Experimental and numerical study on the cyclic behavior of connections in storage rack structures

Contrary to buildings which serve live loads lower than the self-weight, storage racks support much higher live loads than the self-weight. In unbraced frames of storage racks, the lateral stiffness and the stability along down-aisle direction are provided by means of beam-to-upright and base connections which are neither pinned nor fixed connections. Beam-to-upright connections govern the structural performance and stability of the whole system. Therefore, estimating the behavior of a connection, having knowledge about the failure modes and rotation capacity are of great importance. This study presents the main results of an experimental program on the response of beam-to-upright connections of racks commonly used in the Turkish market. The raw data are moment-rotation curves which characterize structural parameters of the joint. To create reliable references for comparing the results, beam-depth and end-connector types were tested for 2 different types of specimens, altogether 18 specimens were tested. Monotonic and slow quasi-static reversed cyclic tests were performed. Interlocked boltless beam-to-upright connections cause difficulties in collecting the data and measuring the parameters; therefore the testing procedures and originally developed set-up for beam-to-upright connections were proposed and modeled with FE models developed in SAP2000 v.15 software to establish reliable references. Numerical investigations were used to verify experimental results and to introduce a model of such connections considering various parameters. To simulate the test and to model the connection, ANSYS v.14 software was used. The semi-rigid nature of this type of connections which primarily is due to the unpredictable distortions at different components of the joint requires a nonlinear simulation through advanced analyses. ANSYS software results showed a good match with moment-rotation curve results with respect to initial stiffness, ultimate strength and the level of ductility.