International Concrete Abstracts Portal

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.

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.

The analysis of the response of building structures to dynamic loads is a difficult task, especially if the response is nonlinear, as in the case of concrete buildings subjected to strong seismic ground shaking. This is one of the most difficult tasks facing the structural engineer. The methods available for linear elastic analysis are summarized briefly, together with comments on the development of proper mathematical models for such analysis. A discussion of the main techniques suitable for the inelastic analysis of concrete buildings follows, again accompanied by practical guidelines for mathematical modeling for such analyses. The last section provides a list of several computer programs for engineers contemplating inelastic analyses of concrete buildings.

A brief discussion of soil-structure interaction, particularly in terms of its effects on structures subjected to earthquakes, is presented. Factors influencing the degree to which soil-structure interaction modifies the response of structures, when compared to the response of rigid-based structures, are listed. The distinction between inertial and kinematic components of soil-structure interaction is made and the generally beneficial effects of interaction on earthquake structural response is noted. Soil-structures interaction effects are most pronounced in rigid, massive structures founded on compliant soils. Brief mention is made of the uncertainties surrounding the determination of interaction effects on structural response, especially those associated with the effects of nonlinear soil behavior.

Inelastic static and dynamic analysis of reinforced concrete structures is demonstrated with a specific example taken from the U.S.-Japan Cooperative Program on Earthquake Engineering. The analytical process is explained from a hierarchical perspective, starting with material constitutive relationships, progressing to cross-sectional and element modeling, and culminating with the assembly of the complete system. The computed static and dynamic inelastic response of the mathematical model is than compared to the behavior observed during shaking table tests of the 1/5-scale laboratory model. The paper concludes with a detailed discussion of the degree of correlation obtained, and suggestions for future coordinated analytical-experimental research.