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    Run Response Spectrum Analysis with Nonlinear Soil Springs

    No more updating secant stiffness by hand. Set a tolerance, click run, and Civil NX iterates the p-y springs until they converge.

    Date
    Sep 16, 2026Wednesday
    Time
    1:00 – 2:00 PM EST10:00 – 11:00 AM PST
    Credit
    1 PDHLive attendance required
    Register now

    Live online session with open Q&A. Recording sent to everyone who registers.

    Secant stiffness, iteration by iteration

    Spring stiffness updates from computed displacement until it lands inside your tolerance band.

    Iterative response spectrum analysis in Civil NX, showing secant stiffness updating across iterations

    Session Overview

    Response spectrum analysis can't run with nonlinear springs. So you run it, read the displacements, update every spring by hand, and run it again - several rounds to converge one case, repeated for every load case.

    Civil NX now runs that loop for you. You set a tolerance, click run, and it recalculates secant stiffness from the p-y curve until the change falls inside it.

    In this hour we build p-y springs from borelogs, run the iterative response spectrum analysis live, and check the converged stiffness against a hand iteration, step for step.

    Already in Civil NX. No add-on module, no separate license.

    Learning Objectives

    By the end of the hour you'll be able to set up and defend an automatically converged response spectrum analysis in your own model.

    • Read the code requirement correctlySeparate what AASHTO LRFD Seismic actually mandates from what state seismic guides prescribe about secant stiffness in RSA.
    • Build p-y springs in the bridge modelDefine nonlinear soil springs from borelog data without exporting the substructure to a separate geotechnical program.
    • Set a tolerance and let it convergeConfigure the equivalent linearization loop so secant stiffness updates itself each iteration instead of by hand.
    • Verify the converged answerUse the iteration history to show a reviewer that the automated result matches a manual check, step for step.

    Key Features

    Civil NX processes point springs, extracts displacement results, and updates stiffness iteratively until convergence - then hands you the full history to compare.

    Automated iterative stiffness updates

    Stiffness values update iteratively until they converge on your tolerance. You start the run once instead of restarting it five times.

    Point spring processing

    Point springs are read and processed directly from the model, so nothing has to be exported, edited, and imported back.

    Displacement results extraction

    Displacements come straight out of the analysis and drive the next stiffness value - no copying numbers between windows.

    Stiffness evolution tracking

    Track how each spring's stiffness moved across iterations. That trace is what you hand a reviewer asking how the value was reached.

    Presented By

    Dev Bhararia

    Dev Bhararia

    Structural Engineer, MIDAS

    Dev holds a Master's degree in Structural Engineering from SVNIT Surat and brings valuable experience from working on a wide range of bridge and building projects. His background includes both design and on-site execution, giving him a well-rounded perspective of structural systems. Dev is particularly enthusiastic about addressing complex engineering challenges and enhancing structural safety and efficiency.

    Event Agenda

    50 minutes of presentation and live demo, then 10 minutes of open Q&A. All times EST.

    1. 1:00 – 1:05 PM 5 min Why this became manual workThe gap between what the code asks for and what an RSA solver can do with nonlinear springs.
    2. 1:05 – 1:50 PM 45 min Code basis, live demo, and verificationAASHTO LRFD Seismic and state guidance, the iterative response spectrum workflow in Civil NX, and converged results checked against a hand iteration.
    3. 1:50 – 2:00 PM 10 min Live Q&ABring your model conditions. Questions submitted during registration go first.

    Attend the full live session to receive 1 PDH. Certificates are emailed within five business days.

    The Rest of the Series

    Four more sessions this fall. Registration opens closer to each date - attend this one and you'll hear about them first.

    • Sep 22, 2026
      Parametric Modeling with Grasshopper
      Enhance your parametric modeling and analysis workflow
      Register
    • Oct 7, 2026
      Field Splice Sheets Integration
      The MIDAS Connector, an Excel add-in, live-links section properties and force results straight from your Civil NX model into whatever sheet you already run.
      Registration opens soon
    • Oct 28, 2026
      MIDAS across the Bridge Lifecycle
      One MIDAS model follows the bridge from planning through demolition.
      Registration opens soon
    • Nov 11, 2026
      Project Application Presentation
      Registration opens soon

    Save Your Seat

    One model for seismic analysis, design, and rating - now with nonlinear soil, automatically converged.