CSiBridge Features

User Interface

One Window, Many Views

CSiBridge offers a single user interface to perform: Modeling, Analysis, Design, Scheduling, Load Rating, and Reporting.



CSiBridge offers a selection of templates for quickly starting a new bridge model or structure. This is often a good starting point to creating a model as the template can be modified later.

Interactive Database Editing

Interactive database editing allows users to edit model data in a table view which simplifies the task of making changes to the model. Tables are easily exportable and importable from Microsoft Excel and Microsoft Access.

Parametric Bridge Modeling

Bridge Object Model

The bridge object model is a comprehensive assemblage of components that make up the entire bridge model. The parametric model is managed through the bridge object model. This includes: the modeling of deck sections, diaphragms, bearings, restrainers, foundation springs, superstructure variation, abutments, bents, hinges, tendon layouts, and more.

Bridge Wizard

The Bridge Wizard is a powerful tool that guides users step-by-step through the creation of a complete bridge model with instructions at each step to ensure that all of the necessary components are defined in the model.

Layout Lines

Layout lines define the the highway layout of the bridge. They can be defined within CSiBridge using bearing and station notation, or they can be imported using a TransXML file. As layout lines are modified, the entire bridge structure and its parametric geometry is updated.

Superstructure Deck Sections

CSiBridge has a wide array of parametric deck sections including concrete box girders, precast I and U girders, steel boxes, and steel girder bridges. All deck sections are parametrically configurable for an accurate bridge deck section definition.


Bridge substructures can very accurately be modeled in CSiBridge. Bents, abutments, restrainers, bearings and foundation springs are all elements that can be defined as either link or hinge elements.


Diaphragms may be located at the supports and along the spans. Types include concrete, steel girder, and detailed steel cross-frames. These may be skewed and staggered. Interior cross frames for steel U-girders may also be specified.


Define post-tensioning in CSiBridge using the refined options for laying out tendons and forces. When defining box girders, CSiBridge will automatically assign the drape locations within the tendon; the engineer can edit them as well.

Parametric Variations

CSiBridge allows variations for the entire bridge or just parts of the bridge alignment and slope, for both horizontal or vertical variations of the deck section. Defining variations parametrically significantly reduces the amount of time spent on the modeling process.


Quickly define the lanes based on the layout lines of the bridge. The lanes can be defined such that the width of each lane is wider than the design vehicle. Enveloped response results can be defined later to accurately model vehicle loads on the bridge.

Structural Components


CSiBridge automatically creates joints at structural object intersections or internal joints when meshing structural objects. Joint coordinates and information may be displayed on screen in the model window or in tabular format.


The frame element uses a general, three-dimensional, beam-column formulation which includes the effects of biaxial bending, torsion, axial deformation, and biaxial shear deformations. CSiBridge has a built-in library of standard concrete, steel, and composite section properties of both US and International Standard sections.

Intermediate joints will automatically be generated where other members intersect with the frame to ensure finite element connectivity.

Even non-prismatic and built up steel sections can be easily defined. Use our Section Designer for more complex sections.


In CSiBridge, Tendons are easily drawn as independent objects, with geometry specified as straight lines, parabolas, circular curves, or other arbitrary shapes. They can also be defined parametrically to drape inside of a box girder. Tendon loads, including all losses, are easily defined.


The cable element is a highly nonlinear element used to model the catenary behavior of slender cables under their own self-weight. They are particularly useful in modeling suspension bridges or cable-stayed bridges.


The shell element is a type of area object that is used to model membrane, plate, and shell behavior in planar and three-dimensional structures. The shell material may be homogeneous or layered throughout; material nonlinearity can also be considered when using the layered shell.


The solid element is an eight-node element for modeling three-dimensional structures and solids. It is based upon an isoparametric formulation that includes nine optional incompatible bending modes and is useful for modeling objects in which loading, boundary conditions, section properties, or reactions vary by thickness.


A link element may exhibit linear, nonlinear, and frequency dependent behavior. The following link elements are available in CSiBridge: Linear, Multi-linear Elastic, Multi-linear Plastic, Gaps, Hooks, Dampers, Friction Isolators, Rubber Isolators, T/C Isolators, Frequency-dependent Springs, and Frequency-dependent Dampers.


Users can create and apply hinge properties to perform pushover analyses in CSiBridge. Nonlinear material behavior in frame elements (beam/column/brace) can be modeled using fiber hinges. This approach represents the material in the cross section as discrete points, each following the exact stress-strain curves of the material. Mixed materials, such as reinforced concrete and complex shapes can be represented.


