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Engineering analysis and design software

LUSAS IMDPlus software option

Bridge

Software option for

LUSAS Interactive Modal Dynamics (IMDPlus) – For rail use

Account Manager NameJob Title, LUSAS

Software Option

What is IMDPlus?

• IMDPlus extends IMD techniques available in all LUSAS products

– These only model a single loading event in a single direction• IMDPlus solves multiple loading events and advanced loading

condition in the time domain. • Applicable to 2D and 3D structures with 3 primary uses:

– Moving load analyses– Moving mass and moving sprung mass analyses– Seismic response based on support acceleration time histories


IMDPlus

• If dynamic response remains linear then the full response can be represented through modal superposition methods

• IMDPlus has the following assumptions inherent to modal superposition methods

– Linear in terms of geometry, material properties and boundary conditions

– No cross-coupling of modes (reasonable for all but the most highly damped structures)

– Low modes of vibration dominant– Damping ratios below critical damping


IMDPlus Moving Load Analyses

• Load defined by either– Complete layout definition– Composite axle definition (useful for train loading where the wheel loads

remain at a constant separation)– Composite axle also allows multiple trainset configurations to be analysed

with minimum effort

• Single speed or speed ranges can be solved in one analysis• Output available:

– Time histories; Peak summaries– Secondary Response Spectra (SRS); Modal combinations


Simple Shell Bridge


Shell Bridge – 3 Lowest Modes


Response of Mid-Span Edge


Envelopes over Speed Range

• Envelope any entity over analysis speed range– Worst acceleration at ~210 kph and > 300 kph


Steel Girder Bridge – Full Modelling

• Full bridge modelling including:– All steelwork– Bridge bearings– Ballast and track


Steel Girder Bridge

• Full complement of results could be extracted such as:

– Displacements– Velocities– Accelerations– Forces in the track system– Stresses and strains in the

steel girders


Newark High Speed Rail Bridge, UK


Step-By-Step Moving Load Analysis

• IMDPlus – Solves moving load analyses using modal superposition

• LUSAS includes implicit step-by-step dynamic solutions– Can solve equivalent analysis by this method


Step-By-Step Dynamics Example

• Elevated track model– Majority of structure

modelled using beams and shells

– Local model around a column uses solid elements and is coupled to beam/shell model


Step-By-Step Moving Load Analysis


Taiwan High Speed Rail Project (300 kph)


Full Non-linear Step-By-step

• In addition to simple moving load analyses, more complex non-linear effects can be incorporated, for example

– Sprung / Unsprung masses– Boundary conditions (contact / slidelines)– Geometric (large deflection)– Material


Sample Carriage Model


Simple Non-Linear Large Contact

• The simple shell bridge will be used• Mass representation of carriages by blocks (more complex

sprung modelling possible)• Contact modelled between ‘carriages’ and structure• Large deflection considered


Simple Non-Linear Contact

• Path


Simple Non-Linear Contact

• Displacement response


Seismic Analyses

• Spectral Methods (Modal Frequency Domain), e.g. SRSS and CQC

• IMDPlus (Modal Time Domain)• Step-By-Step Implicit Dynamics

– Linear effects– Non-linear boundary, geometric and material effects


IMDPlus - Seismic

• Input in form of support acceleration records (multiple earthquakes can be analysed in one analysis)

• Output available:– Time histories– Peak summaries (individual EQ and overall)– Secondary Response Spectra (SRS)– Modal combinations


Simple Shell Bridge - Seismic

• Bridge subjected to 10 second seismic event– Displacement and acceleration behaviour of the deck of interest– Also bending moments in the piers



• Displacement and acceleration records for edge of deck (mid-span)



• Lateral moments


Step-By-Step Implicit Dynamics

• Seismic analysis of a dock caisson


IMDPlus: In Summary

• LUSAS allows the analysis of complex dynamic systems• IMDPlus specifically provides analysis of moving load, moving

sprung mass and seismic events using modal superposition methods

• Advanced nonlinear features such as– Boundary effects (contact)– Geometric effects (large deformation)– Material effects (yield, bridge bearings/seismic isolators)


Engineering analysis and design software

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Civil and Structural engineering

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Specialist Applications

General mechanical engineering

Teaching and Research

Find out more at www.lusas.com

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