{"id":101189,"date":"2026-04-24T17:09:50","date_gmt":"2026-04-24T17:09:50","guid":{"rendered":"https:\/\/geostru.ai\/en\/products\/rsl3\/"},"modified":"2026-07-08T12:34:23","modified_gmt":"2026-07-08T12:34:23","slug":"rsl3","status":"publish","type":"page","link":"https:\/\/geostru.ai\/fr\/products\/rsl3\/","title":{"rendered":"RSL III NX"},"content":{"rendered":"
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RSL III NX<\/h1>\n<\/div><\/div>\n\n

One-dimensional local seismic response analysis in the browser \u2014 propagate an accelerogram from bedrock to the surface through your soil column with the equivalent-linear method, and get response spectra, amplification and the ICMS microzonation factors, aligned with NTC 2018 and Eurocode 8.<\/p>\n<\/div><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n

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What it does<\/h2>\n<\/div><\/div>\n\n

RSL III NX takes a stratigraphic column and a bedrock accelerogram and returns the seismic motion at the surface \u2014 response spectra, amplification and the ICMS Level-3 microzonation factors \u2014 through an iterative equivalent-linear analysis, entirely in the browser.<\/p>\n<\/div><\/div>\n\n

Layered soil model<\/strong> \u2014 each layer by unit weight, small-strain shear-wave velocity Vs, damping and the degradation curves G\/Gmax-\u03b3 and \u03be-\u03b3 (Vucetic-Dobry, Seed-Idriss, Darendeli and custom).<\/p>\n<\/div><\/div>\n\n

Equivalent-linear analysis<\/strong> \u2014 an iterative scheme that converges on the effective shear strain, capturing the soil's nonlinear stiffness and damping.<\/p>\n<\/div><\/div>\n\n

Flexible input motion<\/strong> \u2014 imported accelerograms (PEER, ITACA, ESM, CSV), synthetically generated signals or built-in example records at bedrock.<\/p>\n<\/div><\/div>\n\n

Complete outputs<\/strong> \u2014 surface PGA, response spectra Sa(T), Sv(T) and Sd(T), the frequency amplification function, elastic and design spectra and the ICMS 2018 factors.<\/p>\n<\/div><\/div>\n\n

Seismic parameters built in<\/strong> \u2014 ag, F0 and Tc* from coordinates or address for every limit state (SLO, SLD, SLV, SLC).<\/p>\n<\/div><\/div>\n\n

Report-ready deliverables<\/strong> \u2014 Word reports for seismic microzonation and site-response studies.<\/p>\n<\/div><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n

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The equivalent-linear method<\/h2>\n<\/div><\/div>\n\n

The equivalent-linear method approximates the soil's nonlinear behaviour with a sequence of linear analyses, updating stiffness and damping until they match the strain the shaking actually produces.<\/p>\n<\/div><\/div>\n\n

Layer discretisation<\/strong> \u2014 the column is split into thin sub-layers and the transfer function H(\u03c9) is built from the plane-wave coefficients between base and surface.<\/p>\n<\/div><\/div>\n\n

Effective shear strain<\/strong> \u2014 each iteration takes the effective strain as \u03b3eff = 0.65 \u00b7 \u03b3max and reads the secant shear modulus and damping from the degradation curves.<\/p>\n<\/div><\/div>\n\n

Convergence<\/strong> \u2014 stiffness and damping are updated and the analysis repeats until the strain change is small \u2014 typically 4\u20138 iterations; many more points to a strongly nonlinear regime.<\/p>\n<\/div><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n

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Soil column and dynamic curves<\/h2>\n<\/div><\/div>\n\n

The reliability of a 1D analysis rests on the soil column and the curves that describe how each layer softens with strain.<\/p>\n<\/div><\/div>\n\n

Layer parameters<\/strong> \u2014 thickness, unit weight \u03c1, small-strain velocity Vs and the maximum shear modulus Gmax = \u03c1 \u00b7 Vs\u00b2, with a baseline damping \u03bemin.<\/p>\n<\/div><\/div>\n\n

Degradation curves<\/strong> \u2014 G\/Gmax-\u03b3 and \u03be-\u03b3 from established models \u2014 Vucetic-Dobry (1991) for clays by plasticity index, Seed-Idriss (1970) for sands, Darendeli (2001) \u2014 or your own tabular data.<\/p>\n<\/div><\/div>\n\n

