On the influence of loading history on long-term behavior of concrete elements

Long-term behavior of concrete structures depends on various factors, including loading history. Well- structured long-term experiments are essential to study the effects of loading history. Over the past two decades, research at FCE Skopje has focused on understanding the influence of realistic loading histories on the long-term behavior of full-scale elements made of normal-strength, high-strength, prestressed, and steel fiber-reinforced concrete. This paper presents selected results from four experimental programs on RC elements measuring 15/28/300 cm, tested under four-point bending. Using a specialised test setup, the elements were subjected to permanent and variable repeated loads applied in alternating cycles lasting several hours. Results collected over a year show that variable loads can significantly influence the long-term behavior 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.