Research Article Experimental and Numerical Evaluation of Direct Tension Test for Cylindrical Concrete Specimens Jung J. Kim 1 and Mahmoud Reda Taha 2 1 School of Architecture, Kyungnam University, Changwon-si 631-701, Republic of Korea 2 Department of Civil Engineering, University of New Mexico, Albuquerque, NM 87131, USA Correspondence should be addressed to Mahmoud Reda Taha; mrtaha@unm.edu Received 14 April 2014; Accepted 22 May 2014; Published 19 June 2014 Academic Editor: Serji N. Amirkhanian Copyright © 2014 J. J. Kim and M. Reda Taha. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Concrete cracking strength can be deined as the tensile strength of concrete subjected to pure tension stress. However, as it is diicult to apply direct tension load to concrete specimens, concrete cracking is usually quantiied by the modulus of rupture for lexural members. In this study, a new direct tension test setup for cylindrical specimens (101.6 mm in diameter and 203.2 mm in height) similar to those used in compression test is developed. Double steel plates are used to obtain uniform stress distributions. Finite element analysis for the proposed test setup is conducted. he uniformity of the stress distribution along the cylindrical specimen is examined and compared with rectangular cross section. Fuzzy image pattern recognition method is used to assess stress uniformity along the specimen. Moreover, the probability of cracking at diferent locations along the specimen is evaluated using probabilistic inite element analysis. he experimental and numerical results of the cracking location showed that gravity efect on fresh concrete during setting time might afect the distribution of concrete cracking strength along the height of the structural elements. 1. Introduction Concrete cracking strength is diicult to be quantiied and therefore is a source of considerable uncertainty in ser- viceability prediction. he existence of cracks under service load in reinforced concrete (RC) structures makes it diicult to predict delections. While cracked concrete is usually assumed to be incapable of carrying tensile stresses, the concrete between adjacent cracks can resist tensile force due to the bond between concrete and steel reinforcement. his is known as tension stifening efect. herefore, for the consid- eration of the delections of RC structures, concrete cracking strength afects the structural stifness of the members. Moreover, cracking plays an important role in the durability of RC structures. When concrete cracks, its permeability increases and the processes of concrete deterioration and rebar corrosion get accelerated [1, 2]. For lexural elements, concrete cracking is usually repre- sented by the modulus of rupture [3]. However, in research experiments, the modulus of rupture showed a wide vari- ation [4, 5]. While the modulus of rupture provides a good estimate for cracking strength, researchers showed that accurate serviceability predictions require obtaining the real tensile strength of concrete [6]. Moreover, researchers have argued that, because of the signiicance of shrinkage on serviceability of RC structures, other cracking criteria, such as the direct or indirect tensile strength of concrete, should be used as evidence of concrete cracking [7]. hree methods are commonly used to measure concrete cracking strength: lexural, splitting, and direct tension test. While the lexural strength test and splitting tensile strength test can be conducted in accordance with the American standard test method (ASTM), ASTM C 78 [8] and ASTM C 496/C 496M [9], respectively, ASTM has no recommendations for direct tension test for concrete, as it is challenging to ensure that uniaxial stress along the specimen is evenly applied. Several methods have been proposed for direct tension test, such as using friction grip, anchor, and epoxy, to attach Hindawi Publishing Corporation Advances in Civil Engineering Volume 2014, Article ID 156926, 8 pages http://dx.doi.org/10.1155/2014/156926