Determination of the flexural behavior of steel storage rack baseplate upright connections with eccentric anchor bolts

The baseplate upright connections of the steel storage racks are often attached to the concrete floor by anchor bolts possibly at an eccentric location. Currently available rack design specifications do not provide any guidelines to take account of the influence of eccentric anchor bolt location and do not consider the associated baseplate behavior in the design of such storage rack base connections. The first part of this paper experimentally established the flexural behavior of the baseplate upright connections with eccentric anchor bolts. The experiments considered an enhanced test setup and five groups of three nominally identical test specimens. Influencing parameters such as the baseplate thickness, anchor bolt size, the bracket thickness and the upright thickness were studied. The experimental observations revealed that the baseplate eccentric anchor bolt assembly plays a dominant role on the flexural behavior of the entire baseplate upright connections. The rotational stiffness, the failure mode and the moment capacity of the base connections are strongly intertwined with the eccentric anchor bolt location as well as the baseplate bending behavior. In order to further understand the behavior of such connections, in the second part of the paper, a component-based analytical model is established to predict the initial rotational stiffness and the progressive post yielding rotational stiffnesses of the baseplate upright connections. The moment capacity of the connections is also determined using a deformation limit-based method. The analytical model gives only a 3% underestimation of the initial stiffness and a 3% overestimation of the moment capacity compared with experimental results. The proposed model is suggested to be incorporated in future rack design specifications so that the model can be used by the rack designers to analytically determine the behavior parameters of the eccentric anchor bolted baseplate connections. The rack designers can also use the proposed model to identify the deformation contribution of each individual component and to develop a multi-linear moment-rotation relation of the baseplate upright connections without resorting to the physical experimental tests. Parametric studies were also performed using the proposed analytical model and the influence of relevant parameters had been quantified. Doubling of the baseplate thickness may result in a 11–37% increase in the initial rotational stiffness of the considered baseplate upright connections.