Spring supports are link elements that are used to elastically connect joints to the ground and can be linear or nonlinear in nature. Nonlinear support conditions can be modeled to include gaps (compression only), multi-linear elastic or plastic springs, viscous dampers, and base isolators. Advanced modeling capabilities allow foundations to be included with the superstructure, including piles and spread footings. P-Y multi-linear force deformation parameters and compression-only soil springs can be defined.


Vehicle Loads and Classes

Vehicles are used to define the moving loads in CSiBridge and are most often defined to act on the traffic lanes. There are standard types of vehicles in the program, or users can design unique vehicles using the general vehicle specification. Vehicle classes are sets of one or more vehicles that can be assigned to act on lanes in a moving-load case.

Load Patterns

A load pattern is a specified spatial distribution of forces, displacements, temperatures, and other effects that act upon the structure.

Parametric Loading

Superstructure loads may be defined and assigned to a bridge object model parametrically. Bridge Object loads may be assigned for any defined load pattern type and may include loads due to wearing surfaces, parapets, forms, diaphragms, girders, decks and more. Once the parametric bridge object loads have been defined they may be easily displayed and modified.

Parametrically defined load assignments are preserved even when changes are made to the bridge object discretizations, deck types or alignments.

Temperature Load creates thermal strain in the element. This strain is given by the product of the material coefficient of thermal expansion and the temperature change of the element. All specified temperature loads represent a change in temperature from the unstressed state for a linear analysis, or from the previous temperature in a nonlinear analysis.



CSI Solvers have been tried and tested by the industry for over 35 years. The SAPFire Analysis Engine can support multiple 64-bit solvers for analysis optimization and perform both Eigen Analysis and Ritz Analysis.

Moving Load

Moving load analysis is available in CSiBridge to compute influence lines and surfaces for traffic lanes on bridge structures and to analyze these structures for the response due to vehicle live loads. Vehicles can also be moved in a multi-step analysis. This can use either multi-step static load cases or time-history load cases, the latter of which can be linear or nonlinear.


Linear (bifurcation) buckling modes of a structure can be found under any set of loads. Buckling can be calculated from a nonlinear or staged-construction state. Full nonlinear buckling analysis is also available considering P-delta or large deflections effects. Snap-through buckling behavior can be captured using static analysis with displacement control. Dynamic analysis can be used for modeling more complex buckling, such as follower-load problems.


P-delta analysis captures the softening effect of compression and the stiffening effect of tension. A single P-delta analysis under gravity and sustained loads can be used to modify the stiffness for linear load cases, which can later be superposed. Alternatively, each combination of loads can be analyzed for full nonlinear P-delta effects. P-delta effects are included for all elements and are seamlessly integrated into analysis and design.


Pushover analysis features in CSiBridge include the implementation of FEMA 356 and the hinge and fiber hinge option based on stress-strain. The nonlinear layered shell element enables users to consider plastic behavior of concrete shear walls, slabs, steel plates, and other area finite elements in the pushover analysis. Force-deformation relations are defined for steel and concrete hinges.


CSiBridge dynamic analysis capabilities include the calculation of vibration modes using Ritz or Eigen vectors, response-spectrum analysis, and time-history analysis for both linear and nonlinear behavior.

Eigen-vector modal analysis finds the natural vibration modes of the structure, which can be used for understanding the behavior of the structure, and also as the basis for modal superposition in response-spectrum and modal time-history load cases. Ritz-vector modal analysis finds the optimum modes for capturing structural behavior in response-spectrum and modal time-history load cases, and is more efficient for this purpose than Eigen-vector analysis.

Time-history analysis captures the step-by-step response of structures to seismic ground motion and other types of loading such as blast, machinery, wind, waves, etc. Analysis can use modal superposition or direct-integration methods, and both can be linear or nonlinear. The nonlinear modal method, also called FNA for Fast Nonlinear Analysis, is extremely efficient and accurate for a wide class of problems. The direct-integration method is even more general, and can handle large deformations and other highly nonlinear behavior. Nonlinear time-history analyses can be chained together with other nonlinear cases (including staged construction) addressing a wide range of applications.

Time Dependent

Staged construction is a type of nonlinear analysis in CSiBridge that allows you to define a sequence of stages wherein you can add or remove portions of the structure, selectively apply load to portions of the structure, and to consider time-dependent material behavior such as aging, creep, and shrinkage.

