LARSA 4D
Overview
LARSA 4D is the leading solution for advanced staged construction and time-dependent analysis of bridge and building projects. Based on the most well respected 3D analysis engine in our field for two decades, and with an intuitive and modern user interface, LARSA 4D is an essential tool for any construction project.
LARSA 4D has been used on the most demanding projects, including cable-stayed, suspension, and stressed-ribbon bridges, domes, and building structures with unusual requirements.
For additional information beyond what can be found below, please see our brochures and other downloads.
What is “4D”?
Time — the fourth dimension — is the focus of LARSA 4D. LARSA 4D’s Staged Construction Analysis delivers on both power and productivity. Construction analysis models the step-by-step activities that will take place to build the structure. LARSA 4D’s construction analysis is a fully nonlinear analysis (both material and geometric) with time-dependent material effects such as creep and shrinkage and load class tracking for every construction activity. Analysis scenarios — pushover, collapse, and live load — at any point in the construction sequence reduce man-hours by producing all needed results in a single project run.
LARSA 4DLARSA 4D is an industry leader
Advanced features in LARSA 4D include nonlinear analysis with two methods of geometric nonlinearity, 3D post-tensioning tendons, seismic and inelastic hysteretic elements, seismic and dynamic analysis such as nonlinear time history with the full Newton-Raphson method, bridge geometry coordinate systems, influence line and surface live load analysis, and staged construction analysis. LARSA 4D is integrated tightly with LARSA Section Composer for parametric and nonprismatic section analysis and the Steel Girder Design Module for AASHTO LRFD code check.
Client Base
LARSA software is the company standard at FIGG, HDR, International Bridge Technologies, Parsons Brinckerhoff, Parsons Transportation Group, TYLIN International, and is a standard in many offices of leading firms including Halcrow and TGP in the UK, SYSTRA in France, and Yüksel Proje in Turkey.
Advanced Power with LARSA 4D
4D Staged Construction Analysis
Time is the focus of LARSA 4D because complex structures and segmental bridges are built in discrete stages. LARSA 4D was one of the first analysis programs to include a Staged Construction Analysis with time-dependent material properties, but year after year our software updates deliver the cutting edge.
- Construction activities include construction and deconstruction of members, plates, springs, and foundation elements, loading, temporary/traveler loads, support and constraint changes, displacement initializations, hoist for incremental launching, hinged/matched cast joint initialization for segmental construction, tendon stressing and slackening, and post-tensioning stay cables.
- Geometric nonlinearity is included.
- Time-dependent material properties include creep, shrinkage, time effect on elastic modulus, relaxation, and effects of superimposed loads.
- Cumulative, incremental, and partial load-class results. Partial load-class results are required for code-based combinations and support the “destructive” activities: support, constraint, and element removal.
- Analysis scenarios: At any stage during construction, additional analyses can be performed. These analyses continue based on the deformed state of the structure at that stage.
- Tendons: internal and external, pre- and post-tensioning. Tendons are truly 3D and include short-term (wobble and curvature friction and anchorage slip) and long-term material losses (relaxation).
User Interface
LARSA 4D’s user interface is easy to learn and quick to use. Its spreadsheets and graphics are better and faster than ever before. LARSA 4D also has infinite-level undo/redo, macro integration with Microsoft Excel, and integrity checks, making it easy for users to correct those inevitable mistakes. Modeling tools include meshing, extrusion, parametric templates, and CAD-like drawing tools.
Analysis Types
- Linear Elastic Static & P-Delta Analyses
- Nonlinear Static Analysis
- Moving Load Analysis (marching vehicle)
- Linear & Nonlinear Time History Analysis
- Eigenvalue & Stressed Eigenvalue Analysis
- Response Spectrum Analysis
- Staged Construction Analysis
- Influence Line & Surface Live Load Analysis
- Plastic Pushover & Progressive Collapse Analysis
All analysis types make use of a fast sparse solver that takes advantage of multi-core/multi-CPU computers.
The Nonlinear Time History Analysis is an extension to its linear counterpart, computing the response of a structure to time-dependent loads taking into account geometric and material nonlinearity. This analysis is invaluable for cable-stayed and suspension bridge projects, in which nonlinearity plays a vital role. The analysis is carried out by using a combination of the Newmark-Beta time integration algorithm and either full or modified Newton-Raphson method, using iterations within each integration time-step.