Bedrock<\/strong> \u2014 the deepest layer is the seismic bedrock (Vs \u2265 800 m\/s), so the 1D wave propagation is anchored to a rigid base.<\/p>\n<\/div><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n

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Input motion<\/h2>\n<\/div><\/div>\n\n

The analysis is driven by the reference accelerogram at bedrock and by how you combine the records.<\/p>\n<\/div><\/div>\n\n

Real records<\/strong> \u2014 import accelerograms in PEER, ITACA, ESM or CSV format; the app reads the time step \u0394t and the duration automatically.<\/p>\n<\/div><\/div>\n\n

Synthetic signals<\/strong> \u2014 generate spectro-compatible motions by band-pass FFT filtering with a seismic envelope, or start from the built-in example records.<\/p>\n<\/div><\/div>\n\n

Analysis type<\/strong> \u2014 single site and record, multi-input (several accelerograms averaged per NTC 2018) or multi-site comparison of stratigraphies.<\/p>\n<\/div><\/div>\n\n

Code guidance<\/strong> \u2014 NTC 2018 asks for at least seven spectro-compatible accelerograms; prepare and scale them in GeoStru Spectra or REXEL, as RSL III does not rescale automatically.<\/p>\n<\/div><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n

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How it works<\/h2>\n<\/div><\/div>\n\n

A guided flow takes you from the soil column to an exported report in seven steps.<\/p>\n<\/div><\/div>\n\n

1 \u00b7 Stratigraphy<\/strong> \u2014 define each layer's thickness, Vs, density and damping and pick its degradation curves; close the column on bedrock (Vs \u2265 800 m\/s).<\/p>\n<\/div><\/div>\n\n

2 \u00b7 Dynamic curves<\/strong> \u2014 assign the G\/Gmax and damping curves per layer, from the library or from your own data.<\/p>\n<\/div><\/div>\n\n

3 \u00b7 Input accelerogram<\/strong> \u2014 load the bedrock motion (PEER, ITACA or CSV); the time step and duration are detected automatically.<\/p>\n<\/div><\/div>\n\n

4 \u00b7 Analysis type<\/strong> \u2014 single-site, multi-input or multi-site.<\/p>\n<\/div><\/div>\n\n

5 \u00b7 Equivalent-linear computation<\/strong> \u2014 the app builds the transfer function, estimates \u03b3eff = 0.65 \u00b7 \u03b3max and iterates the stiffness and damping to convergence.<\/p>\n<\/div><\/div>\n\n

6 \u00b7 Results<\/strong> \u2014 the response spectrum against the NTC 2018 reference, the input\/output Fourier spectra, the \u03b3max(z), amax(z) and \u03c4max(z) profiles and the ICMS amplification factors.<\/p>\n<\/div><\/div>\n\n

7 \u00b7 Export<\/strong> \u2014 a Word report for the microzonation or site-response study.<\/p>\n<\/div><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n

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Inputs and outputs<\/h2>\n<\/div><\/div>\n\n

What you enter<\/h3>\n<\/div><\/div>\n

Soil column<\/strong> \u2014 layer thickness, unit weight, Vs and damping, with the degradation curves.<\/p>\n<\/div><\/div>\n\n

Input motion<\/strong> \u2014 the bedrock accelerogram(s), imported or synthetic.<\/p>\n<\/div><\/div>\n\n

Site<\/strong> \u2014 coordinates or address, so ag, F0 and Tc* are retrieved for every limit state.<\/p>\n<\/div><\/div>\n\n

What you get<\/h3>\n<\/div><\/div>\n

Response spectra<\/strong> \u2014 Sa(T), Sv(T) and Sd(T) at the surface, against the NTC 2018 reference.<\/p>\n<\/div><\/div>\n\n

Amplification<\/strong> \u2014 the frequency transfer function and the ICMS 2018 factors (FA, FH, FT).<\/p>\n<\/div><\/div>\n\n

Depth profiles<\/strong> \u2014 the maximum shear strain \u03b3max(z), acceleration amax(z) and shear stress \u03c4max(z).<\/p>\n<\/div><\/div>\n\n

Deliverables<\/strong> \u2014 a Word report for microzonation and site-response studies.<\/p>\n<\/div><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n

