Joints in cold-formed steel framing structures are usually designed as bolted lap type ones with a gusset plate. Unlike the end-plate joints in hot-rolled structures, the load in such joints is transferred through shearing of the bolts and bearing of the material. The prediction of their structural properties may be problematic in viewof unfavourable influence of the hole clearance and hole ovalization resulting from low bearing resistance of thin walls. A few experimental programmes showed that these issues lead to a different behaviour of the whole joint comparing to common end plate type. These concerns may be particularly important for joints under variable loading, which are prone to deterioration of structural properties. The testing programme conducted by the authors was focused on their behaviour under monotonic and cyclic loading with attention to a potential drop of resistance and stiffness. Monotonic tests revealed quite similar course of the joints’ response. In view of high deformability of the specimens at the intermediate stage of each monotonic test, plastic moment resistances of joints were associated with the initial part of the moment-rotation curves and were multiple times lower than maximum moments obtained in the experiments. The quantities of deterioration of structural properties were determined based on cyclic tests. Drop of resistance and stiffness was observed for several levels of loading range, but the trend of decrease varied for each property. Application of the DIC technique allowed one to identify qualitatively and quantitatively the sources of joint deformability.

The treelike structure links members and transfers loads via its solitary cast steel joint with branches. Therefore, the joint’s bearing capacity significantly affects the treelike structure’s stability, security, and economics. This paper utilized experimental verification and numerical modeling to examine the mechanical behavior of cast-steel joints with branches in the treelike structure under various loading conditions. Then, researchers investigated the failure process and mechanism of joints, and the three most common failure modes were outlined. Furthermore, the researchers proposed the bearing capacity calculation formula based on the common failure modes. The results show that the three common failure modes of the cast-steel joints with branches under different loading conditions are the failure in the joint core area under the axial load, the failure in the main pipe compression side under eccentric load, and the failure in the compression side of the single branch pipe root when the single branch pipe is under the uneven load. The suggested empirical calculation method can serve as a reference point for similar engineering practices design.