Numerical and experimental study of beam-to-column steel joints under dynamic loading in low-rise prefabricated modular buildings

In the present paper the behavior and the structural performance of steel beam to column connections is investigated for an innovative type of low-rise prefabricated modular building system. The load bearing system is composed of lightweight steel frame members connected with double-shell composite walls that play the role of smart façade elements. Aiming to obtain a clear perspective of the dynamic performance of the system, a series of experimental and numerical tests of critical structural details such as the steel joints of the systems has been carried out. Two alternative types of steel beam to column specimens consisted of welded and bolted parts with differences in rigidity were tested in quasi-static cyclic loading in order to investigate their bearing capacity, as well as their hysteretic behavior. Using ANSYS software a three-dimensional nonlinear FEM model was developed and validated comparing the respective numerical results with the experimental results from the tested specimens. The same quasi-static cyclic loading history scheme was applied both for the numerical models and the test specimens to register the critical issues of the joint components under investigation. The obtained experimental and numerical results are presented and discussed in terms of moment-rotation response, failure mode, load-bearing capacity, ductility, and energy dissipation capacity. Moreover, the developed numerical models were used for the evaluation of the structural response of the system and for the optimization of the cost, the shape and the bearing capacity of the joint. With regards to energy dissipation capacity of the system under investigation, it is obvious that both the tested specimens as well as the respective numerical models absorb a significant amount of energy from the overall steel frame system of the composite modular structure.