Experiment And Analysis On Load-bearing Capacity Of Steel Tubular Scaffolds With Bowl-button-type Connection

A new type scaffolding, the Buckles bowl scaffold is widely used nowadays. But the buckles bowl scaffold is following the Specifications of Tube-and-coupler Scaffold, and this brings problems on security.The author take the opportunity of editing the Safety and technical code for frame scaffoldings with Buckles Bowl in construction(JG166-2008), and based on the science project of Hebei provincial construction technology research & test on load of the overall structure of buckles bowl scaffold, studied the overall load of external scaffolding and internal braced frame of buckles bowl scaffold, and analyzed the ultimate bearing capacity. The main contents and results are as follows:(1) 6 groups of double buckles bowl scaffolds are designed. The ultimate bearing capacities and damage modes of the test specimens subjected to vertical loads and both horizontal and vertical loads are compared, and the influence regularities to the ultimate bearing capacities and damage modes of scaffolds led by horizontal diagonals and covered diagonals are obtained. Experimental results show that the horizontal load has more influence to bearing capacity and deformation of the scaffold, and it can significantly improve the bearing capacity and reduce the deformation when horizontal diagonals and covered diagonals are installed.(2) 8 groups of double buckles template braced frames are designed. The ultimate bearing capacities and damage modes of the national standard and the non national standard template braced frames are compared, and the influence regularities to the ultimate bearing capacities and damage modes of scaffolds led by horizontal diagonals, covered diagonals, bar gap, height, and aspect ratio are obtained. Experimental results show that the bearing capacity of non national standard template braced frame relay on the strength of joint, and the national standard template braced frame has a damage mode of overall instability. Bearing capacity of the braced frame decreases with the increment of the height, the gap and the aspect ratio of the bracing piece. Bearing capacity of the braced frame will increase efficiently if both the horizontal and vertical brace are installed.(3) 2 groups of buckles bowl joints are designed. Mechanical behaviors of national standard and non national standard buckles bowl joints are compared, and the damage order of buckles bowl joints and scaffold are obtained. The stiffness of buckles bowl joints are analyzed. Experimental results show that the bearing capacity of non national standard scaffold is determined by strength, and the damage of scaffold precedes to the damage of national standard buckles bowl joints. The buckles bowl joint, which is a semi-rigid connection, has a good mechanical behavior.(4) Ultimate bearing capacities and damage modes of bowl buckle scaffold and template brace are analyzed by finite element method and numerical results are compared with the experimental results. The calculation length formula of the member of bowl buckle scaffold is given.Achievements of this paper supply experimental and theoretical references for both the written of Safety and technical code for frame scaffoldings with Buckles Bowl in construction(JG166-2008)and design of the buckles bowl scaffold and the template braced frame.