Shear resistance of cold-formed thin-walled steel inter-story connections

A composite wall is the primary lateral force-resisting system in a cold-formed thin-walled steel structural sys-tem. The shear force between the upper and lower walls is transmitted through an inter-story connection in the cold-formed thin-walled steel platform framing system. In this study, the 16 platform framing inter-story connection specimens were subjected to cyclic loading to study the shear resistance, the failure modes, deforma-tion, and the influence of stiffeners, lateral rigid blocking, X-shaped straps, and vertical. Hysteretic curves, skele-ton curves, shear bearing capacity, and lateral stiffness values were obtained from the testing. The results showed that the specimens with only stiffeners had a lower shear capacity and lateral stiffness, which were significantly affected by the vertical force. Further, short stiffeners were not fully effective. The highest shear capacity and lat-eral stiffness values were characterized for the specimens with rigid blocking. Increasing the rigid blocking im -proved the shear resistance of the specimens, and rigid blocking with the same height as the floor joists contributed to excellent shear capacity and lateral stiffness of the specimens under vertical loading. The lateral stiffness of the inter-story connection was also significantly increased by using X-shaped straps, and the vertical force resulted in substantial decrease of the lateral stiffness. Based on the test results anda comparison of the nominal shear strength values required by current specifications, this study proposed improvements to the de-sign of cold-formed thin-walled steel platform framing inter-story connections. (c) 2021 Elsevier Ltd. All rights reserved.