Staged construction is variously known as incremental construction, sequential construction, or segmental construction.

Long term deflections due to creep and shrinkage can be computed along with staged sequential construction analysis. Time dependent material properties are based upon the 1990 edition CEB-FIP code and user defined curves are used to compute creep strains.

Steady State

Steady state analysis is available to determine the response of the structure due to cyclic (harmonic, sinusoidal) loading over a range of frequencies. Frequency-dependent stiffness and damping (complex impedance) properties may be included for modeling foundations and far-field effects, including radiation damping. Steady state analysis can be used to measure the effects of multiple machines operating at different frequencies by combining the results of several analyses in the same model.

Target Force

During nonlinear static analysis, cable and frame elements can be automatically strained to achieve specified target axial force values. This is most commonly used to tighten cables to pre-specified tensions, but it can also be used to jack structures to a specified force using frame elements.

Load Combinations

CSiBridge allows for an unlimited number of load cases and combinations. Load combination types include: linear additive, envelope (min/max), absolute add, SRSS, and range combinations. Combination components can include other combinations.


Steel Frame

Fully integrated steel frame design includes member size optimization and implementation of design codes. CSiBridge allows users to interactively view design results at any frame member, change the parameters or section properties, and display the updated member results.

See supported design codes

Concrete Frame

Fully integrated concrete frame design in CSiBridge includes: required area of steel calculations, auto selection lists for new member sizing, implementation of design codes, interactive design and review, and comprehensive overwrite capabilities.

See supported design codes


CSiBridge will perform the superstructure design for the following bridge superstructure types and codes:

See supported design codes

Automated Seismic

Engineers can define specific seismic design parameters to be applied to the bridge model during an automated cycle of analysis through design. The new AASHTO seismic design specification has been incorporated into CSiBridge, including pushover analysis for seismic category D.

Load Rating

Load Rating Overview

CSiBridge load rating calculates the safe load capacity of a bridge based on the requirements of the AASHTO Manual for Condition Evaluation and Load and Resistance Factor Rating (LRFR) of Highway Bridges October 2003 with 2005 Interim Revisions and the Manual for Bridge Evaluation Second Edition 2011 with 2013 Interims.

Output and Display

Deformed Geometry

Users can display deformed geometry based on any load or combination of loads, as well as animations of modes.

Force Diagrams

Shear and moment diagrams display internal shear forces, moments, and displacements at all locations along the length of a frame element for any load case or load combination. CSiBridge gives the option to scroll along the length to display values or scroll directly to the maximum value location.

Bridge Reponses

In CSiBridge, moving load response is calculated for all joints and elements. For each of the following types of response, you may request a group of elements for which the response should be calculated: Joint displacements, Joint reactions, Frame forces and moments, Shell stresses, Shell resultant forces and moments, Plane stresses, Solid stresses and Link/support forces and deformations.

Influence Surfaces

An influence surface can be viewed as a curve of influence values plotted at the load points along a traffic lane. For a given response quantity (force, displacement, or stress) at a given location in the structure, the influence value plotted at a load point is the value of that response quantity due to a unit concentrated downward force acting at that load point.


CSiBridge allows users to animate results of vehicles and other loads on the bridge model to help understand bridge behavior. Create movie files showing time-history and moving vehicle responses, including multiple vehicles.


Report Generation

Pre-formatted printed reports are now available at the push of a button. These reports include all pertinent model data and the results of analysis and design. Data is presented in tabulated format, along with graphics, table of contents, and a cover sheet displaying project information and your company name and logo.


Load Optimizer

The load optimizer is a tool in CSiBridge to compute the optimal load application to achieve desired structural response. Loads may be applied linearly, nonlinearly, or in staged-construction. Goals and limits may include displacements, forces, moments, and more.

Section Designer

Section Designer is a utility that is built into CSiBridge. It allows users the ability to create specialized sections of any arbitrary shape and material, including rebar layout. All section properties, biaxial interaction diagrams, and moment curvature diagrams are automatically calculated.

Import and Export

Supported Formats

CSiBridge supports many industry standards for importing and exporting data. LANDXML, AutoCAD (DXF/DWG), CIS/2, IFC, and SDNF are all supported. CSiBridge also supports exporting of a model to an Microsoft Access database. If users are using other analysis packages, CSiBridge can import files from FrameWorks Plus, IGES, STAAD, and STRUDL.