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Archive for January, 2022

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

r.gentile@ucl.ac.uk18 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.


References

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.

 

Seeing and Hearing: Underrated Skills?

David Alexander10 January 2022

There are two things we don’t teach our students but we should: to see and to listen. They are virtues–and skills–that are at least as important as writing and speaking. Some would argue that they are even more important. Pierre Bonnard, the great post-Impressionist painter, said that “many people look, but few see”. How very true! It is one thing to receive a visual impression and quite another to interpret it.

The island of Capri seen from the slopes of Mount Vesuvius (photo: D. Alexander).

For those of us who are in London, a good exercise is to catch the no. 9 bus at Aldwych, go upstairs (it is a double-decker) and travel at least as far as Knightsbridge, if not all the way to Hammersmith. Try it and look up: on the buildings of London there is a wealth of detail that is hard, and sometimes impossible, to see from ground level. There is an astonishing variety of statuary and ornamentation. It is part of the language of architecture through the ages, and its vocabulary is very rich indeed.

It is estimated that, thanks to electronic media, we come into contact with up to 70,000 images a day. Most of them are seen only fleetingly and few of them convey their full message to us. These days it is impossible not to be blasé about imagery. Contrast that with the situation in past ages, when people would travel long distances to view and marvel over a single image. In Florence in 1504, when Michelangelo Buonarroti finished his statue of David, he had it hauled into Piazza della Signoria and left in front of the city hall, Palazzo Vecchio. People came from far and wide to attach the Renaissance equivalent of ‘Post-It’ notes to the pedestal to express what they thought of the work (Forcellino 2009, p. 60). Despite the immense outpouring of creativity in Florence in that period, people were not satiated with images. They had time to weigh up and discuss each one.

Spending many hours each day staring at a small screen we run the risk of suffering from visual illiteracy. Under the constant bombardment of imagery, attention spans easily diminish. More does not mean better. Who now has time to acquire the skills to interpret images? Who now reads, for example, On Growth and Form, or The Story of Art, or The Four Books of Architecture?

To hear a recording of Artur Rubinstein (1887-1982) playing Robert Schumann’s Carnaval is to experience the perfect balance between precision and expression, for Rubinstein was one of the greatest pianists ever. It needs intense self-discipline to acquire that experience: absolute freedom from distraction, even breathing, stillness, perfectly maintained attentiveness. Only then does Rubinstein’s magic work its full wonders. None of these qualities is encouraged by electronic media; indeed, quite the reverse.

We who work or study in universities have one great mission: to interpret the human condition and communicate our findings. This is the acquisition of wisdom, which the OED defines, succinctly, as “soundness of judgement”. Hence, by definition wisdom is the opposite of superficiality. It follows that the quality of the output–shared wisdom–is a function of the quality of the input, the experience and interpretation of knowledge. Fuelling this are the impressions we receive as we live our lives, study and work.

Such is the cacophony of modern life that it may well be true that there is greater virtue  in listening than in speaking. It is never too late to learn to see and hear, to interpret space, form, sound and nuance. Nonetheless, we go to conferences to speak, not to listen. We tap away at the keyboard to write, not to read. This is perhaps not surprising given that the amount of material available to us to absorb is simply overwhelming. The Information Technology Age is of course still very young and it remains to be seen how humanity will cope with it and reach some kind of reconciliation. But as we make our uneasy progress through the ICT revolution, it is time to return to the old skills and develop our ability to understand the many languages of the visual and audible world around us.

References

Forcellino, Antonio 2009. Michelangelo: A Tormented Life. Polity Press, Cambridge UK, 344 pp.

Gombrich, Sir Ernst Hans Josef 1950. The Story of Art. Phaidon Press, London, 688 pp.

Palladio, Andrea 2000. The Four Books of Architecture (I quattro libri dell’architettura, 1570). Dover Press, New York, 110 pp.

Thompson, D’Arcy Wentworth 1942. On Growth and Form (2nd edition). Cambridge University Press, Cambridge, 1116 pp.

Rubinstein, Artur, 2016. Schumann: Carnaval, Op. 9 & Fantasiestücke, Op. 12. RCA, New York (CD).


David Alexander is Professor of Risk and Disaster Reduction at IRDR.