This paper investigates the restraint of imposed strains in edge restrained members and in particular, experimentally illustrates the influence of vertical steel reinforcement between the restrained (wall) and the restraining (base) member on the mechanism of restraint development. The investigation constructed real scale reinforced concrete walls onto reinforced concrete bases and also illustrated why previous studies, which have mostly utilized steel members to restrain the imposed strain, are inappropriate for gaining an understanding of edge restraint as they fail to reflect the heat transfer between the wall and the base. Results revealed that the restraint increased in the presence of vertical steel reinforcement from 0.37 to 0.72. They also showed that restraint increases with time due to the steel reinforcement and decreases in its absence. A finite element analysis of the walls is also presented to highlight the significance of correctly incorporating the real time boundary conditions.

Excessive cracking due to restraint of thermal and shrinkage strains is a widespread problem in the concrete construction industry. In design, restraint induced cracking is managed by the provision of reinforcement intended to distribute internal strains in such a way as to control the cracking pattern and limit crack widths. The area of secondary (horizontal) reinforcement required in members such as retaining walls and water tanks is often governed by the need to control early age thermal cracking. This paper presents results from four edge restrained walls tested at Imperial College London and the University of Leeds as part of an Engineering and Physical Sciences Research Council funded project into restraint induced cracking. The paper describes the development of volumetric strain and cracking in the tested walls. The cracking performance is assessed by comparing the restrained strain with the tensile strain capacity of concrete.degree of restraint, early age, edge restraint, imposed strain, thermal strain 1 | BACKGROUND | IntroductionConcrete structures undergo early age as well as longterm (LT) volumetric changes due to several actions including early-age thermal (EAT) strains and LT shrinkage strains. 1 If these strains are restrained either internally (by reinforcement or another part of the same cross section) or externally by adjoining members, stresses develop in the concrete with a magnitude proportional to the restrained strain. This phenomenon can lead to cracking if the stress levels exceed the tensile strength of the concrete. 2 Little experimental work has been carried out to investigate cracking in edge restrained members which are the subject of this paper. Stoffers 3 examined the influence of reinforcement ratio, wall aspect ratio and presence or absence of wall curvature in 18 tests of reduced scale micro-concrete walls with cross section of 60 Â 375 mm 2 . The maximum reinforcement diameter was 3 mm. Kheder et al. 4 examined the influence of wall aspect ratio. They tested 14 reduced-scale mortar walls Discussion on this paper must be submitted within two months of the print publication. The discussion will then be published in print, along with the authors' closure, if any, approximately nine months after the print publication.

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Major factors contributing to the shear behavior in reinforced concrete (RC) beams have been identified as compressive strength of concrete, shear span to effective depth ratio, and longitudinal reinforcement. Though significant, few of these factors are not fully incorporated in ACI code provisions for design of minimum shear reinforcement. To investigate the effect of these parameters, an analytical and experimental study was undertaken on the shear behavior of ordinary strength RC slender beams with moderate longitudinal reinforcement. The experimental program consisted of testing of eight simply supported RC slender beams subjected to two concentrated loads at a shear span to depth ratio (a/d) of 2.5 and equipped with varying shear reinforcement according to four different criteria. Ultimate shear strengths obtained in this experimental program are compared to the analytical shear strengths calculated according to existing as well as proposed equations. Test results exhibit that, the modified equation proposed in this work gives more accurate prediction of shear capacity of RC beams.