基坑工程钢支撑端节点新型结构设计及力学性能分析

New Structural Design and Mechanical Properties Analysis of Steel Support End Joints in Foundation Pit Engineering

大量基坑工程事故调查表明,钢支撑体系的破坏往往发生在端部连接处,端部节点弱化是造成钢支撑体系失稳甚至引发基坑连续坍塌破坏的主要原因。因此,从根本上解决端部节点弱化问题是控制围护结构变形和保证基坑稳定的关键所在。首先论述了广泛采用的传统钢楔式活络头的结构设计、力学性能和适用性;然后针对现阶段3种代表性的新型活络头——摩擦型活络头、螺栓紧固型活络头和钢板拼接型活络头,基于现有室内试验、数值模拟和工程现场监测等数据,提出了新型活络头的承载力和刚度等力学性能指标,并详细分析了其结构特点、工作原理、承载性能及适用条件;最后针对钢支撑端部节点弱化问题进行革新设计,提出一种钢支撑高脚螺栓-模袋混凝土固支端结构方案,阐述了固支端结构设计方案和受力原理,并采用有限元模拟手段研究了固支端的力学性能,结果表明固支端结构具有受力合理、承载力高、性能可靠、施工便捷的特点,尤其是可以消除偏心荷载的作用,具备推广应用价值,为基坑工程钢支撑端节点的设计和施工提供了选择。

A large number of foundation pit engineering accident investigation shows that the failure of the steel support system often occurs at the end connection,which is the main reason for the instability of the steel support system and even the continuous collapse of the foundation pit.Therefore,that fundamentally solving the problem of end node weakening is the key to control the deformation of retaining structure and foundation pit stability.This paper discusses the structural design,mechanical properties and applicability of traditional steel wedge-type active head which is widely used.In view of three new representative types of active head at the present stage of frictional active head,bolt-fastened active head and steel plate spliced active head,the mechanical properties indexes of bearing capacity and stiffness of the new type active head are proposed based on the monitoring data of laboratory test,numerical simulation and engineering field of existing research.And the structural characteristics,working principle,bearing capacity and applicable conditions are analyzed in detail;Finally,an innovative design is carried out for the weakening of the steel support end node,and a structural scheme of the steel support high-foot bolt-bag concrete fixed end is proposed.The structural design scheme and force principle of the fixed end are expounded.The mechanical properties of the fixed end are studied by the finite element simulation method.The results show that the fixed end structure has the characteristics of reasonable force,high bearing capacity,reliable performance and convenient construction.In particular,it can eliminate the impact of eccentric load and has the value of popularization and application,which can provide a choice for the design and construction of the steel support end node in foundation pit engineering.