On the Influence of Loading History on Long-Term Behaviour of Concrete Elements

Long-term behaviour of concrete structures depends on various factors, including loading history. Over the past two decades, research at FCE Skopje has focused on understanding the influence of different loading histories on the long-term behaviour of full-scale elements made of normal-strength, high-strength, prestressed and steel fibre-reinforced concrete. This paper presents selected results from four experimental programs on RC simple-supported elements measuring 15/28/300 [cm], tested under four-point bending. Using a specialized test setup, the elements were subjected to permanent and variable repeated loads applied in alternating cycles lasting several hours. Results collected over a year in each experimental program show that variable loads can significantly influence the long-term behaviour regardless of the concrete type. Additional creep deformations depend more on load intensity than the duration of the applied load, while load pattern has minimal effect provided the maximum variable load intensity is included in the loading history.