Effects of bolt hole clearance on sway deflections of cold-formed steel portal frames

Andrzej M. Wrzesien, Pouya Pouladi, James B.P. Lim, Michael Grimes, Brian M. Broderick, Daniel P. McCrum

Research output: Contribution to conferencePaper


This paper presents test results from a series of monotonic tests on full-scale cold-formed steel (CFS) moment resisting frames. The structural capacities are obtained from pushover failure tests and frames horizontal stiffnesses under characteristic loads are obtained from both monotonic and cyclic tests. A series of seven monotonic pushover tests and six cyclic tests were performed on three different section sizes of CFS portal frame. Two types of bolted connections were used, one with hole diameters the same as bolts diameter (true fit joints) and second with holes of standard tolerances (standard joints). Results demonstrated that joint type had negligible effect on the frame overall resistance under the
horizontal load. All of the frames failed due to bucking of the column web at the location where the maximum compressive stresses were expected. It was also demonstrated that the friction between steel galvanised plates can significantly improve joint rotational stiffness thus reduce frame deflection. Frames with true fit joints have demonstrated horizontal stiffnesses which were on average 28% greater than stiffnesses of frames with standard joints. The slip of bolts in standard tolerance holes contributes largely to horizontal deflections of frames with standard joints. It was shown in cyclic tests that only one out of six frames delivered a required residual deflection below 20% after the load was removed. It was also recorded that frames with standard bolt hole tolerances had residual deflections between 11% and 46% greater than frames with true fit bolts. In this paper, accuracy of published analysis methods for simulating sway behaviour of CFS portal frames with ‘bearing type’ connections was compared against test data. In terms of three analytical methods for predicting joint rotational stiffness, mixed accuracy was obtained. The ‘EC3’ model matched closely load-deflection curves for low-resistance frames but under predicted deflections of medium and high-resistance frames. The joint rotational stiffness model proposed in this paper, was found to represent the lower bound of frame stiffness (conservative solution). In comparison with some test results however, frames deflections were largely overestimated by the proposed analysis model.
Original languageEnglish
Number of pages1
Publication statusPublished - 5 Sep 2018
EventInternational Conference on Engineering Research and Practice for Steel Construction 2018 - Cordis Hotel, Hong Kong, China
Duration: 5 Sep 20187 Sep 2018


ConferenceInternational Conference on Engineering Research and Practice for Steel Construction 2018
Abbreviated titleICSC 2018
CityHong Kong
Internet address


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