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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 15 Abstracts search results
October 1, 1991
Deformation capacity of reinforced concrete columns is investigated by examining the available test data. Tests of square columns, conducted under constant axial load and lateral displacement reversals, as well as those conducted under concentric compression, are considered. The test data are evaluated in terms of ductility and drift ratios. The results indicate that high axial compression, and high shear stress reversals, as well as high rates of loading, reduce column deformability. Confinement of core concrete improves column deformability significantly. This is achieved through the use of closely spaced transverse and longitudinal reinforcement, where the longitudinal reinforcement is laterally supported by closed hoops and crossties. The confinement action also improves with the volumetric ratio and yield strength of transverse reinforcement. The ACI 318-89 requirements for the amount of confinement reinforcement appear to be adequate for the columns evaluated in this paper.
Characteristic features of reinforced concrete response relevant to hysteretic modeling are discussed. The relationships between hysteretic features, and design and detailing parameters are illustrated. Experimentally obtained hysteretic force-deformation relationships are used to demonstrate the significance of each hysteretic feature on modeling. A brief review of selected hysteretic models is presented, Strength, as defined by primary curve, stiffness degradation, strength decay, and pinching of hysteresis loops are discussed as basic features of hysteretic response. The mechanisms behind these features and related design and detailing parameters are presented. The significance of each of these parameters in terms of deformation components resulting from flexure, shear, and reinforcement extension/slip is discussed. The dominant response shows stable hysteretic loops with little or no strength decay within the realistic range of deformations. Therefore, a simple hysteretic model may be appropriate for modeling flexural response. Shear response as well as hysteresis loops resulting from reinforcement slippage show pinching action, and hence should be modeled accordingly. Axial compression, lack of shear/confinement reinforcement, and poor anchorage of members may lead to early and rapid strength decay. Strength decay may have to be considered in such members. Stiffness degradation during unloading and reloading is a characteristic feature of reinforced concrete response, and should be considered in modeling all deformation components.
Mark Fintel and S. K. Ghosh
An alternative to the empirical code approach for earthquake-resistant design of building structures is proposed. The suggested procedure uses carefully selected earthquake accelerograms as loading and dynamic inelastic response history analysis to determine member forces and deformations. A number of analyses make it possible to design into the structural elements a desirable balance between flexural strength, shear capacity, and ductility. The amount of allowable ductility in a yielding member depends on selected serviceability criteria and on the deformational capacity of the member. The design approach makes it possible to predetermine the sequence in which inelasticity spreads to various designated structural members. A structure needs to be provided with special ductility details only in the predetermined hinging regions.
Daniel P. Abrams
This chapter serves as a primer to acquaint a novice with the vast amount of experimental data that has been acquired over the last two decades on behavior of reinforced concrete components subjected to repeated reversals of lateral force and earthquake response of concrete building systems. General characteristics of hysteretic behavior and dynamic response are presented rather than discrete summaries of each test program done to date. An extensive reference list presents over 400 publications that specifically address laboratory studies of reinforced concrete members, joints, or building systems. The listing is subdivided for laboratory investigations of (a) beams and beam-column joints, (b) columns, (c) walls, (d) frame and frame-wall systems, (e) coupled-wall systems, and (f) infilled-frame systems.
Catherine Wolfgram French and Arturo E/ Schultz
In an effort to provide the structural design profession with an indication of the deformation capacity of reinforced concrete beams subjected to cyclic loading, results of 69 isolated reinforced concrete beam tests were assembled and interpreted. The influence of several parameters, including longitudinal reinforcement ratio, web reinforcement ratio, shear stress, shear span-to-depth ratio, axial load, floor slabs, loading rate, and loading history on deformation capacity were investigated. It was found that ductility factors in the range of two to nine reasonably may be expected from reinforced concrete beams. Of the parameters investigated, shear was identified as the single most important factor affecting deformation capacity. It was further determined that the effects of shear can be controlled most directly by limiting the demand placed on web reinforcement. To insure that beams exhibit ductility factors of at least five, it is recommended that the maximum shear force demand on web reinforcement be limited to 60 percent of its nominal capacity.
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