International Concrete Abstracts Portal

SP12 Contains the proceedings of the 1964 International Symposium on Flexural Mechanics of Reinforced Concrete. In addition to providing a more basic understanding of the complex, non-ideal flexural behavior of reinforced concrete, this publication aims to further both immediate and long-range objectives in improving the analytical and statistical basis for the flexural design of reinforced concrete.

With discussion by Chan W. Yu and M. T. Soliman, and Alan H. Mattock. Limit design theories for reinforced concrete statically indeterminate structures require a knowledge of the rotational capacity of hinging regions in reinforced concrete members. An investigation is reported of this rotational capacity in reinforced concrete beams. Thirty-seven beams were tested involving the following variables: concrete strength, depth of beam, distance from point of maximum moment to point of zero moment, and amount and yield point of reinforcement. The data are analyzed and a method is proposed whereby the rotational capacity of a hinging region in a reinforced concrete beam may be calculated.

With discussion by E. Burnett, D. B. Beal, R. H. Wood, and A. L. L. Baker. The moment-rotation results are presented of tests on beams carried out by a number of laboratories working under the auspices of the European Concrete Committee. Idealized diagrams are plotted for comparison, and the basis of these diagrams is given as defining fundamental moment curvature relationships which may be used in ultimate load calculations of frameworks. A simple trial and adjustment method of design is explained in which compatibility of bending moment values and end-slopes can be established by joint by joint procedure. Simplification is effected by separating the sway angle from the total rotation at hinges. This simplification can either be made by joint trial and adjustment procedure or by using the Miiller-Breslau compatibility equations, separating the sway angle, which greatly simplifies these equations.

With discussion by P. R. Barnard, S. Stockl, Vitelmo Bertero and C. Felippa, and H. E. H. Roy and Mete A. Sozen. In the application of limit design to reinforced concrete structures, it is essential to know the rotation capacity of the connections. The rotation capacity seldom limits complete moment redistribution in moderately reinforced members subjected to transverse loads. However, it may prove to be a limitation for overreinforced members or members subjected to combined axial and transverse loads. Usually the rotation capacity of the section is governed by the ductility of the concrete which can be improved with the use of transverse reinforcement. This paper reports and discusses the effect of rectangular ties on the load-deformation characteristics of concrete.

With discussion by Kurt H. Gerstle and Leonard G. Tulin, and Hiroyuki Aoyama. The objective of this investigation was to establish moment-curvature relationships of reinforced concrete members subjected to constant axial load and reversal of bending. Both the theoretical and experimental approaches have been made, guided by the results of previous experimental investigations. A method of analysis was developed, based on three assumptions: a linear strain distribution over the section; elasto-plastic stress-strain relationship of steel neglecting the Bauschinger effect; elasto-plastic stress-strain relationship of concrete replacing the real curve and neglecting any stress in tension. The effects of variables were studied using this analysis. Reinforcement ratio and concrete strength had minor effects on the shape of momentcurvature diagram. The amount of axial load and the plastic deformation under the previous loading made drastic change. When the member had no axial load, the diagram had a shape like a parallelogram and larger the plastic deformation, the wider the diagram was in the horizontal direction. When the amount of axial load was small, the moment-curvature diagram had a step in the way of reversal, and the larger plastic deformation made this step larger. When the axial load was higher, this step became smaller and for even higher axial load it vanished completely, making a spindleshaped diagram. Tests were made on three reinforced concrete specimens, making all the measurements in the constant moment region of the specimen. The validity and limitation of theoretical analysis were checked. It was found that the agreement was almost perfect for initial loading and for the first reversal made slightly after the yielding in the initial loading. However, the agreement was not very good for reversals after the first reversal from a point considerably beyond the yielding. Study of this discrepancy indicated some modifications of the method of analysis.