Cyclic tests of beam-upright connections in racking systems with a new hybrid procedure

Some disadvantage and incompleteness of the current test recommendations for the assessment of low cycle fatigue behavior are discussed, particularly in what regards the ultimate bearing capacity with respect to real loading conditions. Moreover it is considered the difficulty of current procedures to represent the real behavior of elements and details when subjected to seismic loads, considered as a series of opposite impulsive loads, which generally induce a cumulative displacement in one direction. In order to overcome these problems, a new testing procedure is proposed, and its application to the assessment of the low cycle fatigue behavior of typical beam-upright connections in storage rack systems is discussed in the paper. The proposed cyclic test is a hybrid procedure with an initial force-controlled part, up to the gravitational load applied, and a final displacement-controlled part. The aim of the new procedure is to take explicitly into account the actual exercise load and its influence on the cyclic behavior, pointing out particularly the cumulative displacements, and to define an effective collapse condition based on exercise load.