Title: Stretch Length Anchor Bolts under Combined Tension and Shear
Author(s): Joel E. Parks, Chris P. Pantelides, Luis Ibarra, and David H. Sanders
Publication: Structural Journal
Appears on pages(s): 1317-1328
Keywords: anchor bolt; biaxial testing; concrete anchor; ductility; seismic; shear; stretch length; tension
Yielding of anchor bolts is a source of ductility in the seismic response of structures found in industrial facilities including tanks, circular vessels, and nuclear storage containers. Satisfactory seismic performance of anchor bolts with a stretch length has prompted ACI 318-14 to recommend their use with a stretch length of eight bar diameters, based on empirical evidence. In this study, individual ductile anchor bolts with stretch lengths of four, six, and eight bar diameters are tested to examine their performance under cyclic loads under combined tension and shear loads. Two types of steel chairs for connecting the anchor bolts to circular vessels were used: an elastic steel chair designed according to American Petroleum Institute Standards, and a steel chair designed to yield. The experiments show that, under combined cyclic tension and shear loads, anchor bolts with a stretch length of at least four bar diameters create a ductile connection compared to a conventional anchor bolt, while maintaining a similar tension and shear load capacity. At high shear-to-tension load ratios, the maximum tensile displacement capacity is reduced. A yielding steel chair is found to increase the displacement capacity and decrease the stiffness of the connection compared to an elastic chair.