Plastic Pushover Analysis is a simplified form of progressive collapse. Plastic pushover performs a nonlinear inelastic analysis on a load case, continuously loading the structure until a stopping criterion is met. The criterion is a maximum displacement at a particular joint in a particular direction. The progressive collapse analysis uses arc length and auto-stepping for post-buckling strength, and is made more powerful by LARSA’s inelastic element library.
The basic element library includes beam, truss, cable, grounded foundation springs, two-node springs, coupled general 6x6 stiffness elements, hook and gap elements, plates, shells, membrane elements, and lumped masses for dynamic analysis. Special element features include:
- Cable element rebirth
- Prestressing and post-tensioning loading for cable elements
- User coordinate systems on spring elements for arbitrary directions
- Thick plate element.
- Nonprismatic cross-section variation (haunches) using Section Composer.
Inelastic Elements
The nonlinear analysis of structures has become increasingly important in the study of structural response to hazardous loading such as earthquake and blast.
- Uniaxial Hysteretic Spring with a polygon hysteretic model and with strength and stiffness degradation capabilities
- Connection Beam Element, an elastic beam with built-in yielding springs at the ends.
- Hysteretic Beam
- Triaxial Hysteretic Spring
- Yield-Surface Beam Element
LARSA has worked with the earthquake research group MCEER at the University at Buffalo to bring the latest nonlinear earthquake analysis technologies into mainstream use by integrating their research into the already user friendly analysis environment that LARSA provides.
Geometry Control
The Bridge Path User Coordinate System is a tool of convenience for modeling, allowing the user to work in very simple coordinates despite any curvature of the structure. This is accomplished by warping the usual x-axis into a curve that follows the curved centerline of the bridge.
The Model Optimization tools determines how to prestress cables when they are installed so that the deformed geometry of the model, such as a cable or deck profile, matches a desired target. Two iterative methods are available. Used with Staged Construction Analysis, it takes into account the construction sequence, nonlinearity, and long-term material time effects.
Results Tools
Tools such as Linear Result Combinations and Extreme Effect Groups make post-processing faster by allowing advanced manipulations of data within the program without the need to re-run an analysis. Linear Result Combinations can be used to create a factored load combination after an analysis has been completed by adding together the results of solved load cases as they are requested. Linear Result Combinations become regular result cases with which all of the usual results tools can be used, including graphics, spreadsheets, and graphs. Extreme Effect Groups allow the user to set up result cases that represent the “worst case” out of a group of cases. They are like saved envelopes. These groups always report the minimum and maximum values from a group of cases, enveloping over a particular result.
Analysis results can be viewed both graphically and numerically. Graphical results include deformed model, reactions, member forces and stresses, plate deformations, forces, and stresses, and plastic yield. Results can be shown for the total cumulative effect or, in Staged Construction Analysis, for the incremental effect of a stage’s loading or for the cumulative effect of just a single load class.
Macros: Program Flexibility
Whenever you’re faced with a repetitive task, let your computer do the work for you. LARSA 4D macros can automate any program process to save time, including data import, modeling, and results analysis & export.
Macros can be written within Microsoft Excel (Microsoft Office VBA) or any COM-enabled programming language. While some programming experience is generally needed to write macros from scratch, our technical support staff gladly writes macros and helps our clients develop and modify macros. LARSA 4D’s macro API or “object model” was built in to the program from the very start and the thousands of classes and methods in the public API create infinite possibilities for macro writers. Here are some:
- Load joint coordinates and other geometry from an Excel worksheet, or any other custom data format.
- Use Excel to input model parameters, and then write a macro to assemble the repetitive parts of the structure programmatically.
- Create entire models with a macro to facilitate parametric analysis.
- Copy and transform parts of the structure according to custom rules.
- Edit and convert thousands of existing model objects at once. Results
- Post-process analysis results according to project-specific criteria in a macro, without copy-pasting to Excel.
- Export result data to other applications.
- Use a macro to perform iterative form- finding by automating the process of running an analyis, extracting results, and updating model geometry or loading. Macros can read all results and can update any aspect of model data.