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UCL Institute for Risk and Disaster Reduction


SLaMA Solver Frame: facilitating earthquake risk reduction with a computer app

By r.gentile@ucl.ac.uk, on 18 January 2022

Earthquake-induced direct and indirect losses tend to be high in highly populated earthquake-prone areas, especially in countries where most of the existing buildings and infrastructure are designed or built according to pre-seismic codes (if any). Therefore, there is a dire need to develop holistic strategies for mitigating and managing seismic risk. On the one hand, this involves risk understanding and quantification (e.g., risk/loss assessment methodologies). On the other hand, there is a crucial need to develop and implement strategies and techniques for repairing and retrofitting existing structures, which should be structurally effective, easy to apply, cost-effective, possibly reversible, and respectful of the architectural, heritage and cultural conservation requirements.

Both in the “diagnosis” and the “prognosis” phases, procedures to assess the structural performance under earthquake loads are paramount. Among many possibilities within the literature, choosing an appropriate assessment procedure depends on a simplicity vs accuracy trade-off governed by technical, economical, and time constraints. Moreover, various stakeholders have different needs on this matter: private owners likely need a detailed assessment focused on individual buildings or small portfolios, while government agencies or (re)insurance companies might look at large portfolios tolerating a lower refinement level and accepting higher uncertainties.

It is fundamental to select a procedure that can highlight the structural weaknesses of the considered structural system, so that it is possible to design retrofit solutions to specifically fix those. One procedure complying with this requirement, while being easy to apply, is SLaMA – Simple Lateral Mechanism Analysis.

Although SLaMA is normally applied using spreadsheets, it allows for defining the nonlinear force-displacement capacity and the sequence of local and global mechanisms of a building. It was introduced for the 1st time in the 2006 version of the New Zealand Society of Earthquake Engineering, NZSEE, Guidelines for the “Assessment and Improvement of the Performance of buildings in earthquakes” (NZSEE 2006), and revamped in the 2017 version (NZSEE 2017), after a substantial amount of research (Gentile 2017, Pampanin 2017; Del Vecchio et al. 2018; Gentile et al. 2019;  Gentile et al. 2019a; 2019b; 2019c; Bianchi et al. 2019). SLaMA is essentially mandatory in New Zealand, since it is required as an essential step before any other seismic numerical analysis is carried out. Its scope, however, is geographically much larger: more than 15 world-class companies (in New Zealand, Italy, Netherlands, UK) are using this method.

“SLaMA Solver Frame” is a free Windows/MacOS app created to enable engineers applying SLaMA using a graphical user interface, and without the need to create ad hoc spreadsheets. This app refers to reinforced concrete frame buildings, which constitute a substantial portion of the building stock in many countries around the world.

As shown in the tutorial video below, SLaMA Solver Frame is completely standalone (i.e., it does not require any other software to be run). It provides a “type and check” environment, in which every time the user inputs a parameter, the app automatically updates specific plots, therefore allowing for continuous cross checks and minimising input error. For each beam and column, SLaMA solver Frame provides their expected failure mode (flexure, bar buckling, shear, lap splice). For each beam column joint sub-assembly within the frame, the app determines its hierarchy of strength, indicating the member-level mechanism that causes its failure. Finally, by composing the results of each sub-assembly, SLaMA solver Frame provides an estimation of the plastic mechanism and the non-linear force-displacement curve.

SLaMA Solver Frame can be downloaded for free (for Windows and MacOS) at https://www.robertogentile.org/en/slamaf/. If you find any bugs, or you have any suggestions/comments, please feel free to report them dropping an email to robstructuralapps@gmail.com.

Disclaimer for SLaMA Solver Frame

SLaMA Solver Frame is provided by Dr Roberto Gentile under the Creative Commons “Attribution-No Derivatives 4.0 International” License. The purpose of SLaMA solver Frame is to cross-check by hand or spreadsheet calculations. This software is supplied “AS IS” without any warranties and support. The Author assumes no responsibility or liability for the use of the software. The Author reserves the right to make changes in the software without notification. The Author also make no representation or warranty that such application will be suitable for the use selected by the user without further calculations and/or checks.


Roberto Gentile is a Lecturer in Crisis and Catastrophe Modelling at IRDR.


Bianchi, Ciurlanti, and Pampanin. (2019). A SLaMA-Based Analytical Procedure for the Cost/Performance-Based Evaluation of Buildings. In COMPDYN 2019 – 7th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering. Crete Island, Greece.

Del Vecchio, Gentile, Di Ludovico, Uva, and Pampanin. (2018). Implementation and Validation of the Simple Lateral Mechanism Analysis (SLaMA) for the Seismic Performance Assessment of a Damaged Case Study Building [Open Access]. Journal of Earthquake Engineering 24 (11): 1771–1802. https://doi.org/10.1080/13632469.2018.1483278.

Gentile (2017). Extension, refinement and validation of the Simple Lateral Mechanism Analysis (SLaMA) for the seismic assessment of RC structures. PhD thesis. Polytechnic university of Bari, Italy.

Gentile, Pampanin, Raffaele, and Uva. (2019). Analytical Seismic Assessment of RC Dual Wall/Frame Systems Using SLaMA: Proposal and Validation [Open Access]. Engineering Structures 188: 493–505. https://doi.org/10.1016/j.engstruct.2019.03.029.

Gentile, Pampanin, Raffaele, and Uva. (2019). Non-Linear Analysis of RC Masonry-Infilled Frames Using the SLaMA Method: Part 1—Mechanical Interpretation of the Infill/Frame Interaction and Formulation of the Procedure [Open Access]. Bulletin of Earthquake Engineering 17 (6): 3283–3304. https://doi.org/10.1007/s10518-019-00580-w.

Gentile, Pampanin, Raffaele, and Uva. (2019). Non-Linear Analysis of RC Masonry-Infilled Frames Using the SLaMA Method: Part 2—Parametric Analysis and Validation of the Procedure [Open Access]. Bulletin of Earthquake Engineering 17 (6): 3305–26. https://doi.org/10.1007/s10518-019-00584-6.

Gentile, Del Vecchio, Pampanin, Raffaele, and Uva. (2019). Refinement and Validation of the Simple Lateral Mechanism Analysis (SLaMA) Procedure for RC Frames [Open Access]. Journal of Earthquake Engineering. https://doi.org/10.1080/13632469.2018.1560377.

New Zealand Society for Earthquake Engineering (NZSEE). (2006). Assessment and improvement of the structural performance of buildings in earthquakes. Wellington, New Zealand.

New Zealand Society for Earthquake Engineering (NZSEE). (2017). The Seismic Assessment of Existing Buildings – Technical Guidelines for Engineering Assessments. Wellington, New Zealand.

Pampanin. (2017). Towards the Practical Implementation of Performance-Based Assessment and Retrofit Strategies for RC Buildings: Challenges and Solutions. In SMAR2017- Fourth Conference on Smart Monitoring, Assessment and Rehabilitation of Structures. 13-15 March 2017. Zurich, Switzerland.


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