for Reinforced Concrete Wall Buildings

BTM-shell Methodology in the Program FE-MultiPhys


Note: One of the winners of the PEER's blind prediction contest was Professor S. Girgin who used the nonlinear cyclic truss model of Moharrami et al. (2014). (contest results)


The Online School in collaboration with Professor Ioannis Koutromanos (Virginia Tech), presents a new computational framework that enables the advanced and practical analysis of reinforced concrete structural wall (RCSW) components and building systems. Compared with analysis methods used in current performance-based seismic design (PBSD) and retrofit practice in U.S., this framework results in two major advancements:  the accurate computation of various severe damage and failure modes of RCSWs and building systems that consider the nonlinear behavior of all structural components. The methodology uses the new BTM-shell element, based on the beam-truss-model (BTM), and the new finite-element program FE-MultiPhys that enables nonlinear (material and geometry) static and dynamic analysis as well as parallel processing (multi-threaded) for the efficient analysis of large (entire buildings) fully-nonlinear models. The program is compatible with the graphical pre- and post-processor LS-PrePost. The BTM has been extensively validated based on experimental testing results of reinforced (RC) walls, columns, beams, and slabs under cyclic static and dynamic load, and computes accurately various critical damage and failure modes of RC walls. The computational efficiency of the BTM for large structural systems was demonstrated in the 2010 Chile M8.8 earthquake collapse simulation of the Alto Rio building (281K nonlinear elements).

The BTM-shell is enhanced here using a recently published material model for cyclic behavior of  reinforcing steel that enables efficient computation of bar buckling and rupture, as well as by considering the nonlinear out-of-plane shear behavior. The computational framework is validated using five case studies. Case Studies A to C analyze barbel, C-shape, and rectangular walls, respectively, that experienced the following failure modes during testing: (A) diagonal shear (tension); (B) diagonal crushing; and (C) out-of-plane plastic hinge buckling. Case Study D models the mixed bar buckling shear failure of the largest special moment frame RC beam that has been tested in U.S. Finally, Case Study E presents the nonlinear response history analysis for a Los Angeles-MCE-level ground motion of a 20-story RC-core wall building that models the nonlinear material behavior of 8480 elements of all components (walls, slabs, beams, and columns).


This web page includes a report and User’s Manual, providing detailed information, examples, on all input definitions (elements, materials, solvers, etc.) as well as on pre- and post-processing together with 4.5 hours of video tutorials on the use of the computational framework.

Publications on Truss and Beam-Truss-Model (BTM)

  1. Alvarez R., Restrepo JI, Panagiotou M (2019). Nonlinear Cyclic Beam Truss Model for Analysis of Reinforced Concrete Coupled Structural Walls, Bull. Earthq. Eng., 17(11),

  2. Alvarez R., Restrepo JI, Panagiotou M, Godinez S (2020a). Analysis of Reinforced Concrete Coupled Structural Walls Via the Beam-Truss Model, Engineering Structures. Link

  3. Alvarez R., Restrepo JI, Panagiotou M. (2020b). Plastic Hinge Out-of-Plane Buckling in Structural Walls - Analysis Using the Beam-Truss Model, ASCE, J. Struct. Eng., in press.

  4. Deng X., Koutromanos I., Murcia-Delso J., Panagiotou M. (2021). Nonlinear Truss Models for Strain-based Seismic Evaluation of Planar RC Walls. Earthquake Engineering and Structural Dynamics. Link

  5. Lu Y, Panagiotou M (2015). Earthquake Damage Resistant Tall Buildings at Near Fault Regions Using Base Isolation and Rocking Core Walls. Proceedings, Structures Congress, Portland, OR. Link

  6. Lu Y, Panagiotou M. (2014). Three-Dimensional Nonlinear Cyclic Beam-Truss Model for Reinforced Concrete Non-Planar Walls. ASCE, J. Struct. Eng., 140(3),

  7. Lu Y, Panagiotou M, Koutromanos I (2014). Three-Dimensional Beam-Truss Model for RC Walls and Slabs Subjected to Cyclic Static or Dynamic Loading. PEER Report No. 2014/18, Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA.

  8. Lu. Y, Panagiotou M, and Koutromanos I. (2016). “Three-dimensional beam-truss model for RC walls and slabs, Part I: Model Description and Validation for Individual Walls. Earthq.Eng. Struct. Dyn., 45(4): 1495–1513,

  9. Lu Y, Panagiotou M (2016). Three-Dimensional Beam-Truss Model for RC Walls and Slabs, Part II: Model Description and Validation for Coupled Walls and Slabs. Earthq.Eng. Struct. Dyn., 45(11): 1707–1724,

  10. Mavros M, Panagiotou M, Koutromanos I, Alvarez R, Restrepo JI. (2022). Seismic analysis of a modern 14-story reinforced concrete core wall building system using the BTM-shell methodology. Earthquake Engng Struct Dyn.  Free access link

  11. Moharrami M, Koutromanos I, Panagiotou ., Girgin SC (2014). Analysis of Shear-Dominated RC Columns Using the Nonlinear Truss Analogy. Earthq. Eng. Struct. Dyn., 44(5): 677–694,

  12. Moharrami M., Koutromanos I., Panagiotou M. (2015). Nonlinear Truss Modeling Method for the Analysis of Shear Failures in Reinforced Concrete and Masonry Structures. Proceedings, ATC&SEI 2nd Conference on Improving the Seismic Performance of Existing Buildings and Other Structures, December, San Francisco. CA.

  13. Panagiotou M., Restrepo JI, Schoettler M, Geonwoo K (2012). Nonlinear Truss Model for Reinforced Concrete Walls. ACI Struct. J., 109(2): 205–214.

  14. Panagiotou M., Koutromanos I., Mavros M., Deng X., Alvarez R., Restrepo J.I., Murcia-Delso J., Acero G. (2021). Nonlinear Beam-Truss Model (BTM) for Seismic Performance Evaluation of Reinforced Concrete Wall Buildings. 2021 SEAOC Convention Proceedings, San Diego, California.

  15. Zhang P, Restrepo JI, Conte JP, Ou J. (2017). Nonlinear Finite Element Modeling and Response Analysis of the Collapsed Alto Rio Building in the 2010 Chile Maule Earthquake. Struct. Des. Tall Spec. Build., 207;26. doi:10.1002/tal.1364.