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Who it's for<\/h2>\n<\/div><\/div>\n\n

Geologists \u00b7 Geotechnical and seismic engineers \u00b7 Consulting firms. RSL III NX is for anyone who runs site-specific ground-response analyses \u2014 for seismic microzonation, building design on soft soils and seismic hazard assessment \u2014 and wants a single web tool that goes from the soil column and the bedrock motion to code-ready surface spectra and amplification factors.<\/p>\n<\/div><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n

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Why it's different<\/h2>\n<\/div><\/div>\n\n

Runs directly in the browser \u2014 no installation, always up to date.<\/p>\n<\/div><\/div>\n\n

A full equivalent-linear 1D analysis with the standard degradation-curve library built in.<\/p>\n<\/div><\/div>\n\n

Real, synthetic and multi-record input motions, with single-site, multi-input and multi-site analyses.<\/p>\n<\/div><\/div>\n\n

Surface spectra, the amplification function and the ICMS 2018 factors in one place.<\/p>\n<\/div><\/div>\n\n

Seismic hazard parameters (ag, F0, Tc*) retrieved automatically for every limit state.<\/p>\n<\/div><\/div>\n\n

Word reports ready for a Level-3 seismic microzonation study.<\/p>\n<\/div><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n

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Frequently asked questions<\/h2>\n<\/div><\/div>\n\n

What does "equivalent-linear" mean?<\/strong>
It approximates the soil's nonlinear response with a sequence of linear analyses, updating stiffness and damping at each iteration until they match the strain the shaking produces.<\/p>\n<\/div><\/div>\n\n

Where do the Vs velocities come from?<\/strong>
From direct seismic measurements \u2014 MASW, ReMi, cross-hole, down-hole or SCPT; empirical SPT correlations are too uncertain for a reliable analysis.<\/p>\n<\/div><\/div>\n\n

How deep should the column go?<\/strong>
Down to the seismic bedrock (Vs \u2265 800 m\/s), typically between 5 and 300 m in Italy.<\/p>\n<\/div><\/div>\n\n

How many accelerograms do I need?<\/strong>
NTC 2018 asks for at least seven spectro-compatible records; RSL III does not rescale them, so prepare them in GeoStru Spectra or REXEL.<\/p>\n<\/div><\/div>\n\n

Which amplification factor should I use?<\/strong>
FA for low-rise buildings, FH for mid-rise, and the full spectrum for tall structures.<\/p>\n<\/div><\/div>\n\n

Does it compute post-seismic settlements?<\/strong>
No. RSL III covers ground response; for liquefaction and settlements use LiquiTer NX.<\/p>\n<\/div><\/div>\n<\/div>\n<\/div>\n<\/div>\n\n

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Ready to start with RSL III NX?<\/h2>\n<\/div><\/div>\n\n

Choose your plan and start using RSL III NX today. Runs in the browser, always up to date, no installation required.<\/p>\n<\/div><\/div>\n\n\n\n\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":0,"featured_media":101188,"parent":101181,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_ai_seo_pilot_schema_type":"auto","footnotes":""},"class_list":["post-101189","page","type-page","status-publish","has-post-thumbnail","hentry"],"_links":{"self":[{"href":"https:\/\/geostru.ai\/fr\/wp-json\/wp\/v2\/pages\/101189","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/geostru.ai\/fr\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/geostru.ai\/fr\/wp-json\/wp\/v2\/types\/page"}],"replies":[{"embeddable":true,"href":"https:\/\/geostru.ai\/fr\/wp-json\/wp\/v2\/comments?post=101189"}],"version-history":[{"count":2,"href":"https:\/\/geostru.ai\/fr\/wp-json\/wp\/v2\/pages\/101189\/revisions"}],"predecessor-version":[{"id":102102,"href":"https:\/\/geostru.ai\/fr\/wp-json\/wp\/v2\/pages\/101189\/revisions\/102102"}],"up":[{"embeddable":true,"href":"https:\/\/geostru.ai\/fr\/wp-json\/wp\/v2\/pages\/101181"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/geostru.ai\/fr\/wp-json\/wp\/v2\/media\/101188"}],"wp:attachment":[{"href":"https:\/\/geostru.ai\/fr\/wp-json\/wp\/v2\/media?parent=101189"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}