Experimental Investigation on Short- and Long-Term Deformations of Cracked Reinforced Concrete Ties

Abstract

The current study reports the test results on deformations of cracked reinforced concrete (RC) ties. Four ties were tested under shortand long-term loading for 315 days. To perform the long-term tests, four testing rigs were constructed. The experimental results were compared with the Model Code 2010 predictions. It was revealed that the code overestimates the cracking load by 65-90%, and it is most likely due to the neglect of the shrinkage effect. It has been shown that 30-45% of the strain increment due to the long-term loading occurred during the first two-three days. The deformations of RC ties have practically stabilized after almost 300 days. The code quite accurately predicted the ultimate long-term strains. However, the prediction model was found to be too simplified to assess the increment of the long-term deformations. INTRODUCTION Structures are designed to satisfy both strength and serviceability requirements. In consequence of the extensive studies, the ultimate load behavior of reinforced concrete (RC) flexural members is well understood. Nevertheless, due to the use of refined ultimate state theories as well as higher strength materials, resulting in structures with longer spans and smaller depths, control of deformations is often the governing design criterion. Adequate modelling of cracking and, particularly, post-cracking behavior, as one of the major sources of physical nonlinearity, is the most important and difficult task of structural mechanics. Complex physical phenomena, such as concrete creep, shrinkage, and cracking greatly contribute to deformation increments: the long-term deformations might increase up to 3-4 times above the initial values (Gribniak et al. 2013). Most of the studies of the long-term deformations of RC members were dedicated to the investigation of bending members and only a few experimental programs were devoted to RC ties (Jaccoud 1987, Beeby and Scott 2005, Wu and Gilbert 2008, Vilanova et al. 2014). To fill this gap, the current study reports experimental results of four RC ties tested under short-term and under sustained load for a period of 315 days. The results gathered from the short-term experiments were compared to the deformations predicted by the Model Code 2010. CONCREEP 10 958