Shrinkage effect on short-term deformation behavior of reinforced concrete – When it should not be neglected Viktor Gribniak ⇑ , Gintaris Kaklauskas, Romualdas Kliukas, Ronaldas Jakubovskis Vilnius Gediminas Technical University, Sauletekio av. 11, Vilnius LT-10223, Lithuania article info Article history: Received 17 March 2013 Accepted 10 May 2013 Available online 21 May 2013 Keywords: Concrete Shrinkage Design abstract Traditionally, concrete shrinkage along with cracking provides one of the major concerns to the designers because of the inaccuracies and unknowns that surround them. Although shrinkage is mainly associated with long-term effects, even at first loading, restrained shrinkage may cause cracking of concrete. The essential point of present study is to specify the cases of short-term deformation analysis of reinforced concrete (RC) structures when the shrinkage effect should not be neglected. The study combines the knowledge on material and structural aspects of shrinkage phenomenon. The manuscript considers phys- ical nature of shrinkage pointing out the major means of reducing shrinkage deformations. The article also discusses peculiarities of constitutive modeling of shrunk reinforced concrete members and gives recommendations for improving adequacy of the design. Furthermore, the paper discusses application of steel fibers as an efficient additive to reduce adverse effects of restrained shrinkage. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Increasing application of high-strength materials resulted in longer spans and reduced stiffness of structural elements with deformations frequently being the governing criterion in the de- sign [1,2]. External loads, environmental actions, and deleterious reactions may cause tensile stresses in structural elements. The combination of high tensile stresses with low fracture resistance of concrete often results in cracking that reduces the durability of concrete structures. Restraining of concrete shrinkage is another important, although most frequently neglected effect related to cracking and deformations of reinforced concrete (RC) structures. In general practice, shrinkage along with creep is taken into ac- count in pre-stress loss and/or long-term deformation analysis. However, even at first loading, free shrinkage strain of concrete may be of a magnitude well exceeding the cracking strain. Due to the restraining action of reinforcement (or peculiarities of the structural system), shrinkage induces tension stresses in the con- crete that might significantly reduce the crack resistance and in- crease deformations of RC members. Most usually this effect is not taken into account, thus, the short-term deformation and crack width predictions as well as results of the constitutive modeling may be misinterpreted. The necessity to assess shrinkage influence on deformation behavior of cracked RC members has been recognized from the beginning of the second half of 20th century by Lash [3], Scanlon [4], and other researchers who had conducted comprehensive experimental studies on deformation behavior of RC. Since the first attempts to assess the shrinkage effect on the design of RC struc- tures, the investigations were mainly performed in two separate ways. From the one hand, shrinkage was considered as a material property of concrete. Material scientists, prominent in concrete mixture composition, chemical additives, and their effects on shrinkage deformations [5–8], often ignored structural problems. From the other hand, the structural studies, recognizing impor- tance of the shrinkage effect on structural behavior, were focused on deduction of empirical equations nominally limited to simple cases of cracking and deformation analysis of RC elements sub- jected to tension [9,10] or flexure [11,12]. For decades, development of numerical tools has resulted in ex- tended application of computers in structural design. However, calculation results are always dependent on the assumed material laws. Application of inadequate constitutive models may cause sig- nificant errors in design of RC structures. Until nowadays, concrete shrinkage along with cracking provides one of the major concerns to the designers because of the inaccuracies and unknowns that surround them. To prevent the deleterious outcomes, an engineer should, at least, recognize importance of the restrained shrinkage effect on the structural behavior. In this respect, only a few inves- tigations [13,14] can be mentioned. Using the test results [15–17] in combination with an innova- tive numerical procedure [18], the authors have proposed a novel 0261-3069/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.matdes.2013.05.028 ⇑ Corresponding author. Tel.: +370 6 134 6759; fax: +370 5 270 0112. E-mail addresses: Viktor.Gribniak@vgtu.lt (V. Gribniak), Gintaris.Kaklaus- kas@vgtu.lt (G. Kaklauskas), Romualdas.Kliukas@vgtu.lt (R. Kliukas), Ronaldas.Ja- kubovskis@vgtu.lt (R. Jakubovskis). Materials and Design 51 (2013) 1060–1070 Contents lists available at SciVerse ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes