International Concrete Abstracts Portal

SP-237CD This CD-ROM is a collection of 19 papers presented at a workshop sponsored by Joint ACI-ASCE Committee 447, Finite Element Analysis of Reinforced Concrete Structures, and JCI Committee 016SP, in Maui, Hawaii, USA, in November 2003. A broad range of topics was addressed, including the creation of new experimental data sets for use in developing, calibrating, and validating models; the development and validation of plain, reinforced, and fiber-reinforced concrete constitutive models; new approaches to simulating the response of reinforced concrete continua; new element formations to enable improved simulation of component response; and new computational techniques.

Seismic design provisions for beam-column joints in the AIJ guidelines are based mainly on earlier experimental studies. However, it is necessary to establish a more rational, performance-based design method, especially for joints subjected to two directional seismic forces. This can be accomplished by analytical study of the stress transfer mechanisms in joints. In order to understand the progression of damage in joint concrete, accumulated absorbed strain energy for concrete and reinforcement was calculated from the results of FEM analysis. The stress transfer mechanisms and progression of damage in concrete and reinforcement provide a basis for establishing a more rational, performance-based design method for RC structures.

Damage assessment has become more important than ever since structural designers started to employ performance based design methods, which require structural and member behaviors at different limit states be predicted precisely. This study aims to clarify the confining effect of concrete of a plastic hinge zone of a reinforced concrete column confined by shear reinforcement, so that a designer can accurately predict damage when columns experience seismic loadings that includes large axial force and bilateral deformations. In an experimental program, eight half-scale columns and eight full-scale columns were tested under the reversal bilateral displacement with constant or varying axial load in order to study the effects of loading history and intensity on the confining effect. Since shear failure was inhibited by providing enough transverse reinforcement, as defined by the previous Japanese design guidelines, damage gradually progressed in a flexural mode with concrete crushing and yielding of reinforcing bars. The damage level depended on the bilateral loading paths and the axial load history. In an analytical program, a section analysis using a fiber model was employed and the effect of confinement on the behavior of core concrete was studied. The analysis predicted the observed deterioration of moment capacity and longitudinal shortening under different loading conditions and for different specimen sizes. The study is considered to increase the accuracy with which damage in reinforced concrete columns subjected to severe loading is assessed.

A Cyclic Softened Membrane Model (CSMM) was developed to rationally predict the cyclic shear responses of reinforced concrete (RC) elements, including the pinching effect in the hysteretic loops, the shear stiffness, the shear ductility and the energy dissipation capacities1, 2. This CSMM model was verified by the tests of fifteen RC panels at the University of Houston. Test results confirmed that the orientation of the steel bars and the percentage of steel in a panel are the two most important variables that influence the cyclic response of RC panel elements.Using OpenSees as a framework, the concept of the CSMM was simplified from a 2-D model into a 1-D model and implemented into a finite fiber element program for the prediction of concrete frame structures subjected to cyclic or dynamic loading. The developed program is validated by the reversed cyclic load tests of a reinforced concrete column and by the shake table tests of a prestressed concrete frame. The CSMM has recently been implemented into an OpenSees-based finite element program for a 2-D RC element that will allow structural engineers to predict the monotonic, cyclic and dynamic responses of structures containing walls. This 2-D RC element is validated in this paper by the prediction of the monotonic responses of two RC panels subjected to shear stresses.

The purpose of this paper is the development of simplified numerical tools dedicated to seismic analysis of reinforced concrete structures. Beam formulation and constitutive relationships are described to simulate the behavior of shear walls under complex loadings. The attention of this work focuses on the torsion effects and the way to account for cross section wraping for simplified analysis.