Research Activities

IDARC2D, Version 4.0 Now Available

by A. Reinhorn

Version 4.0 of IDARC2D, the Inelastic Damage Analysis of Reinforced Concrete computer program, is now available. The new release of IDARC2D incorporates the results from recent experimental testing on reinforced concrete components and structures, as well as structural steel elements. Results from the test programs have led to enhancements in modeling using macromodels with new distributed plasticity models, new hysteretic models, and modification of the combined model for shear-flexure capacity of members. As a result, IDARC2D can capture the response of reinforced concrete and structural steel elements more accurately.

In parallel with an experimental program to study the response of buildings with damper elements for seismic protection, new mathematical models for such elements were developed, incorporated and verified in the program. IDARC2D is now capable of accurately predicting the response of inelastic multistory buildings with fluid or solid viscoelastic, friction and hysteretic damper elements.

In conjunction with a loss assessment program in a metropolitan area in the vicinity of the New Madrid Seismic Zone and an experimental program, a model for masonry infill panel elements was incorporated and tested. This model may be used to study the response of masonry infill buildings, which are commonly found as low- to medium-rise structures in metropolitan areas. IDARC2D can be used to model buildings with masonry walls, or other type of infill panels.

Following the need for seismic evaluation proposed in ATC-33 (1995) using the results from lateral pushover analysis, monotonic inelastic analysis was refined and incorporated. An extended and more realistic set of options to carry out the pushover analysis have been developed and incorporated. Furthermore, the need to better characterize the structural performance of a building during a seismic event led to an analytical investigation to develop a damage model from basic physical considerations. The new model, referred to as a fatigue based damage model, developed by Reinhorn and Valles (1996), was incorporated in the program, along with a global damage model, and the model by Park and Ang (1984) that was introduced in the first release of IDARC, and is now a benchmark damage quantification index. IDARC2D offers a broader range of pushover and damage indices derived from strong physical considerations.

Finally, most program routines, internal variables and program structure were checked and optimized to improve performance and reduce execution time. The users manual was revised and restructured to facilitate input data preparation. IDARC2D is now more efficient and user friendly.

IDARC2D was developed for use on the VAX, SUN or PC/DOS operating systems. Program distribution and technical information is available on the World Wide Web at

Also, an NCEER technical report is currently being prepared, entitled

IDARC2D Version 4.0: A Computer Program for the Inelastic Damage Analysis of Buildings, NCEER-96-0010,

which will be available this summer. Its publication will be announced in the NCEER Bulletin and on the web site.

A users group has been established for IDARC. Members of the users group are entitled to the latest version of the program and future updates. For more information on the users group, consult the WWW home page or contact:

Dr. Andrei M. Reinhorn
University at Buffalo
phone: (716) 645-2114, ext. 2419


Dr. Sashi K. Kunnath
University of Central Florida
phone: (407) 823-0176


Applied Technology Council, (1995), "Guidelines and Commentary for the Seismic Rehabilitation of Buildings," Three Volumes, ATC-33.02, 50% Submittal, Second Draft, FEMA.

Park, Y.J., Ang, A.H.-S. and Wen, Y.K., (1984), "Seismic Damage Analysis and Damage-Limiting Design of R/C Buildings," Civil Engineering Studies, Technical Report No. SRS 516, University of Illinois, Urbana.

Valles, R.E., Reinhorn, A.M. and Barron, R., (1996), "Seismic Evaluation of a Low-Rise RC Building in the Vicinity of the New Madrid Seismic Zone," Technical Report NCEER-96-xxxx, National Center for Earthquake Engineering Research, State University of New York at Buffalo (in review).

Valles, R.E., Reinhorn, A.M., Kunnath, S.K., Li, C., and Madan, A., (1996), "IDARC2D Version 4.0: A Computer Program for the Inelastic Damage Analysis of Buildings," Technical Report NCEER-96-0010, National Center for Earthquake Engineering Research, State University of New York at Buffalo.

Some of the material reported herein is based upon work supported in whole or in part by the National Science Foundation, the State of New York, the U.S. Department of Transportation, the Federal Highway Administration, the Federal Emergency Management Agency and other sponsors. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of NCEER or its sponsors.

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