Service and Ultimate Behavior of Adjustable Bolted Steel Plate Connections

This paper experimentally and numerically investigates the service and ultimate behavior of adjustable bolted steel plate connections—slip-critical, splice plate connections that can join wide flange sections at a range of angles as well as adjust in situ to achieve additional angles or compensate for erection and fabrication tolerances. The connection is comprised of plates that are cold bent by a press brake to a specific set of angles, forming a prefabricated, kit-of-parts. Adjustability is achieved by further cold bending the plates in the field through bolt tightening. The slip and bolt shear behavior of the connection was experimentally tested by applying an axial force on a wide flange member (via a servo-controlled hydraulic actuator in displacement control) joined by the tested connection to another wide flange member (restrained by a rigid reaction frame). A total of 18 scenarios were tested to investigate the effect of (1) the direction and amount of cold bend via bolt tightening, (2) tightening approaches, (3) the direction of loading, and (4) the plate and member angle on the behavior. A finite-element numerical modeling approach was developed and validated, offering additional understanding of bolt behavior in the adjustable bolted steel connection. A degradation in slip capacity was observed due to a reduced clamping load. During bolt tightening, the bolts deform nonflush plies into contact with the flanges and are simultaneously being bent by contact with the plates, leading to this reduced clamping load. The bolt shear capacity can also be degraded due to the connection geometry, which can reduce the engagement of the shear planes. Recommendations for reductions in slip and bolt shear capacity are developed. Importantly, findings also offer insight into the behavior of bent connections, as well as misaligned or nonflush connections that are force-fit in the field.