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International Concrete Abstracts Portal

Showing 1-5 of 19 Abstracts search results

Document: 

SP205-01

Date: 

January 1, 2002

Author(s):

F. J. Vecchio and D. Palermo

Publication:

Symposium Papers

Volume:

205

Abstract:

A critical look is taken at the state-of-the-art in nonlinear finite element analysis of reinforced concrete structures. In examining the results of recent prediction competitions, the accuracy of such analysis procedures is gauged. Reasons for caution when applying nonlinear analysis methods are then identified and discussed. Finally, the results of a test program involving shear critical beams are presented in support of the contention that the behaviour of reinforced concrete is still not well understood. The tests represent a good challenge for validating current procedures.

DOI:

10.14359/11630


Document: 

SP205-14

Date: 

January 1, 2002

Author(s):

H. Nakamura and T. Higai

Publication:

Symposium Papers

Volume:

205

Abstract:

The buckling of reinforcing bars is investigated analytically and several indices which characterize the buckling behavior are introduced based on the analytical results. In this paper, buckling analysis of the reinforcing bars is performed by the finite element method using large deflection theory of layered beam elements. The buckling behavior is considered under monotonic and cyclic loading. Based on the analytical results, several indices such as the buckling stress, the residual stress and the buckling mode are used to characterize the buckling behavior. Considering these results, a stress-average strain relationship of the reinforcing bars is developed accounting for inelastic buckling. The model features a post-buckling softening branch, since the buckling behavior is considered in the form of a material property, which is an easy method to introduce the effect of buckling in the finite element method.

DOI:

10.14359/11644


Document: 

SP205-15

Date: 

January 1, 2002

Author(s):

M. Y. Mansour, T. T. C. Hsu, and J. Y. lee

Publication:

Symposium Papers

Volume:

205

Abstract:

The load-deformation response of R/C membrane elements (panels) subjected to reversed cyclic shear showed that the orientation of the steel bars with respect to the principal coordinate of the applied stresses has a strong effect on the pinching effect in the post-yield hysteretic loops. When the steel bars were oriented in the directions of the applied principal stresses, there was no pinching effect. When the steel bars were oriented at an angle of 45’ to the applied principal stresses, there was severe pinching effect. It was obvious that the pinching effect is caused by the orientation of the steel bars, rather than the bond slips between the steel bars and the concrete as surmised by many researchers. A non-linear analytical model capable of describing this pinching behavior is presented in this paper. The model is actually an extension of the fixed-angle softened truss model (FA-STM) proposed by Hsu and his colleagues for monotonic loading. The extension of FA-STM for application to reversed cyclic loading requires new constitutive models for concrete and steel in the unloading and reloading ranges. This rational theory satisfies Navier’s three principles of the mechanics of materials: equilibrium, compatibility and constitutive relationships of materials. The validity of this theory is illustrated by comparing the behavior of three panels with three different steel bar angles. The predicted cyclic behavior compared well with the experimental behavior, except in the descending branch.

DOI:

10.14359/11645


Document: 

SP205-06

Date: 

January 1, 2002

Author(s):

S. Saito and T. Higai

Publication:

Symposium Papers

Volume:

205

Abstract:

A computationally efftcient procedure is presented for analyzing the performance of reinforced concrete structures under cyclic loading. A rigid-body-spring network is used as a basis of a material representation. Concrete is modeled as an assemblage of discrete particles interconnected along their boundaries through flexible interfaces. Random geometry is introduced using Voronoi diagrams in order to reduce mesh bias on crack propagation. Rather than averaging the effects of reinforcing over a regional material volume, rein-forcing bars are explicitly modeled using line elements with nonlinear linkage springs. The spring network has the advantage to model material discontinuities and provides realistic predictions of concrete cracking. The network performance is demonstrated through analyses of reinforced concrete columns under cyclic loading. Numerical results reasonably agree with experimental observations in terms of load carrying capacity and crack propagation. Deterioration of load carrying capacity due to shear failure after or before yielding of main reinforcing steel is discussed through the numerical predictions.

DOI:

10.14359/11636


Document: 

SP205-07

Date: 

January 1, 2002

Author(s):

R. K. Dowell and D. R. Parker

Publication:

Symposium Papers

Volume:

205

Abstract:

Finite element analyses were conducted of as-built and seismically retrofitted RC bridge columns tested at UCSD. The as-built columns were provided with the same rectangular cross section and shear reinforcement, resulting in approximately the same shear capacity, but were designed to fail at different levels of ductility in either a brittle or flexural shear failure. This was accomplished by adjusting the shear force demand by varying the column height (or aspect ratio) and the grade of longitudinal reinforcement. In the analysis the challenge was to capture the overall force-deformation hysteretic behavior and failure mechanism, as well as the individual deformation components of flexure and shear. The analysis focuses on the shear behavior of concrete under large tensile strains and calibrates the shear stress capacity to the concrete component of the UCSD shear model, which reduces as a function of curvature ductility at the critical section. Also, the shear modulus is reduced in proportion to the ratio of cracked to gross flexural stiffness. The results show that a relatively simple design oriented shear capacity model can be used to calibrate the required shear parameters of the 3-D plasticity concrete model. In the paper, detailed finite element analyses are conducted to assess the shear force capacity and post-peak deformation response of shear dominated RC bridge columns.

DOI:

10.14359/11637


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