基坑工程PC-CFST内支撑及其设计方法

PC-CFST Inner-bracing and Its Design Method for Braced Excavations

结合明挖地铁车站基坑工程特点,提出了由3根圆钢管混凝土柱组成的装配式组合钢管混凝土内支撑(简称PC-CFST),并阐明了其优点及适用范围;针对PC-CFST内支撑结构和受力特点,归纳了其承载能力、螺栓受力、预埋件受力、挠度等设计验算方法;以某城市轨道交通车站标准段基坑工程为背景,设想将原设计方案中的第1道钢筋混凝土支撑换为PC-CFST支撑,结合理正深基坑计算软件对基坑变形及内支撑受力进行验算,并通过造价分析,对比了本文设计方案与原设计方案的经济性。研究结果表明:PC-CFST内支撑结构简单,设计合理,可拆装复用,节省工期,造价低,具有推广应用前景。

In this paper,combining with the characteristics of deep excavation engineering for open-cut subway station projects,the Prefabricated Composite Concrete-Filled Steel Tube( PC-CFST) composed of three concrete-filled steel tubular columns was developed and its advantages and scope of application were expounded. In the light of the structural and mechanical characteristics of PC-CFST,its design and checking methods for bearing capacity,bolts strength,embedded element strength and deflection were established. On the basis of the design information of a subway station,it was assumed that the first raw of reinforced concrete inner-bracings in the original design scheme were replaced by PC-CFST inner-bracing in the braced excavation,and its deformations and internal forces were calculated by Lizheng software. At the same time,the economical efficiency of the assumed scheme was compared with that of the original design scheme by engineering cost analysis. The results show that PC-CFST inner-bracing is of simple structure,reasonable design,removable and reusable,shorter construction period,and less cost,so it may have a good application prospect in the future.