Experimental and theoretical studies on the stability of steel tube–coupler scaffolds with different connection joints

• Four steel tube and coupler scaffolds were constructed and tested in the lab.
• The strengths and failure modes with different connection joint were obtained.
• An advanced nonlinear finite element analysis method was presented.

This paper presents a systematic experimental and analytical study on the stability behavior of steel tube–coupler scaffolds (STCSs), wherein upper horizontal tubes transfer construction loads. Four specimens with common geometric sizes were constructed and tested statically in the lab to obtain the strength and failure modes. Advanced nonlinear finite element analysis, which considers the initial member imperfection and semi-rigid behavior of right-angle couplers, was conducted on the specimen models by using ANSYS to obtain the stress distribution, strength, and failure modes of the STCS. Analysis results were compared with the experimental results. The following can be concluded from the experimental and analytical results. (1) The main failure mode of the STCSs is the local instability of a vertical steel tube if the upper layer joints have sufficient anti-slipping capacity. Otherwise, the main failure mode is the slipping and fracture of right-angle couplers. (2) The strength of STCSs is sensitive to upper joint type. The load capacity of ST2 with the strengthened joint is 1.30 times that of ST1 with a common joint, and the load capacity of ST4 with a common joint is 1.16 times that of ST3 with a weak joint. (3) The numerical simulation method presented in this paper is generally consistent with the full-scale test results and has a maximum difference of 11.08%.