection and component stress by the deflection control method after lifting in place, and by the lifters was very small, indicating that the deflection control method after lifting in place had a small impact on the structure; 2) when using the deflection control method during the lifting process, the pretension force of the steel wire rope was positively correlated with the control effect, indicating that the control effect could be improved by increasing the pretension force of the steel wire rope; the height of the support frame was positively correlated with the control effect within a certain height range, after exceeding a certain height, the impact of the support frame height on the control effect gradually decreased and then even exhibited a negative correlation; when the steel wire rope tensioning node was set in an area with high structural stiffness and stringent deflection control requirements, the control effectiveness was optimized, and increasing the number of tensioning nodes and evenly arranging them within the node area could improve the control effectiveness; 3) the two deflection control methods proposed in this paper for post-lifting and during-lifting stages was proved to be feasible and cost-reducing.
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Key words:
- irregular grid /
- integral lifting /
- deflection control /
- construction cost
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