This research investigates the experimental behavior of an adjustable bolted steel plate connection under ultimate loads. The connection is comprised of prebent plates (cold bent to defined angles using a press brake) that are adjusted in the field to account for additional angles or manufacturing and erection tolerances by further bending via bolt tightening (Gerbo et al. 2018). It forms a moment-resisting joint between wide flange steel members by connecting flanges independently in double shear (webs would also be connected through a conventional bolted connection), with potential applications in building or bridge structures. The power of this approach lies in the kit-of-parts system, where a few types of prefabricated cold bent plates can be used to construct a large variety of angled connections. This research is also pertinent to misaligned (non-flush) bolted connections (for which force-fitting is typically used in the field) and for any double-shear connections using cold bent plates.
Prior research has investigated the behavior of the plates during prefabrication (Gerbo et al. 2016) and during field installation by bolt bending (Gerbo et al. 2018). This presentation will focus on an experimental investigation of the behavior of the connection under applied ultimate loads. Connections are loaded to failure via hydraulic actuators to measure elastic and nonlinear responses. Three dimensional (3D) digital image correlation (DIC) is used to measure strains induced in the bolts and plates, as well as to monitor displacement and slip of the connection during loading, providing unprecedented information on the behavior of bolts in slip critical connections. Experimental tests are performed at 1/3 scale under applied tensile and compressive axial loads. Control scenarios with flush plies are also investigated for comparison. The impact of the amount of bolt tightening, member connection angles, amount of field bending, and gap between members are investigated. The impact of these parameters on the elastic and nonlinear characteristics of the connection will be presented.
The results of experimental testing are used to draw conclusions and make recommendations regarding: 1) field installation procedure, 2) connection design strength, and 3) connection geometric parameters for the implementation of the adjustable connection. Audience members will also take away an improved understanding of the behavior of slip-critical bolted connections.
This material is based upon work supported by the National Science Foundation under Grant No. CMMI-1351272. The support of program managers Drs. Kishor Mehta and Y. Grace Hsuan is
Gerbo, EJ, Thrall, AP, Smith, BJ, and Zoli, TP (2016) “Full-field Measurement of Residual Strains in Cold Bent Steel Plates.” Journal of Constructional Steel Research, 127: 187-203.
Gerbo, EJ, Wang, Y, Tumbeva, MD, Thrall, AP, Smith, BJ, and Zoli, TP (2018) “Behavior of an Adjustable Bolted Steel Plate Connection during Field Installation.” ASCE Journal of Structural Engineering, 144(3): 04017223.