TRANSFER OF TEMPERATURE LOADS IN PREFABRICATED STRUCTURES

Sammanfattning

This report investigates the transfer of temperature loads in prefabricated structures. The study is based on a case study of an industrial building in southern Poland where significant damage was observed during the construction stage. Cracks and concrete cover spalling occurred in the connections between steel roof trusses covered with trapezoidal steel sheeting and precast concrete girders as well as between girders and precast concrete columns. It is hypothesized that these damages were largely impacted by temperature-induced forces transferred through the joints. The aim of this project is to determine how stiffness and slip flexibility in joints between the steel sheeting and steel trusses affect the transfer of temperature loads to concrete members. A finite element model was developed in RFEM to simulate the structural behavior under relevant temperature loads. Both a main model and a sub-model were created to analyze displacements and internal forces in the critical areas where failures were observed. The sub-model was used for a parameter study to evaluate the impact of varying stiffness and slip flexibility values. In addition, experimental tests were performed at the laboratory at Cracow University of Technology, Poland. These tests measured stiffness and slip flexibility in joints between trapezoidal steel sheeting and steel beams, using both single and double sheeting configurations under static and cyclic loads. The data collected from the tests were used to define joint parameters in the sub-model. The experiments showed that stiffness values remain mostly constant under normal loading, while slip flexibility develops with cyclic loading due to ovalisation of the screw openings. The results from the numerical analysis and experiments indicate that joint stiffness significantly influence the magnitude of forces transferred from the steel sheeting to the concrete girders, whereas slip flexibility has no significant impact. High joint stiffness increases force transfer and the risk of concrete splitting in the supporting elements. The findings highlight the importance of accounting for joint behavior in structural design of prefabricated buildings exposed to significant temperature variation, especially in the case of non-insulated structures, such as open storage halls.